INDUSTRY PRACTICE STANDARDS

AND

DFI PRACTICE GUIDELINES

FOR

STRUCTURAL SLURRY WALLS

DEEP FOUNDATIONS INSTITUTE

First EditionCopyright 2005

Prepared by

INDUSTRY PRACTICE STANDARDSAND

DFI PRACTICE GUIDELINESFOR

STRUCTURAL SLURRY WALLS

First Edition

DFI – Deep Foundations Institute326 Lafayette Avenue

Hawthorne, NJ 07506 USAwww.dfi.org

May 10, 2005

BY DFI SLURRY WALL/TRENCH COMMITTEE

Copyright 2005

All Rights Reserved

This book or any part thereof must not be reproduced in

any form without the written permission of the publisher.

Printed in USA

PREFACE

This publication of the Deep Foundations Institute (DFI) is intended to providethe industry with model practice guidelines for design and construction ofstructural slurry walls. It does not represent a design document, nor does itprovide a pre-engineered slurry wall specification; rather, it is a composite ofthe opinions of practicing engineers, construction experts and the DFI SlurryWall/Trench Committee. This publication is intended to provide an under-standing of standard slurry wall practices in the U.S. heavy construction indus-try.

Industry practice standards and DFI practice guidelines are intended to high-light major considerations in selecting structural slurry wall elements for tem-porary and permanent use as foundation elements. Since the application ofslurry wall elements in tunnels, bridges, buildings, dams, marine construction,etc. is so diverse, a single publication cannot cover all the conditions andcodes governing its specifications and usage. It remains the primary respon-sibility of experienced professionals to provide the appropriate contract docu-ments and use their own judgment in each instance.

The Committee does not anticipate that this publication will cover every proj-ect circumstance nor will it replace the importance of local experience. Thereare numerous factors that need to be considered on a project-by-project basisby experienced engineering and construction personnel. Among them are theactual design parameters, site conditions, subsurface characteristics, ground-water conditions, structure water tightness, site accessibility, available equip-ment, desired work practices, etc. These factors are discussed and guidelinesare provided in this document.

The history of slurry wall construction will provide some insight into the devel-opment of the process used in the United States and worldwide. The namesof many individuals and corporations who contributed to the development ofslurry wall construction have been omitted from this publication in the interestof brevity. Information obtained from references is cited in the references inPart V by [reference number]. Figures referenced in the text material areincluded in Part IV. Additional resource literature is listed in the bibliographyin Part V. English customary units of measurement are used through this pub-lication; metric conversions in scientific units (SI) and customary kilogramunits are listed in Part IV. Users of this publication are encouraged to contactDFI with questions and comments.

This and other DFI publications are available from:The Deep Foundations Institute

326 Lafayette AvenueHawthorne, NJ 07506

Tel: (973) 423-4030Fax: (973 423-4031

Email: dfihq@dfi.org

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DEEP FOUNDATIONS INSTITUTESLURRY WALL/TRENCH COMMITTEE MEMBERS

Chairman

Poletto, Raymond J., P.E. Mueser Rutledge Consulting Engineers

Members

Bonita, John Ph.D, P.E. Weidlinger Associates, Inc.

Bruce, Donald A. Ph. D, P.E. Geosystems, L.P.

Cardoza, Edmund J. Jr., Private Consultant

D’Argenzio, Domenic, P.E. Mueser Rutledge Consulting Engineers

Hosseini, Mamoud, P.E. Clark Construction Company

Jacobsen, Edward, P.E. Case Foundation Company

Lager, David E. NETCO Inc.

Nicholson, Peter J., P.E. Nicholson Consulting Company

Paniagua Z., Walter I. Pilotec Cimentaciones Profundas

Ressi di Cervia, Arturo, L., Ph.D Treviicos Corporation

Schmednecht, Fred C. Slurry Systems Inc.

Schranz, Gernot Liebherr Werk Nenzing Gesmbh

Tamaro, George J., P.E. Mueser Rutledge Consulting Engineers

Former Contributing Committee Member

Pearlman, Seth, L., P.E. DGI-Menard, Inc.

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NOMENCLATURE USED IN SLURRY WALL CONSTRUCTION

Illustration 1: Standard Terms

RELATED TERMS AND CONSTRUCTION METHODS

The term “Slurry Wall” is commonly used in the United States and refers to theconstruction of concrete elements using a slurry fluid to support the sidewallsof the excavation before the slurry is replaced with tremie concrete and otherstructural elements. The terms “Diaphragm Wall” and “Milan Wall” are usedelsewhere and refer to the final constructed foundation element. Cutoff Wallsand Slurry Trenches are constructed similarly to structural slurry walls using avariety of backfill materials, but their purpose is to provide either a water cut-off, environmental barrier or collection system related to groundwater controlor environmental mitigation and are not the subject of this publication.

DEFINITION OF A SLURRY WALL AND OTHER STANDARD TERMINOLOGY (See Illustration 1)

A “Slurry Wall” is a structural foundation element constructed below groundusing a controlled slurry fluid, consisting of a colloidal suspension of eitherbentonite, pulverized clays or polymer thoroughly mixed with water, to supportthe side walls of an excavation, that is later backfilled with tremie concrete,which may be reinforced with a steel cage, steel tendons or wires, steelbeams or a precast panel. In practice, the controlled slurry fluid level in thetrench is kept near the ground surface and several feet above the groundwater level. A guide wall is placed on each side of the wall alignment to pro-

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vide vertical and horizontal alignment control for the excavation and subse-quent support of the tremie equipment and reinforcing elements to be placedin the excavated unit. The slurry wall is constructed in discrete units, called“panels,” which are usually joined at their ends formed by keyed joints from anextracted end stop shape, or can be prepared by milling along a vertical planeat the cast end of the panel. Steel beams are often used as joints or connec-tors between panels. Panel dimensions in plan commonly range between 2 ft.and 5 ft. in width and between 7 ft. and 25 ft. in length. Panels are excavat-ed in one or more passes with overlapping of excavating buckets or drillingmachines depending on soil/rock conditions and the geometry of the slurrywall system. Additional definitions of standard slurry wall construction andequipment terms are provided in Part III.

HISTORY OF SLURRY WALL CONSTRUCTION

The origin of the use of colloidal clay slurries to stabilize the sidewalls and bot-tom of an excavated trench may be traced to the earliest known methods ofsinking deep wells by the Chinese in the Third Century B.C. They learned thatthe efficiency of their tools in rock was improved by the addition of water; for-mations were softened and cuttings were more easily removed with bailingtools.

This practice of pouring water into drilled holes continued through the middleof the Nineteenth Century when fluid flushing and rotary drilling systems weredeveloped in France. By the end of the century, the sealing and stabilizingcharacteristics of clay and water slurry were identified and put to use in thedeveloping oil industry in the United States.

In the first thirty years of the Twentieth Century, the properties of drilling fluidsbecame more and more important as well depths exceeded one mile.Between 1926 and 1929, bentonite was first used as a suspending and gellingagent for drilling muds.

The use of slurry to support the sidewalls and bottom of excavated trenchesfollowed directly from bored pile experience in Europe. Early applications withslurry walls experimented by using various concrete and plastic concretematerials to form barriers, called cutoffs, to seal water infiltration through var-ious soil layers. The interlocking of bored piles to form continuous walls (1930through 1950, in Italy and France) marked the next logical step in the devel-opment of slurry wall technology [1].

By 1950, Italian contractors developed methods of excavating elongated pan-els using percussion drilling equipment and a stabilizing slurry. The techniquewas patented and the first cutoff walls were installed at the Santa Maria Damnear Venafro, Italy.

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During the next decades, primarily Italian and French construction firms andmanufacturers developed a variety of equipment for the installation of slurrywalls, using the “joined panel” technique. The equipment developed for slurrywalls included: mechanical cable-activated and Kelly-guided clamshell buck-ets, hydraulic activated clamshells, reverse circulation methods with drillingtools, percussion chisels, churn drills, bentonite slurry mixing and cleaningunits, tremie concreting equipment, jointing systems and devices for monitor-ing the effectiveness of the technique. Developments in Italy and Francequickly spread to the East and West in the form of license agreements andexportation of equipment and expertise. Today, contractors continue to evolvethe techniques of the industry and modern hydraulic milling or “hydromill”excavators are the current behemoths (monster machines) used in slurry wallconstruction.

The continuous trenching method of slurry cutoff wall construction developedin the United States in parallel with the European panel wall approach. In themid 1940’s, chain-bucket dredgers and dragline machines were busy alongthe Mississippi River and on the West Coast excavating long, continuous,slurry supported trenches, which were backfilled with clay to form cutoff wallsto protect adjacent land and structures from inundation. The improvements inexcavating equipment (deep digging hydraulic excavators) and backfill mixdesign (well graded materials with a significant fraction of plastic fine grainedsoils) during the last five decades, have lead to the use of the soil backfilled,continuously excavated slurry trenches, as the most technically effective andmost cost efficient method of seepage control and waste containment in theUnited States.

Slurry wall panel type construction is utilized all over the world in constructionof large underground structures. The most dramatic applications and severetests of the method have been on dam rehabilitation projects in NorthAmerica, where panel walls were carried to depths in excess of 400 feet to astricter tolerance than previous construction practice had achieved. The suc-cess of these projects must be attributed to the ingenuity of engineers, con-tractors, equipment manufacturers and slurry experts of today and yesterday.

The first structural slurry wall construction was used in the United States in1962 on a tunnel project located in Brooklyn, New York City, for a 25 ft. diam-eter access shaft beneath the East River [2]. It was constructed to a depth ofalmost 80 ft. (See Photo 1).

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Photo 1: First U. S. Structural Slurry Wall project in Brooklyn, NY.Used Rotary Reverse Circulation Drill to form circular panels.

Shortly thereafter, several building and subway projects in Boston and SanFrancisco used the slurry wall method to construct foundations for these struc-tures. After these projects started, a slurry wall was constructed in 1966-1968on a monumental scale ($10 million) for the basement retaining walls of theWorld Trade Center (See Photo 2). Following these trail blazing projects, over280 additional slurry wall projects have been completed in the United States.A total of more than 18 million square feet of structural slurry wall has beeninstalled in the U.S. during the last four decades. The largest single use ofslurry wall construction on a single U.S. project is the Central Artery TunnelProject in Boston for the Massachusetts Turnpike Authority from 1993 to 2004(See Photo 3). More than 6 miles or 2,900,000 square feet of structural slur-ry wall panels have been constructed on this project, costing more than onethird of a billion U.S. dollars.

Photo 2: World Trade Center’s slurry wall and excavation phase in 1969.

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Courtesy of Rodio

Courtesy of G. Tamaro, Mueser Rutledge Consulting Engineers

Information has been gathered on 361 completed projects in the UnitedStates, Canada, Caribbean areas and Mexico. These projects are catalogedin Part VI, Project List. These projects are alphabetically listed by the abovelocations. Many slurry wall projects are concentrated in the District ofColumbia, Boston and New York City and are grouped together. Some proj-ects (e.g. subway sections) are similar in nature and are also combined into asingle group. Six types of project information (slurry wall thickness and depth,type of wall and excavation support, project size, description and year con-structed) are included as the basic data in the summary of structural slurrywall applications.

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Photo3: Bauer low-headroom hydromill workingon Boston’s Central Artery Tunnel Project.

Courtesy of Big Dig, Central Artery Tunnel Project

viii

TABLE OF CONTENTSPage

Preface.........................................................................................................i

DFI Slurry Wall/Trench Committee Members .............................................ii

Nomenclature Used in Slurry Wall Construction ........................................iii

Related Terms and Construction Methods .................................................iii

Definition of a Slurry Wall and other Standard Terminology ......................iii

History of Slurry Wall Construction ............................................................iv

Tables of Contents....................................................................................viii

PART I INDUSTRY PRACTICE STANDARDS

1. Classification of Slurry Wall Panels......................................................1

2. Typical Sizes of Slurry Wall Panels ......................................................5

3. Panel Depths ........................................................................................6

4. Equipment.............................................................................................6

5. Slurry Fluids........................................................................................16

6. Phases of Panel Construction ............................................................18

7. Inspection, Records and Final Condition Observations ....................18

Figures referenced in Part I and Part II are shown in Part IV.

TABLE OF CONTENTS (continued)

Page

PART II DFI PRACTICE GUIDELINES

1. Scope ...............................................................................................21

2. Contractor Qualifications ..................................................................21

3. Subsurface Investigation ..................................................................21

4. Design and Site Considerations.......................................................23

5. Materials ...........................................................................................25

6. Slurry Fluids .....................................................................................27

7. General Submittal Requirements .....................................................27

8. Preparation for Excavation...............................................................28

9. Excavation........................................................................................29

10. Reinforcement Placement ................................................................31

11. Concrete Placement .........................................................................32

12. Tolerances ........................................................................................34

13. Differing Site Conditions ...................................................................34

14. Completion of the Work....................................................................35

15. Water Tightness Criteria ...................................................................35

16. Compensation ..................................................................................37

PART III DEFINITIONS ...................................................................38-48

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TABLE OF CONTENTS (continued)

Page

PART IV FIGURES ..............................................................................49

Figure 1 - Classification of Panels .....................................................50

Figure 2 - Slurry Wall Panel Configurations.......................................51

Figure 3 - Types of Panel Joints ........................................................52

Figure 4 - Types of Clamshell Buckets ..............................................53

Figure 5 - Slurry Excavation Operations ............................................54

Figure 6 - Cleanup with Sand Separating Unit ..................................55

Figure 7 - Phases of Slurry Wall Construction ...................................56

Figure 8 - Slurry Wall Inspection Report Form...................................57

Figure 9 - Slurry Fluid Test Report Form ...........................................58

Figure 10 - Tremie Concrete Inspection Report Form .......................59

Figure 11 - Major Types of Slurry Wall Construction and Applications...............................................................60

Figure 12- Typical Guide Wall Construction.......................................61

Figure 13- Guide Wall Constructed in a Prepared Trench.................62

Figure 14- Slurry Wall Tolerances ......................................................63

PART V ADDITIONAL INFORMATION

References................................................................................................64

Bibliography ..............................................................................................65

Metric Conversion Table ...........................................................................69

PART VI PROJECT LIST

Slurry Wall List Parameters ......................................................................70

Slurry Wall Projects in North America .................................................71-92

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PART I INDUSTRY PRACTICE STANDARDS

1. CLASSIFICATION OF SLURRY WALL PANELS

There are many ways to classify structural slurry wall elements, but the DFIcommittee chooses to limit these descriptions to three functional require-ments, namely: design function, plan configuration and type of panel rein-forcement. (See Figure 1 in Part IV for panel classification).

Slurry walls can function as:

1. Curvilinear or linear elements for temporary and/or permanent structuresto resist lateral forces transferred from the ground, water, earthquakesand various surcharge loads.

2. Load bearing elements in various plan shapes to resist vertical forces.3. Combination Elements to resist combined forces under conditions 1

and/or 2. For example, elliptical shafts with various openings for tunnelsand conduits have been commonly used for deep excavations.

Slurry walls can be constructed in any plan configuration, solely limited by thedimensions of the excavation equipment, the type of geology and the practi-cal imagination of the engineer and contractor (See Figure 2 in Part IV).

Slurry walls can be reinforced by the addition of the following structural ele-ments:

1. Reinforcing steel bars or fiber reinforcing - (Conventional Concrete Panel).2. Structural steel beams - (Soldier Pile and Tremie Concrete Panel).3. Prestressing steel elements - (Precast Concrete Panel). 4. Tensioned steel prestressing bars, wire strand or wire elements - (Post-

tensioned Concrete Panel).

All structural slurry walls use structural concrete comprised of Portlandcement, occasionally fly ash, fine and coarse aggregates, water and concreteadditives that is usually specified in the range of 3000 psi to 5000 psi com-pressive strength at 28 days.

Slurry wall panels with various reinforcements are illustrated in Figure 1 inPart IV and are commonly used in United States construction practice. In aconventional panel, an end stop shape is usually placed to form the jointbetween adjacent panels. In some cases, joints can be cut at the end of thepanel by using a rotary grinding or milling tool (hydromill). An unreinforcedconcrete panel with formed joints was originally used for water cut-off wallsand sometimes without joints for load bearing elements. Circular shafts andelliptical shaped cofferdams are examples of slurry wall applications that haveachieved excellent results when properly designed and have allowed the con-struction of structures without bracing or obstructing any of the work during the

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excavation of areas, to 250 feet in diameter and 80 feet in depth. Other slur-ry wall systems may use different types of joints, which are described, in latersections depending on their special applications in deep foundations.

When used as part of an earth support system or permanent foundation wall,a reinforced panel resists the bending moments and shears caused by verti-cal and lateral loads and is supported by steel, concrete or timber bracing, soilor rock tiebacks or anchors and/or the floor systems of a structure. A rein-forced panel can include a variety of inserts, such as: plates, keys, dowels orsleeves attached to the reinforcing cage and is often used as the permanentfoundation wall for buildings and underground structures (See Photo 4).

Another type of reinforced panel is aSoldier Pile and Tremie Concrete Panel,called “SPTC” panel. This type of panelhas special applications in “open cut”and “cut and cover” construction wherenarrow, long and deep excavations aretemporarily supported laterally with pipeor beam struts. The “cut and cover”SPTC wall was installed in SanFrancisco in 1967 for the construction ofthe Powell St. subway station of theBART transit system. This panel wallcan be constructed by two alternativemethods: pre-drilling and setting beams

(soldier piles) at 6 to 8 foot spacing in advance of the panel excavation or set-ting beams within an excavated, slurry filled trench. The steel beams can actas vertical reinforcing and panel joints. Concrete is tremied between thebeams to form a watertight wall system depending on the quality of the panelinstallation. If large beam spacing is used, then a reinforcing cage is installedbetween the beams to serve as “concrete lagging”.

Counterfort and corner panels are special T-shaped and L-shaped panelsused for retaining walls and corners of walls. The counterfort panel is highlyadapted to serve as a cantilever wall without bracing or as a thin wall with lightreinforcing that can span large distances with a minimum number of lateralsupports. Both of these types of conventional concrete panels are construct-ed as a monolithic tremie concrete pour with a single cage to accommodatethe plan layout of the walls.

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Photo 4: Reinforcing cage with tiebacksleeves and floor keys for conventional panelconstruction in Washington DC.

Courtesy of The Architect of U.S. Capitol

Precast concrete panels are used where afinished wall with a uniform or architecturaltextured face is desired. A precast panel isinserted into an oversized trench containinga cement-bentonite (C-B) slurry (See Photo5). The C-B grout sets shortly after the panelis aligned vertically and horizontally. In theprecast concrete panel system, a verticalrubber waterstop, usually a patented sys-tem, and C-B grout are installed within thepanel joint. These materials seal the paneljoints and form a watertight system.Sometimes, an excavation for a precastpanel is made under bentonite slurry. A pre-cast panel is then suspended within theexcavated panel and the panel is grouted atthe bottom to serve as the bearing supportfor the panel and as replacement of some ofthe slurry. Later, the space between thetrench sidewalls and the concrete may bebackfilled with cement bentonite or otherself-hardening cementitious materials.

Precast concrete panels were initially used in France in the early 1970’s, andare less commonly used in the United States, except where appropriatelyskilled labor and large pre-casting facilities are available. The disadvantage ofthis system is the inherent difficulty of installing sequential panels in urbansites, especially where utilities cross the wall alignment. In these cases, theexcavation is stopped and the utilities are relocated before the next panelexcavation can resume. It is difficult to install a precast panel element perfect-ly within the gap left to allow for a later utility relocation, and as a result thewatertight joint connection between panels may be compromised.

Patented post-tensioned panel systems were developed during the 1970’s inItaly and Great Britain. A post-tensioned panel is constructed in the samemanner as a conventional reinforced concrete panel. However, draped post-tensioning tendon ducts are substituted for heavier reinforcing bars (SeePhoto 6).

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Photo 5: Precast wall panel installa-tion on railroad construction inMassachusetts.

Courtesy of TREVIICOS Corp.

The strands are pulled within the ten-don ducts after the concrete sets andthen the steel wire strands are post-tensioned and grouted. This systemreduces the quantities of concrete andsteel needed and permits relativelylarge distances between brace levels,thereby minimizing the number ofbraces. Post-tensioned panels havestructural bending resistance equiva-lent to counterfort (T-shaped) panels.This type of panel is difficult to utilizewith multiple brace and floor levelsbecause tendons can best be placedfor only one or two levels of support.

Load Bearing Elements are usuallyreinforced with structural elementswithin the panels in various planimetricshapes. Round, single or multiplebucket excavations can be used to cre-ate I, T, X, H, L, C or Y panel shapes(See Figure 2 in Part IV). Their primaryfunction is to support large vertical loads and other applied forces [3].Structural beams and/or other structural elements can be installed within thepanel to connect to the structural framing system, particularly where top-downor up-down construction methods are used in a project. This type of panel canbe easily integrated into a monolithic structure by doweling into subsequentconstruction. Concrete columns or mat foundations can be directly cast ontothe load-bearing element after unsuitable concrete is removed from the top ofthe element. A load bearing element obtains its load capacity from either directend bearing on the underlying soil strata and bedrock, through friction/adhe-sion along the embedded depth of the element or through a combination ofend bearing and friction/adhesion.

Joints between panels are illustrated in Figure 3 in Part IV. The early practicewith conventional panels was to use pipes to form round joints or “end stop”panel joints. Later, structural beams were used in the United States withSoldier Beam and Concrete Lagging Panels. Finally, welded structural steelshapes and built-up members are also used as panel joints, and are easier toremove by using either the crane’s lifting line or by the closing and opening ofa collar extraction device operated by a hydraulic power unit after tremie con-crete is placed in the panel. The optional waterstop within a panel joint hasbeen rarely used in United States practice because of difficulty in execution.The construction practice of installing waterstops within panel joints is usual-ly more costly than sealing joints with grout materials.

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Photo 6: Reinforcing cage with post-tensioned strands for panel in BostonCentral Artery project.

Courtesy of TREVIICOS Corp.

2. TYPICAL SIZES OF SLURRY WALL PANELS

Panel dimensions and configurations are usually controlled by the technicalelements of the design and the size of the equipment that is available to thecontractor performing the work. It is obvious that the panel thickness andlength can be no thinner or shorter than the width and the length of the exca-vation bucket. Short panel lengths, usually in the range of 6 to 7 feet, shouldbe used at areas of unstable soils or where very high surcharge loads resultfrom adjacant structures. Longer panels, ranging to 30 feet in length, can beused in stable soils and favorable site conditions. Panel lengths can vary any-where from 6 feet to 30 feet; however, many panel sizes are dictated by thelocation of internal bracing, tieback spacing, interior column layout and loca-tions of adjacent footings.

Walls are commonly 24, 30, 32, 36 and 48 inches (2.0, 2.5, 2.67, 3.0 and 4.0feet) thick. Thicker walls are available if required for bending and shear resist-ance or if required to support high vertical loads. Thinner walls are sometimesused for special conditions, which is discussed in Section 4 of Part I. Typicalslurry wall panel dimensions and other conditions affecting their selection areindicated in Table 1.

TABLE 1 - TYPICAL SLURRY WALL PANEL DIMENSIONS

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PanelWidth or WallThickness(Note 1)

Panel Length

Size limitations are dictated by commercially available equipment and site geologicalconditions; ground stability, water levels, and proximity to adjacent structures. Consult anexperienced specialty contractor and geotechnical engineer for their recommendations.

Conventional Soldier Counter- Corner, Precast Post- LoadConcrete Pile & fort, L-Panel Concrete tensioned BearingPanels Lagging T-Panel Panel Panel Element

18”-21” Note 2 Note 2 Note 2 Note 2 6’ to 8’ Note 2 Note 2

24” 7’ to 25’ 6’ to 10’ 10’ x 10’ 14’ to 25’ 6’ to 8’ 12’ to 20’ 7’ to 25’

30” 7’ to 25’ 6’ to 10’ 12’ x 12’ 14’ to 25’ 6’ 12 to 20’ 7’ to 25’

32” 7’ to 25’ 6’ to 10’ 12’ x 12’ 14’ to 25’ 6’ 12’ to 20’ 7’ to 25’

36” 7’ to 20’ 6’ to 10’ 12’ x 12’ 14’ to 25’ 6’ 12’ to 20’ 7’ to 25’

40” 7’ to 20’ 6’ to 10’ 12’ x 12’ 14’ to 20’ Note 3 Note 2 7’ to 20’

48” 7’ to 16’ Note 4 Note 2 14’ to 16’ Note 3 Note 2 7’ to 20’

60” 7’ to 12’ Note 4 Note 2 14’ to 16’ Note 3 Note 2 7’ to 16’

Table 1 Notes:

1. Panels of 12” to 14” thickness have been constructed outside the U.S.with special hydraulically operated clamshell rigs.

2. Only used under special conditions.3. Length and width of precast panels are dictated by shipping and handling

limitations.4. Special built-up member sizes are required for walls that are more than

40” thick.

3. PANEL DEPTHS

A. For Excavation in Relatively Uniform Types of Soil.

1. By conventional light duty, cable-hung clamshell bucket, telescop-ing Kelly-mounted bucket or drilling machine, depths of approxi-mately 100 ft. can be excavated. Special telescoping Kelly-barsmay reach depths of 165 ft. [4]. Panel depths may reach 300 ft.using cable-hung, heavy duty clamshell buckets.

2. The industry standard for out of plumbness tolerance is one per-cent of the depth of the panel excavation. For panel depths inexcess of 100 ft. verticality control is critical for connecting endsof adjacent panels and tighter tolerances may be required.

B. For Excavation in Layered Soils Mixed with Cobbles, Boulders andRock.

1. Panel depths are generally limited to less than 100 ft. using light-duty clamshell buckets and percussion, auger or star drills intogranular soils or soft rock.

2. Panel depths are generally limited to less than 150 ft. usingheavy-duty clamshell and rotary or percussion drilling equipmentin medium to hard rock.

3. Panel depths are generally limited to 300 ft. for excavation anddrilling with special equipment and excavating with heavy dutyclamshell buckets and chisels.

4. Panel depths as reported by manufacturers’ literature could beconstructed to 500 ft using hydromills. However, the operation ofthis equipment in very dense soils or hard rock can limit the paneldepths because the vertical alignment and the twist must be con-trolled to properly connect the adjacent panels.

4. EQUIPMENT

A. Panel Excavation

For the past 50 years, the main excavation tools have been cable-sus-pended (wire-rope) or Kelly- guided clamshell buckets and percussionchisels. Either crawler cranes or specialty tripod controls clamshell buck-ets or quadruped rigs with a winch system. Commonly used in the indus-try are several styles of mechanical, cable-hung clamshell buckets andtheir physical characteristics are shown in Table 2. Tripod rigs were orig-inally used in some projects where limited space was available for exca-vation equipment. Rotary drilling techniques were developed in the1950’s through the 1970’s and used in Japan and Europe throughout thisperiod.

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TABLE 2 - CHARACTERISTICS OF MECHANICAL (WIRE-ROPE) CLAMSHELL BUCKETS

Nominal Bucket Width Bucket Bite Bucket Bucketor Wall Thickness Lengths Height with Weight

Closed Jaws

(inches) (ft) (ft) (ft) (tons)

18-21 1.7 6.0 to 9.2 12.3 to 13.5 8 – 10

24 2.0 7.0 to 13.8 13.8 to 14.7 10 – 13

30 2.5 7.8 to 13.8 20.5 to 23.9 11 – 14

32 2.7 7.8 to 11.3 20.5 to 23.9 12 – 15

36 3.0 7.8 to 13.3 20.5 to 21.5 13 – 16

40 3.3 10.0 to 11.3 21.0 to 22.9 14 - 19

48 4.0 10.0 to 14.0 23.0 to 25.6 15 – 22

60 5.0 10.5 to 14.0 24.0 to 26.0 19 – 28

Table 2 Notes:

1. Typical sizes available from manufacturers and specialty contractors.2. Mechanical buckets are generally heavier and have a smaller bite and

height than hydraulic buckets.3. Buckets are available with curved or rectangular jaws.4. Special bucket sizes can be fabricated for special projects and low

headroom. (Consult manufacturers and specialty contractors.)

1. Clamshell Buckets

The first slurry wall clamshell buckets were free-hanging, two cable buck-ets operated by two drum winches on tripod rigs or a crane. Buckets areusually controlled by a crane operator and may have either round jaws orrectangular jaws. Excavation with round end buckets facilitates the place-ment of conventional stop end pipe joints. Rectangular jaws are moreappropriate when flat stop end joints or beams are used to form the endsof panels (see Figures 3 and 4 in Part IV). The jaws can be fitted with dif-ferent teeth as needed. Most buckets work with 3 teeth on one side and2 on the other for up to 40 inch thick walls; 4 teeth on one side and 3 onthe other are used for thicker walls.

For a free-hanging excavation bucket, a guiding system is needed to min-imize the rotation caused by the lifting and closing cables of the bucket.To ensure a vertical excavation, the bucket is equipped with a top guidethat is of the same width as the jaws (see Photo 7). The guide also assistsin maintaining vertical alignment and adds weight, which improves the

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bucket capability to penetrate denser soils. Operator skill has an impor-tant role in the control of the mechanical clamshell bucket and keeping itvertical during excavation. Swinging the bucket 180 degrees on the cableregularly during excavation helps to minimize the twist or corkscrew devi-ations frequently encountered in penetrating denser soils or weatheredrock.

Clamshell buckets can be manipulated by adjusting the crane’s liftingcables with one left twist and one right twist to avoid the bucket to drift toone side. The bucket may be turned at the side of the trench after eachcycle of excavation. Modern winches in crawler cranes allow the opera-tor to rotate the bucket smoothly around the vertical axis. This operationalso improves the verticality of the wall.

Excavating buckets can also beattached to a Kelly-bar (SeeFigures 4 and 5 in Part IV).The Kelly can be tubular, tele-scopic, or a large beam. Themechanism is operated from astandard crawler crane bymeans of a specially designedattachment consisting of aKelly-bar and a Kelly-guide.The use of the Kelly-barensures control for the insertionand removal of the bucketbetween and away from theguide walls, thus increasing the

productivity in the excavationcycle. In addition, the weight of

the Kelly helps the excavating bucket penetrate into the soil. One of thedrawbacks of the Kelly equipment is that for difficult soil conditions, it isnecessary to also use percussion tools to remove cobbles or bouldersand/or to remove weak rock. In those conditions another excavating rigis usually provided to employ percussion tools.

A Kelly-guided or a free-hanging bucket can also be hydraulically operat-ed. This type of bucket has jaws which can be opened and closed eitherby two hydraulic cylinders, one to each jaw, (see Photo 8), or by a single,larger hydraulic cylinder operating both jaws. The hydraulic lines areautomatically synchronized with single or dual spoil feeds on the Kelly and

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Photo 7: Mechanical clamshell bucket.

Courtesy of Liebherr Nenzing Gesmbh

powered by the crane’s power or auxiliary hydraulic power pack.In the last couple of years clamshell bucket sizes have increased inweight and size. Bucket widths of 48 inches, weighing about 28 tonsempty and 36 feet high, are in current use in Europe for better productionand better verticality. These buckets have interchangeable sets of jawsand an upper bucket body to suit the range of needed panel widths. UnlikeU.S. practice, some European contractors elected to not use guide walls,but rely on the crane’s controls having gyroscopes and inclinometers toguide the clamshell equipment and to indicate the depth of excavation andthe twist of the bucket.

Special buckets and crane rigs working up to 16 feet high clearance andtight quarters have been adapted for specific job conditions and panelconfigurations (See Photo 9). Three-jawed buckets have been used forconstructing T-shaped panels. Buckets can have side cutters added toincrease the panel thickness if needed for special conditions. The cost ofthis modification is usually greater than the cost of using the next avail-able size bucket. Buckets and rigs need to be modified where excavationis limited in low-head room conditions, generally less than 20 feet.

Slurry wall buckets are usually fabricated mechanically simple for mainte-nance and adequately strong to stand up to adverse digging conditions.Some manufacturers install special seals on bucket sheaves to providelubrication for long term usage. Buckets need to be of sturdy constructionin order to be able to act as an opened jaw chisel in dense soil. Bucketsare commonly equipped with different types of teeth to facilitate digging invariable soil conditions that may contain cobbles, boulders, and widelyvarying depths and quality and conditions of rock. The industry opinion isthat clamshell buckets provide more flexibility and adapt more easily foroperating in difficult soil conditions than drilling machines. The standardtolerance for verticality can be improved to 0.5% with special clamshell

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Photo 8: Kelly-bar guidedclamshell bucket used inWashington DC.

Courtesy of Nicholson Construction Corp.

bucket handling techniques. This improvement will affect operations byslowing down the excavation rate for soil containing cobbles and boul-ders.

2. Percussion Equipment

When the material to be excavated contains cobbles or boulders or isbedrock, the panel excavation is advanced using percussion tools. Beamsections or multiple steel plates can be welded together (four to six star-shaped chisel) and hardened at the tip to serve as a heavy percussiontool (see Photo 10). The chisel can vary from 10 feet to 25 feet long andweigh 5 tons to 15 tons. The chisel is raised and dropped by a cable ona crane or by a percussion type rig. When panels are socketed into hardrock, a percussion rig with a reverse circulation system is usuallyemployed to pulverize and remove rock material.

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Photo 9: Mini-excavator rigworking on building site inMexico City

Photo 10: Percussion chiselwith 6 hardened bits for

rock excavation.

Courtesy of Pilotec Cimentaciones Profundas

Courtesy of Mueser Rutledge Consulting Engineers

3. Drilling and Milling Machines

Rock can also be removed using a rig with multiple rotating drill heads orroller bits, and reverse circulation of slurry. The reverse circulationmethod is used to lift slurry through the hollow drill stem, removing soiland cuttings to a disposal location. Direct suction or an airlift can be usedto lift the slurry and pulverized materials at the bottom of the drill head.The soil cuttings and the slurry are separated over a vibrating screenand/or desanding unit. The drilling fluid is returned to the panel throughthe rig’s supply line or discharged directly to the trench. An early rotarydrilling machine with reverse circulation is shown in Photo 1 in the intro-duction section on page vi.

In the early 1950’s, European contractors used drilling machines when thelight clamshell buckets available could not remove the soil or when theexcavation had to be carried to depths considerably greater than 100 ft.As larger crawler cranes and buckets became available in the 1960’s, thereverse circulation drilling method became less economical to utilize onordinary slurry wall projects, except for dams where vertical alignment anddrift of slurry wall elements had to be controlled within strict tolerances.

An improvement to this method occurred in Japan in the 1970’s when aspecial multiple head drilling technique was developed. The rig used sub-mersible drills suspended by a cable rig traveling on a rail system. Themultiple drill bits had a suction pump to continuously remove the cuttings.One of the disadvantages of this system of excavation was the inability toremove large cobbles, boulders or rock fragments through the 6-inchdiameter suction hoses.

In the 1970’s and 1980’s, European equipment manufacturers and con-tractors improved the reverse circulation drilling method by manufacturingtrench cutter (hydromill) machines. See typical hydromill tool and rig inIllustration 2. It is possible to excavate trenches for slurry walls with ahydromill at a greater rate than with clamshell bucket rigs, but usually avertical excavation down to 30 to 50 ft is needed to operate the intakepump at the bottom of the cutters.

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The general characteristics of commonly used hydromills are given inTable 3 below. A crawler crane supports and controls this equipmentwhich consists of a steel frame with a dredge-type mud pump and twohydraulic drives and cutter wheels mounted on a horizontal axis attachedto its base frame (See Illustration 2 and Photo 11). The drives rotate thedual wheels in opposite directions. The cutter wheels, commonlyequipped with tungsten carbon tipped teeth, continuously loosen andbreak up soil and rock material and mix it with slurry. Removable cuttingteeth, button-type or wedge-type, are usually welded on multiple fins thatare diagonally mounted on the wheels. These teeth are capable of cuttingsoft to medium rock up to 10,000 to 15,000 psi compression strength.The cost of replacing carbide or diamond bit teeth and equipment down-time are usually considered in contractor’s costs and selection of eithervertical rotary or hydromill drilling machines.

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Illustration 2: Model FD 32 Casagrande Hydromill [5]. See Table 3 for labeled dimensions.

Table 3 - Characteristics of Hydromills [5]

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Bauer Series BC 2.0 to 6.0 9.2, 10.5 30 to 52 27 to 55 0 to 25 5 to 11 215

Bauer MBC 30 2.0 to 5.0 9.2 16.4 20 to 25 0 to 30 7 175

Bauer CBC 33 2.0 to 6.0 9.2 33 to 55 22 to 38 0 to 30 7 330

Casagrande K2 2.0 to 3.3 8.2 40 19 0 to 27 10 330

Casagrande K3L 2.0 to 4.0 10.3 47 32 0 to 31 10 400 to 500

Casagrande K3Clow headroom 2.2 to 4.0 10.3 40 19 0 to 31 10 230

Casagrande FD 25 2.0 to 3.3 8.2 32 19 to 30 0. to 27 7 165

Casagrande FD 32 3.0 to 6.0 10.5 50 44 0 to 19 11 200

Soletanche Hydrofraise HF 4000 2.0 to 4.7 9.2 50 25 - 10 400 to 500

Soletanche HydrofraiseHF 12000 4.7 9.2 50 60 - 10 400 to 500

Soletanche HydrofraiseHFA-4RCII 2.5 to 4.0 9.2 40 18 - - 300

Rodio Urbanalow headroom 2.0 to 4.0 7.9, 9.2 20 20 - - 115

Rodio Latinalow headroom 2.0 to 4.0 7.9, 9.2 16.4 20 - - 145

Cutter Cutter Discharge Max. Manufacturer Width Length Tool Height Cutter Cutter Disk Pumping Excavation

Model No. “a” “l” “hd” Weight Speed Rate Depth(ft) (lf) (lf) (tons) (rpm) (yd3/min.) (ft)

The soil and rock cuttings are pumped through the rig’s discharge hose toa slurry treatment plant for separation and return of clean slurry to thepanel. See Illustration 3 for the typical schematic diagram of the opera-tion of a hydromill system. During the hydromill excavation process, thespoil-laden slurry can be pumped usually up to 1500 ft to the plant. Thisdistance can be increased with the addition of in-line booster pumps. Ahigh capacity plant can treat 500 to 1500 yd3 per hour of slurry and sepa-rate solids through a series of vibratory screens and cyclones down to acoarse silt size. Fines can be further removed from the slurry with specialcentrifuges in a separate cycle. Slurry storage tanks at the treatmentplant need to have at least twice the volume of the panels to be excavat-ed.

Guidance systems attached to the hydromill machine permit modeststeering of the cutters. The verticality of hydromill excavation is monitoredwith special inclinometers mounted on the cutter frame and connected toa readout device and recorder inside the crane operator’s cab. The oper-ator can make adjustments to correct lateral drift and longitudinal plandeviations by varying the relative speed of the cutters and moving theinterior shield connected to each side of the main frame of the cutterassembly. Hydromill machines are usually capable of achieving a verticaltolerance in the range of 0.2% to 0.5% in the longitudinal and lateral direc-tion in most soil conditions without cobbles and boulders. The opinion ofthe industry is that soils mixed with cobbles and boulders are the most dif-ficult to excavate with the hydromill equipment and require more stringentverticality control to achieve design tolerances. This tolerance is more dif-ficult to achieve when variable weathered rock or rock with closely jointedor fractured zones are encountered.

Hydromill equipment is also fabricated for working in 16 feet or less head-room conditions as seen in Photo 3 on page vii and Photo 12. For limitingdisruption to traffic and area occupants, the desander, slurry treatmentand slurry mixing operations can be set-up fairly distant from the excava-tion of the panel.

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Illustration 3: Hydromill Operations

B. Slurry Mixing and Desanding

1. Proper mixing of bentonite is needed to produce effective dispersionand uniformity of the bentonite. Colloidal mixers produce the bestpossible mixing. Sometimes flash mixers are used. Careful controland testing of the bentonite slurry must be maintained throughout theduration of the panel excavation and prior to concrete operations.Sprinkling or pouring dry bentonite into the trench and relying on theexcavation tool to mix the bentonite will result in lumpy slurry with vari-able viscosity and filtration properties usually falling outside of desiredlimits.

2. Bentonite slurries are circulated through a desanding or de-siltingdevice prior to the placement of concrete in the panel and/or prior tostorage or re-use. Used bentonite slurry is pumped onto a vibrating

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Photo 11: Hydromill (trench cutter) forconstruction of slurry walls.

Photo 12: Low headroom hydromilltrench cutter working Boston.

Courtesy of Big Dig, Central Artery Tunnel Project

Courtesy of TREVIICOS Corp.

screen sand separator unit that allows the screened slurry to pass intoa collection tank (See Figure 6 in Part IV). The collected slurry is thenpumped through a cyclone device to spin the fine sand from the slur-ry and sometimes through a de-silting unit, and then returned to theexcavated panel or a storage tank. U.S. contractors often providetheir own custom designed units, although high efficiency units arecommercially available throughout the United States and worldwide.

3. Polymer slurries are also used in slurry wall construction and aremixed in accordance with the manufacturer’s recommendations. Aconventional mud mixer is generally used to recirculate the slurry sus-pension prior to its use. Polymer slurries are not desanded since sanddoes not stay in suspension during trench excavation, but falls to thebottom of the panel. Use of modern desanding/desilting equipmentenhances the recycling of the polymer slurry and minimizes the timeneeded for sand to settle to the bottom of the excavation.

4. The cleaning of the bottom of the excavation supported by polymerslurry is dependent on the soil conditions, depth and tools used inexcavation. Mud or sludge may be present at the bottom of the exca-vation. Generally, a smooth blade excavation bucket is used toremove the finer materials that settle and an airlift or a submersiblepump is used to extract the mud or sludge.

5. SLURRY FLUIDS

A. Bentonite slurry is the most common water based slurry used in theindustry. Bentonite slurry is the simplest to mix and maintain and issufficiently versatile for use in most geologic formations and groundwater conditions. Bentonite slurry is prepared by mixing about 6 per-cent of bentonite (clay mineral montmorillonite) by weight with potablewater. The resulting slurry has a viscosity greater than water, pos-sesses the ability to suspend relatively coarse and heavy particles,and tends to form a thin, low permeable filter cake on the sidewalls ofthe excavated trench. Sufficient viscosity and gel strength are impor-tant characteristics to transport excavated material to a suitablescreening system. The sand percentage and specific gravity of theslurry are controlled to maintain the stability of the excavation and toallow proper tremie concrete placement. Bentonite slurry can bemodified using peptizing agents and/or organic additives.

Bentonite should comply with the American Petroleum Institute (API)Specification 13A. Information on the chemistry and mechanism ofslurry wall fluid support of the trench and filter cake development isfound in the references in Part IV.

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B. Polymer slurries have been developed recently and perform well formost slurry wall operations. Polymer slurries are becoming increas-ingly more common in slurry wall construction because of ease of dis-posal and the tendency of suspended soil particles to settle out in thepanel due to the absence of gel strength. Polymer slurries reduce theamount of contaminated concrete at the slurry-concrete interface andresult in less entrapped material at the end stop joint between panels.Because of its low unit weight relative to bentonite slurry, the con-trolled use of polymer slurry is more critical at locations where thereis a high water table, loose soils and where groundwater chemistry isuncertain. Some polymer slurries are composed of natural polymers(guar bean and cellulose materials) and degrade naturally within ashort time. Other polymers are complex chemical elements (vinyl andsynthetic bio-polymers) that are manufactured specially for slurry wallconstruction. Polymer slurry can be treated with special agents todegrade the slurry back to properties similar to water for disposal tosewer systems, if permitted.

C. Bentonite and polymer slurries are sometimes used together in blend-ed slurry to produce less viscous slurry. This procedure enhances thestability of the excavation since fines are present to effectively sealporous soil formations although almost no filter cake is formed. Thebentonite and water are typically mixed and hydrated before the poly-mer slurry is added. Ratios of blended slurry mixtures vary accordingto site-specific demands such as geology and water chemistry.

D. Understanding the chemistry and source of mixing water is an impor-tant factor in controlling the properties of the slurry. Brackish and sea-water are usually avoided. Potable water supply with limited chlorineis more commonly used. Water softeners are sometimes added topotable water sources to limit high acid concentrations and to bringthe water pH to 9.

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6. PHASES OF PANEL CONSTRUCTION

A. The phases of panel construction differ with the type of wall and thetype of slurry fluid selected. Except for precast walls, panels are gen-erally constructed in an alternating panel sequence (See lower sketchin Figure 7 in Part IV) in the following steps:

1. Excavate under slurry fluids,2. Clean the excavated panel, and test the slurry,3. Install end stops or structural shapes,4. Clean end stops of secondary and consecutive panels,5. Place reinforcing cages, if required,6. Install tremie concrete and remove end stops,7. Stress post-tensioning elements, if utilized.

B. For precast concrete panels, the following sequence is usuallyemployed, that follows a primary and consecutive sequence (Seeupper sketch in Figure 7 in Part IV):

1. Excavate under cement bentonite slurry, or with a slurry fluid,2. When slurry fluid is used, it is replaced by a cement slurry. Grout

may be placed at the bottom of the excavation, if required bydesign to support the precast panel and applied loads,

3. Clean ends of previously installed precast panels,4 Install the precast panel. Waterstops can be installed in groves at

ends of panels and grouted to form a barrier to prevent wateringress through the panel joint.

5. Remove temporary panel holding devices and clean or trim thetop of the wall.

6. Install waterstops, if provided, and grout panel joints.

7. INSPECTION, RECORDS AND FINAL CONDITION OBSERVATIONS

A. Inspection

The project owner should contract with a qualified inspector and/orgeotechnical engineer, to inspect the slurry wall installation. Theinspector should have ACI training in concrete testing and reinforcingplacement. See ACI Manual of Concrete Inspection, SP-2 for inspec-tor’s duties, records and reports. The inspector should also haveknowledge of slurry testing procedures and adequate geotechnicalexperience to properly identify the soil types and rock formationsencountered during panel excavation. The contractor should cooper-ate with the inspector in the performance of his quality assuranceduties. The presence of the inspector shall in no way relieve the con-tractor of his obligation to perform the slurry wall installation in accor-dance with the project’s drawings and specifications and with goodconstruction practice.

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B. Records

Accurate detailed records of slurry mixing and its properties in theexcavated panel, materials encountered during excavation, slurrypreparation and mixing, concrete placement and reinforcing cage fab-rication or beam installation are essential. The contractor shall keepindependent records of these operations. The contractor should befully responsible for quality control of the slurry wall operations. Theinspector shall verify that the contractor is maintaining independentrecords. The inspector and contractor should review and reconciletheir records to minimize conflicts. The inspector should keep projectreport forms and verify that the work is proceeding as required by thecontract documents following good construction practices. Sampleforms for recording the inspector’s observations are included asFigures 8, 9 and 10 in Part IV and are described below.

The inspector’s records should include the following general informa-tion on each of the slurry wall panel inspection reports:

1. Name of contractor2. Location on job site3. Date of excavation and completion of guidewalls4. Panel identification number 5. Date that panel approval was given 6. Method of panel construction (conventional, SPTC, precast, etc.)7. Buckets, machines and tools that are employed8. Weather conditions9. Plan and as-built panel dimensions10. Ground elevation at guide wall or reference point11. Plan and as-built elevation of top of panel12. Plan and as-built elevation of the bottom of the panel13. Major soil strata encountered, and their elevations14. Time and date of beginning and ending of panel excavation15. Elevation at which ground water encountered, if any16. Time and date of sampling of subgrade and slurry for sand

content and density17. Time and date of cleaning of joints of secondary and consecutive

panels, if any18. Time and date of beginning and ending tremie concrete

placement19. Slurry property test data20. Time and date of beginning of reinforcing cage or beam

installation21. Concrete slump, pour levels and truck quantities during

tremie operations22. Identification of concrete samples within panel23. Any unusual occurrences

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C. Final Condition Observations

1. When the wall is exposed during general excavation, the inspectorshould check the wall against specified tolerances (See Figure 14 inPart IV). After the wall is exposed and the wall is cleaned, soil andweak concrete should be removed and protrusions beyond the per-mitted tolerance should be removed.

2. Keys and inserts should be exposed and prepared for subsequentuse in the final structure.

3. The inspector should check all panel joints or defects to evaluatewhether they are watertight and will not “blow” at a later stage of con-struction. Leaks at inserts or through vertical joints must be sealed.Defective joints or cracks should be chipped out, cleaned and packedwith rapid setting cement grout mixes. Occasionally, it is also neces-sary to inject chemical or cement grout into the soil directly behind thewall at the location of the leak, or to grout the panel joint directly.

4. Leaks should be sealed with chemicals or cement grout after therelease of the bracing and tieback system supporting the slurry wall.A suitable non-shrink mortar patch and reinforcing should be installedover any abandoned openings or plates in the wall.

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PART II DFI PRACTICE GUIDELINES

1.0 SCOPE

1.1 These guidelines have been prepared for use in the design and instal-lation of temporary and permanent structural slurry walls using ben-tonite, mineral clay or polymer slurry trenching methods. These guide-lines represent good construction practice in slurry wall constructionin the United States.

1.2 Various types of structural slurry walls can be used for temporary andpermanent structures as well as foundation elements. See Figure 11in Part IV for major applications of slurry wall in foundation and marineconstruction. Selection of wall type and reinforcing depends on thetemporary and permanent forces and conditions relevant to thedesign.

1.3 Slurry walls are the best solution when all of their properties are con-sidered in the design of the structure, namely; when they provide lat-eral and vertical support, water cut-off and can eliminate underpinningof adjacent structures.

2.0 CONTRACTOR QUALIFICATIONS

2.1 Slurry walls should only be constructed by companies employing per-sonnel experienced in methods comparable to the specified work.

2.2 Experience should be relevant to anticipated subsurface materials,groundwater conditions, panel sizes, and special techniques requiredfor slurry fluids and excavation tools.

2.3 The contractor should demonstrate to the satisfaction of the owner’srepresentative the availability and dependability of equipment andtechniques to be used on the project.

3.0 SUBSURFACE INVESTIGATION

3.1 A thorough geotechnical investigation of the site should be performedprior to the start of design.

3.2 Adequate geologic information should be obtained for design andconstruction purposes. The exploratory information may consist ofthe following; borings with “disturbed” or “undisturbed” methods, rep-resentative soil samples and their descriptions, Standard Penetration

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(Resistance) Tests (SPT), laboratory tests with grain size distributionand Atterberg limits, moisture content and density tests, rock coresamples and recovered core barrel piece lengths expressed in per-centage of the total core run (RQD) and rock core hardness andstrength, descriptions of rock weathering pattern, orientation of bed-ding planes, joints, fractures, solution channels insoluble rocks suchas limestone and inclusions. These tests need not be performed forevery project. Information should be sufficiently detailed to delineateobstructions and variations in soil and rock material properties.

3.3 A geotechnical report should be provided to the contractor during thebidding period.

The three most typically used geotechnical report formats [6] are asfollows:

• Geotechnical data report (GDR): A compilation of facts, such asboring logs and laboratory tests, excluding any interpretations.

• Geotechnical interpretive report (GIR): The geotechnical engi-neer’s interpretation of the data, including profiles of regionalgeology and interpretation of site-specific data that may help pre-dict what is likely to be found underground.

• Geotechnical baseline report (GBR), sometimes referred to as ageotechnical design summary report (GDSR): The design engi-neer’s interpretation of the anticipated geological conditions andthe expected behavior of the ground during construction Thisreport establishes “baselines,” quantified measures of estimatedground behavior parameters. Such baselines permit bidders toformulate bids on certain ground conditions, with the understand-ing that if the actual ground conditions are more or less adversethan the baseline, the owner will consider modification to the con-tract under the differing site condition (DSC) clause.

3.4 Soil and rock samples collected during subsurface explorationsshould be preserved at natural moisture content and arranged so thatthey can be readily examined. The samples should be kept at somecentral location, such as the owner’s office.

3.5 Groundwater levels should be measured and recorded in borings andpiezometers that may indicate whether natural or artesian water lev-els are present at the project site.

3.6 It is recommended that the owner employ and pay for all geotechni-cal services required. A conflict of interest could occur if these serv-ices are provided and paid for by the contractor.

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3.7 The contractor should notify the owner if in his opinion the availablegeotechnical information is inadequate to bid and to plan the work.

3.8 The contractor may perform additional soils exploration to improve hisknowledge of site soil and rock conditions, if permitted by the owner.

4.0 DESIGN AND SITE CONSIDERATIONS

4.1 There is no single code in the United States that fully applies to slur-ry wall applications. The designer must therefore select the mostapplicable codes and standards, such as American Concrete Institute,American Institute of Steel Construction, The American Association ofState Highway and Transportation Officials and American RailroadEngineering Association, ASCE Design Loads on Structures DuringConstruction, local building codes and project standards. Many ofthese codes do not deal with specific regulations for temporary struc-tures. For this reason, the designer should provide the proper guide-lines for the contractors upon which to base their bids.

4.2 All design should be performed by qualified licensed professionalengineers utilizing contemporary design procedures that are in accor-dance with good engineering practice. See Bibliography in Part V forcommonly used design references.

4.3 Existing utilities and structures should be indicated in contract docu-ments and verified. The presence of pre-existing structures or aban-doned utilities should be also identified. Groundwater monitoring isstrongly advised during and after slurry wall construction and generalsite excavation.

4.4 The design should consider all loads on the wall due to at-rest, activeand passive soil pressures, water and seismic loads and their effecton soil strength, surcharge effects, loads resulting from connection toa structure, effects of wall movements during and after construction,soil mass effecting the global stability of the wall, as well as the effectsof wall support systems such as struts or tiebacks. All design loadsand load combinations should be clearly identified in the computa-tions.

4.5 Adequate safety factors should be provided considering the nature ofthe load, its duration and the effect of the load on the temporary andpermanent performance of the wall. Reductions in safety factor maybe applied to temporary walls, to combinations of transient loads[dead load + live load + wind], to loads of infrequent occurrence [floodor earthquake] in combination with service loads. Safety factors andload factors should not be compounded, that is, applied to the loads,

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then to the structural design of the wall using already factored loadsand then to the support system using already factored wall loads.Safety and load factors should consider the variability of geotechnicaldesign parameters, which affect the wall design and support systems.

4.6 When Allowable, Load Factor and Ultimate Design Methods are used,the design should take into account the effects of incompatibility of themethods, particularly with regard to analysis and the use of safety andload factors. Increases in the basic allowable stresses should beapplied to bending members and secondary compression memberssuch as walers. Estimates for deflections of walls should considerpossible uncracked or cracked section properties that result duringstaged excavation and should be based on non-factored loads.Increases in allowable stresses should not be applied to compressionmembers such as struts.

4.7 Structural design of the wall should be in accordance with all currenteditions of national and local building codes and relevant sections ofthe American Concrete Institute, the American Institute of SteelConstruction, the American Association of State Highway andTransportation Officials and American Railroad EngineeringAssociation codes.

4.8 Effects of in-plane and normal loads should be considered in thedesign of the wall. The combined effect of these loads should notexceed code limits.

4.9 The design layout of slurry wall panels may affect adjacent structuresor utilities. The design shall indicate that special excavation proce-dures, tools, reduced panel lengths, underpinning, grouting or groundtreatment may be required to protect or limit wall movement nearthese structures or utilities.

4.10 The design should account for residual stresses resulting from tempo-rary stages of construction and their effect on the serviceability andlong-term performance of the wall.

4.11 Compatibility of wall movements should be considered when select-ing wall support systems, wall reinforcement and panel jointing meth-ods.

4.12 Specially designed details should be provided where loads are to betransferred across joints.

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4.13 Construction documents, whether prepared by the consulting engi-neer or the contractor, should clearly define the scope of the work;indicating, where relevant, the thickness of the wall; panel lengths; thelocation of the wall in plan; dimensions or elevations of the top andbottom of the wall; size, position and length of reinforcement; positionof all keys and inserts and location and magnitude of temporary sup-port loads.

4.14 Specified wall tolerances, finishes and reinforcing cover should con-sider site geology (i.e. boulders and cobbles) and exposed depths ofwalls. See Section 12.0, for tolerances commonly used in the U.S.

4.15 Wall monitoring and instrumentation should be utilized to verify walldesign parameters and to record performance of wall systems. Duringgeneral site excavation, wall and bracing systems, as well as expect-ed and critical structures adjacent to the site should be carefully mon-itored and the parties responsible for design and construction shouldreview and respond to discrepancies in performance.

5.0 MATERIALS

5.1 Concrete should meet the specified minimum compressive strength(f’c) at 28 days, usually between 3000 psi and 5000 psi, at a slumpranging between 7 and 9 inches. Approved plasticizing agents, fly ashand/or air entrainment may be used to improve the workability of themix. Water to cementitious materials ratio should not exceed 0.6.Normal low range plasticizers are recommended for producing work-able concrete mixes. The use of super-plasticizers in concrete mixesis discouraged because of the short time of extended slump workabil-ity due to temperature changes between the times of concrete place-ment and when the superplasticizer is added to the mix plant. Forwater containment structures or special wall exposures, the watercement ratio can be adjusted to the standards of the applicable codesor standards of good practice only if the workability of the mix is notaffected.

5.2 The aggregates used in the mix should be limited to 3/4-inch to 1-inchsize, well graded, durable and inert, with hard rounded gravel and asandier mix preferred.

5.3 Concrete should be proportioned, mixed and placed in accordancewith ACI and other relevant codes and recommendations.

5.4 Steel reinforcement should consist of new deformed billet steel barsconforming to the requirements of ASTM A615, Grades 60 and 75 orrolled steel shapes conforming to the requirements of ASTM Grade-A36 (currently not being rolled but may be available), or ASTM A-572,A-588 or A-992, Grades 50 and 60 or equivalent metric standards.

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5.5 Reinforcing steel cages should be detailed as simple as possible.Multi-layers of bars on faces of cages, complicated bends, splices,cutoffs and grade and size changes should be avoided. Cages shouldbe securely tied with wire. Welding of interconnecting bars or attach-ments should be discouraged. The steel cages shall be rigid enoughfor lifting during construction and may require additional reinforcingsteel beyond that required for design.

5.6 Inserts and keys for walls and floors and grout pipes for post groutingshould be accurately located and tied to the cage. Any pipes or tubesfor geotechnical instrumentation should be attached per manufactur-er’s recommendations. Adequate room for placement of tremie pipesand minimum clear spacing of adjacent bars to facilitate concreteplacement must be considered in the design and reinforcing cage fab-rication. Special threaded bars or crimped bar block-outs should beconsidered for more densely packed reinforcing cages. In corrosiveconditions, epoxy coated or galvanized reinforcing bars should beconsidered.

5.7 Provision should be made for field alteration of cages if variations inpanel dimensions are anticipated. Suitable spacers or rollers shouldbe attached to the cage to maintain the required concrete cover.Round concrete blocks on steel bar axles, spacers that do not scrapeor dig into soil faces or non-metallic devices are recommended.

5.8 Bentonite and other mineral clays should conform to the requirementsof American Petroleum Institute (API) 13A. Chemically treated ben-tonites may be required to counter the effects of contaminated soil orground water. Chemical additives should not be applied to bentoniteslurry at the trench. Chemical additives may be added at the mixingplant under controlled conditions and to meet clearly defined objec-tives.

5.9 Polymer slurries used for trenching can be specially treated organicmaterials or chemical compounds. The specific conditions of the soiland groundwater regime should be considered with highly acidic andalkaline conditions avoided. Special slurry handling and disposal pro-cedures should be considered and monitored for the duration of thewall construction.

5.10 Water used in the preparation of bentonite slurry should be neutral,clean, fresh, and free from oil, alkali, organic matter or other deleteri-ous matter. Monitoring of the groundwater and its chemistry is usual-ly performed when aggressive soil conditions or contaminated groundwater or fluids are found.

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6.0 SLURRY FLUIDS

6.1 Freshly mixed bentonite should have a minimum unit weight of 64pounds per cubic foot (pcf), measured using the mud balance, mini-mum viscosity of 32 seconds, measured using the Marsh Funnel; fil-trate loss of less than 25 cc using the standard filter press; and pHbetween 7 and 11.5. More viscous slurries or plugging agents may berequired where high slurry losses are expected.

6.2 In typical wall installations, bentonite slurry properties are adjusted tohave a maximum unit weight of 70 pcf, maximum viscosity of 50 sec-onds, maximum sand content of 5 percent prior to placement of con-crete, all measured 2 feet above the bottom of the panel excavation.When conditions for conventional work are affected, e.g. panel depthis significantly deep and/or the volume and rate of the tremie concreteplacement are not sufficient to displace the bentonite slurry, the sandcontent of the slurry can be reduced to about 1% to 2% to improve thehorizontal flow of concrete throughout the panel. Similarly, if the panelis designed for load bearing in soil or rock, the sand content shouldbe at the lower level and then tested at closer intervals along thelength of the panel.

6.3 Polymer slurries should exhibit a maximum unit weight of 64 pcf, vis-cosity of 40 to 90 seconds, and maximum sand content of 1%, meas-ured 6 inches above the bottom of the panel.

6.4 Slurry liquid should be carefully controlled and its properties tested bya slurry specialist or qualified engineer throughout the duration of thework.

7.0 GENERAL SUBMITTAL REQUIREMENTS

7.1 Shop drawings should be submitted showing guide walls, panel lay-out, dimensions and numbering scheme, sequence of panel installa-tion, end stop detail, protection of structures and utilities, reinforcingsteel details, location and detail of all inserts and keys or any otherembedded item.

7.2 A statement should be submitted indicating methods of monitoringadjacent structures, trench stability, plumbness and deviation, includ-ing corrective measures, if necessary.

7.3 Time schedule, equipment schedule and list of specialized personnelshould be submitted.

7.4 Detailed description of contractor’s quality control program should besubmitted.

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7.5 Bentonite, mineral clay and polymer slurry mix and manufacturer’stest reports for material to be supplied should be submitted.

7.6 Concrete mix design should be submitted including name of supplier,proportions, gradation, and test results of ingredients. Laboratory trialmixes are recommended, except where local practice has developedsignificant experience with available standard mixes.

7.7 Engineering calculations, drawings and details of contractors’designed portions of the work should be prepared by a licensed pro-fessional engineer experienced in the relevant design and construc-tion. Engineering calculations may be required to evaluate the effectof staged construction, construction induced loads; and contractor orfield changes affecting the design of the temporary lateral supportsystem.

7.8 Resumes of experienced personnel should be submitted as required,including information on each type of wall project, employer, supervi-sory duties held and/or field duties performed, and years of experi-ence.

7.9 Contractor’s slurry wall project summaries should be submitted asrequired, including project name, owner, engineer, contact person,dates and descriptions of walls completed, and a list of projects per-formed as joint ventures.

7.10 Equipment summaries should be submitted as required, includingavailable mechanical or hydraulic bucket sizes, drills, chisels, operat-ing cranes, slurry storage facilities, mixing and distribution systemsand concreting equipment.

8.0 PREPARATION FOR EXCAVATION

8.1 Utilities and structures in the vicinity of the wall should be located, pro-tected, maintained and restored. The surface of adjacent structuresshould be covered and protected from the spillage of soil, bentonite orconcrete. All utilities and man-made obstructions within the alignmentof the slurry wall should be removed or capped or relocated asrequired. Utility information should be checked with local authoritiesand utility companies. Test pits and careful pre-trench work should beperformed where accurate records are not available.

8.2 Install continuous, reinforced concrete guide walls to the line andgrade of the finished wall providing sufficient clearance betweenguide walls to permit passage of the excavation tool. See Figure 12 inPart IV for typical guide wall construction details. Provide temporary

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guide wall bracing to maintain correct position and clearance duringexcavation. The guide walls should be carried down to the level of thelowest adjacent utility or structure. The location of panel joints shouldbe clearly marked on the guide walls.

8.3 Top of guide walls should be set a minimum 5 feet above the highestanticipated natural groundwater level. A stockpile of material shouldbe provided to backfill the excavation in the event of flooding or anunanticipated rise in the groundwater level.

8.4 Guide walls should be founded on suitable soil for bearing purposes.In some circumstances, the bearing layer may not be suitable for thesupport of the guide walls. Some contractors prefer to prepare a leanconcrete fill as the founding subgrade for the guide walls (See Figure13 in Part IV).

Note: Information obtained from references [7, 8, 9 and 10] has beenused extensively in Sections 9.0 through 15.0.

9.0 EXCAVATION

9.1 Excavation equipment contractor should be provided that is capableof removing all soil, fill and rock materials encountered within thealignment of the wall. Man-made obstructions are typically removedin the pre-trenching process prior to constructing the guide walls.Clamming, drilling, scraping and grinding methods may be employedsubject to environmental constraints such as spillages, excess noiseand vibration.

9.2 Excavation should be conducted in a continuous manner to therequired lines and grades with a minimum of two unexcavated panels,usually a minimum of 30 to 40 feet, or one concreted panel usually 15to 20 feet separating any open panels. Excavation should not be per-formed adjacent to concrete placed within the preceding 24 hours,except where necessary to remove stuck stop end devices.

9.3 Sufficient survey control should be provided to assure that the panelexcavation conforms to the required alignment and tolerances for ver-ticality and position. The contractor should measure verticality andhorizontal position at regular intervals approximately 15 to 20 feetapart. Wires connected to the teeth or side lugs of the clamshell buck-ets or built-in slope inclinometers within specially fabricated bucketstied to the operator’s controls can be used to judge the clamshellbucket’s position, referenced to the guide walls. Also, electronic read-out and control devices in the crane’s cab can be used to determinethe correct alignment and prevent “corkscrewing” as the excavation

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proceeds downward. More precise measurements, using sonicdevices or spiders, can provide a profile of the faces of the panel afterthe excavation is completed. These measurements can verify theminimum wall thickness and clearance to install reinforcing, beamsand end stops. In deep excavations, verticality is critical to the effec-tive connection of adjacent panels. In thin wall applications with deeppanels, the verticality tolerance of the excavation may be restricted to0.5 percent or less depending on design requirements.

9.4 Wall embedment (“socket”) in suitable bearing soil or rock should beverified in the presence of the inspector. Soil or rock samples may berequired at closer intervals where change of geotechnical formations,anomalies or large boulders is encountered to verify that proper sock-ets are achieved. All sockets should be verified and the bottom of thepanel thoroughly leveled and cleaned prior to placement of reinforc-ing and concrete. The use of toothless buckets, specially designedpumps and airlifts are generally used for cleaning sockets.

9.5 Panel depths should be measured at the start of each day to check ifcave-ins occurred overnight. Final panel depths should be verified atshort spacing along the bottom of the panels to ensure that structuralelements will be installed properly. The inspector should verify thebottom of the panel by using a weighted line or rod to ensure that nosand residue or rock fragments is at the bottom of the panel.

9.6 Bentonite slurry should be provided in a continuous manner in orderto assure that the excavated trench is always full to within 2 feet of thetop of the guide walls. A sufficient supply of bentonite slurry or back-fill should be maintained to assure trench stability in the event ofunanticipated losses of slurry. Bentonite slurry should be constantlymonitored to assure that the slurry conforms to specification require-ments and will perform its intended function and excavation does notresult in danger to adjacent structures and utilities.

9.7 Fresh mineral slurries should be mixed with suitable colloidal mixers.Water for mineral slurries shall be potable and free of deleteriouschemical substances, which can affect the slurry properties. Slurriesshould be stored in lined ponds or storage tanks to permit properhydration. The contractor should establish a quality control laboratoryon site to perform periodic testing to assure the slurry is suitable forits intended purpose.

9.8 Freshly stored slurries should be tested for density, viscosity, filtrationand pH. The slurry in the excavated panels should be tested daily forspecific gravity, viscosity and, near the bottom of the panel, for sandcontent. See Figure 9 in Part IV for a typical Slurry Fluid Test ReportForm.

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9.9 Proper cleaning of the slurry in non-contaminated ground will permitmultiple re-uses. Contaminated ground, calcium from tremie concreteoperations, or poor cleaning can affect the slurry properties, requiringthe early disposal of slurry. The contractor should carefully control,monitor and isolate the slurry from multiple uses in various panels.

9.10 A slurry sampling tool with a special bottom entry only flap should beused to take slurry samples from the bottom and mid-height of theexcavation at any time to ensure that accumulated materials or sludgelike material does not affect the excavation and tremie concrete oper-ations.

9.11 Polymer slurry should be maintained and monitored in a continuousmanner similar to bentonite slurry, except that filter cake will not devel-op on the trench walls. The collection of solids at the bottom of thepanel should be made with a toothless clamshell bucket. Chemicaltreatment may be needed for special polymer slurries.

9.12 Excavation spoils and waste bentonite should be disposed of in anenvironmentally sound manner.

10.0 REINFORCEMENT PLACEMENT

10.1 The slurry fluid should be tested, modified and cleaned as necessaryand the bottom and sides of the panel should be measured andcleaned prior to the placement of stop end devices and the reinforce-ment. Reinforcement (steel rebar cages and/or structural beams)should be placed as soon as possible after cleaning of bottom of thepanel, or not more than 3 hours after testing of the slurry fluid for sandcontent and sedimentation.

10.2 End stop devices in primary and consecutive panels should besecurely fastened in position and the cage, beam, and panel dimen-sions verified prior to lifting and installing the cage. All loose rust, oilor other deleterious material should be removed from the reinforce-ment.

10.3 Structural beams and reinforcing bar cages, if required, are usuallyfabricated on site, on the ground for installation within the panel. Thecage is fabricated by connecting individual bars with tie wire, chairsand spacers. Blocks, rollers or other devices are added to provide theconcrete cover as needed. The location of the tremie pipe(s) shouldbe considered and rebar placed clear of the tremie pipe locations.Welding of rebar is usually discouraged. Beams are usually fabricat-

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ed and stiffened by frames located within the panel. The framesshould permit the free flow of the tremie concrete, but still maintain theposition of the vertical beams. The beams are inserted into the paneland the cage is then hung from the guide walls. The contractor shouldprovide additional stiffening elements within the panel for lifting thecage upright and tying block outs, instrumentation attachments, floorand wall keys, tieback trumpets and bearing plates, etc.

10.4 Sufficient slings, lines and equipment should be provided to preventpermanent distortion of the cage. The cage should be supported fromthe guide walls in correct position and 6 inches clear of the bottom.Local trimming, cutting, narrowing and other modification of the cage,which may be required to accommodate misalignment of the excava-tion, should not be done without the approval of the engineer.Repositioning or retying of loose bars, inserts, keys and other devicesmay be required during lowering of the reinforcement.

11.0 CONCRETE PLACEMENT

11.1 Prior to concreting the previous cast joint of secondary and consecu-tive panels should be scarified and carefully cleaned. Concreteshould be placed shortly after testing for sand content and within 3hours of placement of the reinforcement or 24 hours after cleaning theexcavation. If a delay occurs, then slurry should be retested to meetthe test limits or the slurry replaced. Once started, concrete place-ment should proceed continuously until uncontaminated concrete hasreached the required top of wall elevation. Detailed records of thequantity, quality and rise of concrete in the panel should be main-tained. Adequate equipment should be provided to assure an uninter-rupted supply and placement of concrete, even in the event of equip-ment breakdown.

11.2 The contractor should ensure that the rise of the concrete is fairly uni-form along the top of the rising concrete and that blockage of thetremie pipe does not occur. See Figure 10 in Part IV for a typicalTremie Concrete Inspection Report Form. Concrete shall be placedby tremie methods in such a manner that the concrete displaces theslurry progressively from the bottom and rises uniformly to the sur-face, such that intermixing of the concrete and slurry will not occur. Ifa “go-devil” or plug is provided to minimize the initial mixing of con-crete and slurry, care should be taken that it not be entrapped in theconcrete or otherwise cause a defect in the concrete.

11.3 The contractor should control concrete placement by truck deliveries,pumping and by more careful control using two tremie pipes for stan-dard panels, except SPTC panels (See Photo 13). For SPTC panels,

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a tremie pipe should be provided for each beam element where mul-tiple soldier piles are used to form a panel. The use of the “go devil”or starter plug, is usually not employed with tremie concrete place-ment. The contractor should revise his procedures if cold joints devel-op or if intermixing of concrete and slurry occurs. The use of a super-plasticizer in concrete mixes has potential problems, limiting the peri-od of desired slump and concrete placement within the tremie pipes.This placement should be carefully monitored and controlled.Concrete mixes furnished by suppliers should be suitable for the con-tractor’s placement methods. The contractor is responsible for anydefects within the panel that may occur during concrete placement.

11.4 The tremie pipe should be 8 to 10 inches in diameter and shall beembedded a minimum of 5 feet and a maximum of 15 feet into freshconcrete. Surging of the pipe may be required during placement.Care should be taken to assure that the pipe is always embedded infresh concrete and that loss of the tremie seal does not occur andresult in a cold joint.

11.5 Where two tremie pipes are used, care should be taken to assure thatboth pipes are always of equal length, that a sufficient number oftrucks is always available to charge both tremie hoppers uniformlyand that the concrete level at each pipe is essentially level. The useof more than two tremie pipes should be discouraged for standardpanels, except SPTC panels.

11.6 End stop devices should be withdrawn in a smooth and continuousoperation after the initial set of the concrete. The contractor and theinspector should determine the suitable rate of withdrawal by check-ing set times of sequential batches of concrete selected from deliverytrucks. In some instances when using laterally extractable end stops,the end stop removal sequence may be different.

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Photo 13: Tremie concreteplacement operations inWashington DC.

Courtesy of the Architect of U.S. Capitol

11.7 Extra concrete cylinders may be taken during placement so thatunusual conditions or suspected samples with low strength concretebreaks could be checked at a later time. Concrete cylinders shouldbe protected from freezing and from vibration during their transport tothe lab.

11.8 Concrete strength, if disputed, can be verified by coring and testingconcrete from the wall at a later time.

12.0 TOLERANCES

12.1 Panel joints should be within 6 inches of the correct position and with-in 1% of vertical if not specified otherwise.

12.2 The overall out-of-plumb tolerance of the reinforcing cage andattached assemblies perpendicular to the plane of the wall should notexceed 1% of the depth of the wall at the depth measured and 3 inch-es in any direction in the plane of the wall. See Figure 14 in Part IVfor standard tolerances. More rigorous verticality requirements of upto 0.5% may be required to assure proper overlap of panels in deepwalls. The use of clamshell buckets or hydromill excavators in vari-able soil or rock conditions should be properly controlled to meet suchstringent tolerance. In rare instances for dam construction, verticalityhas been controlled with special equipment to 0.2% verticality.

12.3 The minimum concrete cover should be 3 inches. An additional toler-ance of 3 inches beyond the minimum concrete cover should be lim-ited to areas not critical at the exposed surface of the wall.

12.4 Construction accuracy and wall finishes depend on site soils, equip-ment used and the skill of the contractor. Tolerances may be relaxedor walls set farther from neat lines where walls are constructedthrough loose, bouldery soils or fills consisting of piling, timbers, dem-olition or other loose debris, or where walls are temporary and are suf-ficiently clear of permanent construction.

13.0 DIFFERING SITE CONDITIONS

13.1 In the absence of a contract clause for differing site or changed con-ditions, the following procedures are recommended when conditionsare encountered in the performance of the work which differs fromthose indicated by contract documents (including the geotechnicalreport) or ordinarily recognized as inherent in work as described in thecontract.

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13.2 A written notice to the appropriate owner’s representative should begiven promptly when encountering these conditions.

13.3 An equitable adjustment and time extension notice should be dis-cussed with all parties to cover the resulting extra unanticipatedscope, change in schedule and associated costs.

14.0 COMPLETION OF THE WORK

14.1 All loose bentonite, soil and laitance should be removed from the topand face of the wall. Top of wall shall be trimmed to finished eleva-tions. Embedded water stops at the top of walls are usually difficultto execute and are not recommended. Keyways for extension of thewall should be carefully cut into sound concrete and waterstops prop-erly installed.

14.2 All leaks should be sealed or patched in order to provide for therequired “watertight wall”.

14.3 Misalignments, bulges, protrusions and cavities should be broughtinto conformance with the required tolerances and should berepaired.

14.4 All existing structures and utilities should be restored to their precon-struction condition.

14.5 Collect and secure all construction records relating to bentonite slur-ry quality, excavation, reinforcement, concreting and repairs.

14.6 Contaminated and excess bentonite slurry and excavation spoilshould be removed to an offsite location in a safe, lawful manner. On-site disposal may be permitted upon receipt of relevant owner or localauthority approvals.

15.0 WATER TIGHTNESS CRITERIA

15.1 There has been continuing improvement in the quality of slurry wallconstruction, however, there is a common misconception amongstspecialist contractors, owners, designers and project managers as tothe degree of watertightness that can be expected. The constructionindustry and interested parties acknowledge the difficulty of producingslurry walls that don’t leak, or have minimal seepage, however, thereis no industry wide acceptance criterion for the water tightness of slur-ry wall systems. Project documents usually require that the slurry wallsystem not leak, show running water and/or contain material inclu-

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sions or defects in panels and joints. Clearly, the specialist contractorshould address these problems if they occur. Running water on thesurface of the wall, at joints or at inserts in a panel, is not acceptable,however, a slurry wall may exhibit patches of moisture, [like beads ofsweat] and still be considered “impermeable” or “watertight”.

15.2 The watertight quality of slurry walls can be affected by cracks andmovement at panel joints that form due to structural deflections and/ordifferences between panel support conditions, by floor openings,embedded tieback anchors and internal waling within the slurry wall.Even fairly thick concrete slurry walls allow some transmission ofwater, although the amount of water is relatively low in shallowaquifers and low permeability soil conditions. A simple calculationusing Darcy’s Law of water passing through a 2-foot thick, fairly denseand homogeneous concrete wall with a 30 foot head of water wouldindicate a flow of 0.5 gallons per 10,000 sq. ft. of wall per 24 hours.

15.3 There is no standard industry criterion on how to minimize moistureand dampness in underground structures. Some building basements,parking structures, mechanical and electrical rooms, subways andother tunnels can sometimes tolerate moisture or dampness.Sensitive below grade uses, such as habitable spaces, medical, food,and computer or document storage do not permit dampness or mois-ture and exceptionally dry environments are desired. It is question-able whether or not it is necessary to have the highest degree of watertightness specified for all slurry wall structures.

15.4 If required for the proper functioning of the underground space for theservice conditions, there are six ways to achieve the highest possiblelevel of water tightness. They include:

1. Watertight concrete construction relying on well thought outdesigns and the highest quality of slurry wall construction.

2. Sealing all panel joints and fixing faulty construction adequatelyafter temporary bracing has been removed, and the slurry walland structure has stabilized.

3. The use of liner walls cast against the slurry wall. 4. Cavity wall construction with provisions for drainage, sumps and

ventilation.5. The application of interior waterproofing using membranes or

spray on waterproofing applied after the walls have been repairedand sealed.

6. The use of water stops cast into the panel joints and other con-nections exposed to water.

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15.5 While it can be debated as to the need for the use of the above meth-ods, there is no straightforward way to estimate the quantity of water,dampness or moisture that is acceptable. The design and expectedslurry wall water tightness should be carefully planned and presentedin the contract documents so as to avoid construction disputes and lit-igation.

16.0 COMPENSATION

16.1 Payment is usually made on a unit price basis, as measured bysquare feet of vertical wall face. This measurement should include theactual area between the top of (sound) wall and the bottom of wallindicated on the drawings, or as directed by the engineer. Plan meas-urement should be made along the centerline of the wall.Measurement of the bottom of the wall depths is made by (rigid) rodsor sounding devices at 2 feet intervals. No payment should be madefor walls installed beyond these limits. Payment usually includes allcompensation for furnishing materials, labor, equipment, tools andincidentals required to complete the work. The contract price shouldalso include all panel excavation, watertight joints, reinforcing steelbars, supply of embedded items, tremie concrete, guide wall con-struction and removal, supply, handling and disposal of slurry fluids,hauling of excavation materials, trimming of the top of the wall,removal of unsound concrete, removal of bulges or projections, andsealing or grouting of the wall for watertightness.

16.2 Payment for the slurry wall should be made against pay units estab-lished in the contract. Separate pay units may be established forremoval of rock, boulders or obstructions, concrete overruns, slurrylosses, reinforcing steel, inserts or embedded items, guide wall instal-lation and slurry disposal. Absent such provision, no separate pay-ment should be made.

16.3 As much as ten percent of the slurry wall contract price is oftenretained until the wall is fully exposed and found to be in conformancewith contract requirements. Unexposed slurry cutoff walls may haveanother criteria for retaining payment (e.g. measurement of specificperformance provisions, permeability or movement) as required byproject provisions.

16.4 Confirmatory soil borings or rock cores, when required by the con-tract, should be paid on a unit price basis per linear foot and unit pricefor each soil sample or rock core drilled.

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PART III DEFINITIONS

A

ACI: American Concrete Institute.

Airlift: Device for lifting slurry, suspended solids and drill cuttings from the bot-tom of a bentonite or polymer slurry filled trench. Usually, compressed air isintroduced into the slurry at the bottom of the trench using a small pipe insideof a larger pipe. This upward flow tends to lift material from the bottom of thetrench.

API: American Petroleum Institute

API Spec. 13A: API Specification for Oil Well Drilling-Fluid Materials.

API Spec. 13B: API Recommended Practice, Standard Procedure for TestingDrilling Fluids.

ASTM: American Society for Testing and Materials.

Auger Drill: Helical device used to scrape, grind and/or dig into soil and rock.

B

Barrette: See Load-Bearing Element.

Bentonite: Montmorillonite clay containing sodium cations formed primarilyby in-place alteration of silicate rocks of volcanic origin.

Bentonite Slurry: Mixture of bentonite and water.

Berm: Sloping surface of soil providing lateral support to wall.

Blockout: Device to form recess in wall.

Bond: Adhesion of concrete to reinforcing steel.

Brace: Linear structural element used to provide lateral support to the wall,positioned perpendicular or at an angle to the wall.

Brace Plate: Steel plate embedded in wall to receive brace and transfer loadfrom wall to brace.

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C

Cable-hung Clamshell Bucket: Excavation bucket operated by cables.

Cage: Network of interconnected reinforcing steel bars.

Cake: See Filter Cake.

cc: Cubic centimeter. Metric unit of volume.

Cement Bentonite: Low strength mixture of cement, bentonite and water,which hardens with time.

Cement Grout: High strength mixture of cement and water, which hardenswith time.

Chisel: Heavy steel tool used to soften or fracture rock or obstructions.

Clamshell Bucket: A mechanical bucket operated by two cables from a craneor rig. In some cases hydraulic cylinders may be used on other types of buck-ets. Spoil is removed from the bucket by swinging it to one side of the trenchand releasing the closing lines of the bucket.

Chemical Grout: Mixture of chemical compounds, which become more vis-cous and/or harden with time.

Churn Drill: Fixed boom-drilling machine, which raises and drops a chiselused for rock excavation.

Closed Specification: Specification, which describes the end product andhow it is to be achieved. Usually, used for permanent walls.

Cofferdam: Excavation support system. Usually, used to inhibit the entry ofwater.

Cold Joint: Discontinuity in concrete caused by a disruption in the placementof tremie concrete.

Concrete Cover: Distance from closest reinforcing bar surface to the face ofthe wall surface.

Consecutive Panel: Panel cast with one end against a previously cast panel.

Corner Panel: Panel, not linear in plan, used to accomplish change in direc-tion of wall.

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Conventional Panel: Panel cast with one or two end stops, except for SPTCand precast panels.

Cutoff Wall: Non-structural wall used to inhibit the movement of water.

Cyclone: Centrifugal device used to remove fine soil particles suspended inbentonite slurry.

D

Desander: Device used to remove sand and silt particles suspended in ben-tonite slurry.

Design Drawing: Drawing prepared to show intent of the work. Drawing is notsufficiently detailed to permit construction.

Diaphragm Wall: See Slurry Wall.

Direct Circulation Drill: Hollow stem chisel with provision for application ofbentonite slurry under pressure at the head of the drill in order to remove drillcuttings.

Dowel: Reinforcing steel bar projecting from the top or face of the wall intend-ed for connection of reinforcement or concrete at a later time.

Drainage Chase: Space provided between slurry wall and interior finish wallfor collection of seepage from slurry wall.

E

End Pipe: See End Stop.

End Stop: Round pipe or shaped device placed at ends of panel excavationprior to placement of concrete and withdrawn from excavation after concretehas set, providing smooth surface at ends of panel.

End Stop Extractor: Device to withdraw end stop after concrete hasachieved initial set.

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F

Filter Cake: Thin layer of hydrated bentonite gel, which forms on the soil faceof the excavation.

Filter Press: Device used to measure the filtration and filter cake develop-ment of bentonite slurry.

Filtrate Loss: Water loss from bentonite slurry applied under pressure againsta filter.

Flocculation: Condition where dispersed clay particles form agglomerates orclumps.

G

Go Devil: Device placed in tremie pipe prior to placement of concrete intopipe. Device is intended to prevent concrete from mixing with bentonite slurryduring initial placement of concrete.

Grab: See Clamshell bucket.

Grout: A mixture of cement and water or sand and chemicals, used for fillingvoids. It is typically made for pumping under pressure.

Gel: Semi-rigid colloidal suspension of a solid in a liquid.

Guide Walls: Shallow concrete walls placed on either side of the alignment ofthe slurry wall to provide vertical and horizontal alignment control for the exca-vation and subsequent support of the reinforcing steel cage and/or other ele-ments to be placed in the trench.

H

Hydraulic Clamshell Bucket: Excavation bucket operated hydraulically.

Hydromill Excavator: Reverse circulation drilling/grinding machine operatedby hydraulic drives to rotate cutter wheels on a horizontal axis. The spoil isremoved by a submersible pump within the framework of the machine.

Hydrofraise: See Hydromill Excavator

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I

Insert: Any device intended to be permanently embedded in the wall.

Instrumentation: Any device intended to measure the performance of thewall.

Internal Waler: Reinforcing steel embedded in the wall to provide bendingresistance between points of lateral support.

J

Joint: Discontinuity between panels usually formed by end stops or embed-ded structural shapes.

K

Kelly-Bar: Vertical shaft used to transfer torque from a power unit to a rotarytype drill, or to raise and lower a clamshell bucket.

Key: A recess in the wall intended to receive a wall or floor slab.

L

Laitance: Contaminated concrete which forms at the top of the tremie con-crete as a result of the mixing of concrete and the bentonite slurry.

Lean Concrete: Low strength concrete usually intended as backfill in situa-tions where the material will be subsequently removed.

Lifting Sling: Cable device used to lift reinforcing steel cages with minimaldistortion.

Liner Wall: Interior finish wall placed in contact with or separated from theslurry wall.

Load Bearing Element: Element constructed in various plan configurationsand intended to primarily carry vertical loads.

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M

Man-made Obstruction: Any below ground man-made object, such as con-crete, timber, building rubble, abandoned utilities, which cannot be easilyremoved by clamshell bucket. It requires removal by chiseling, grappling orthe use of special mechanical devices.

Marsh Cone: See Marsh Funnel.

Marsh Funnel: Cone shaped funnel used to indirectly measure bentonite slur-ry viscosity by measuring the time of passage of a quart of slurry through aspecified opening size.

Milan Method: See Top Down Method.

Milling Machine: A reverse circulation, rotating, grinding device used to exca-vate hard ground or soft rock. See Hydromill Excavator.

Mixing Plant: Combination of mechanical devices used to mix, store, cleanand/or distribute bentonite slurry.

Montmorillonite: A principal clay mineral group. A hydrous aluminum silicatecharacterized by a crystalline structure of layers or thin sheets. This is themain ingredient of bentonite clay.

Mud Balance: Scale device used to measure unit weight, specific gravity ordensity of slurry.

O

Over-break: The difference between the actual amount of concrete placedand the neat theoretical volume. Usually expressed as a percentage.

Over-pour: The extra amount of concrete placed in a panel beyond the theo-retical panel volume.

P

Panel: Section of a slurry wall that is concreted as a single unit. The panelmay be linear, T-shaped, L-shaped, or other plan configuration.

pcf: Pounds per square foot. Imperial unit of pressure.

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Pipe Sleeve: Insert in wall intended to permit the passage of a pipe throughthe wall.

Pipe Extractor: See End Stop Extractor.

pH: Measure of the alkalinity or acidity of a liquid using a numeric scale setwith 7.0 as neutral, less than 7.0 indicating acidity and greater than 7.0 indi-cating alkalinity.

Plastic Concrete: Concrete consisting of cement, bentonite, aggregates,additives and water intended to provide minimal strength, a low modulus ofelasticity and high strain prior to failure.

Pony Beam: Short waler beam placed across a panel joint intended to sup-port two panels from one point of lateral support.

Porcupine Plate: Steel plate provided with numerous steel studs, straps orbars welded to the plate intended to be embedded in the wall to provide shearor tensile capacity to a connection to the wall.

Post-tensioned Wall: Wall, which derives its primary strength by the applica-tion of longitudinal compression force by tensioning high strength strandsembedded in the wall after the concrete hardens.

Precast Wall: Wall constructed by insertion and positioning of precast con-crete panels into a self-hardening slurry.

Preload: Application to the wall of all or part of a predetermined brace oranchor support load.

Pre-stress: See Preload.

Primary Panel: Panel constructed with end forming devices at both ends.

psi: Pounds per square inch. Imperial unit of pressure.

R

Raker: Sloping brace, which provides lateral support to a wall by transferringforces against a footing or other structural element within the excavation.

Reinforced Concrete Wall: Wall whose primary strength is derived from areinforcing steel cage.

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Reinforcement: Addition of steel to the concrete to provide tensile or bendingstrength.

Reverse Circulation: Method of removing excavation spoil by airlift or pumpand pipe.

Reverse Circulation Drill: Hollow stem chisel with provision to draw ben-tonite slurry and drill cuttings up the stem during drilling.

Rotary Drill: Rotary grinding and cutting device primarily used to fracture orsoften rock.

S

Sand Cone: Calibrated device used to measure percentage of sand by vol-ume suspended in slurry.

Sand Content: Percentage of sand by volume suspended in a slurry fluid.

Secondary Panel: Panel cast against previously concreted panels.

Shoulder Pipe: See End Pipe.

Shop Drawing: Detailed drawing expanding on information shown on designdrawing. Work can be constructed from this drawing.

Shotcrete: mixture of cement, aggregates, additives and water applied underpressure by a spray technique.

Slope Indicator Tube: Pipe device installed vertically in the wall or adjacentground used to guide a slope-measuring device (inclinometer), which meas-ures wall or ground movement.

Slump: Measure of workability of fresh concrete.

Slurry: A mixture of water and clay (bentonite or mineral clay) or polymer incolloidal suspension.

Slurry Specialist: Individual trained and experienced in the mixing, cleaningand use of bentonite slurries as well as all operations necessary to properlyconstruct a slurry wall.

Slurry Trench: An excavation filled with bentonite slurry. Also, a trench back-filled with blended “impervious” soils or cement bentonite.

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Slurry Wall: Concrete wall constructed below ground using slurry to supportthe sidewalls of the excavation.

Socket: Embedment of the wall into a bearing and/or impervious strata.

Soldier Beam: A steel beam or pile section installed vertically into the wall toact as an end stop device or structural reinforcing for a panel. Also, called a“Soldier Pile”.

Soldier Beam and Tremie Concrete Panel: A type of reinforced panel withbeam sections installed vertically into the wall. Also, called “SPTC” type ofwall panel.

Spacer: Device attached to the face of the cage to position the cage in theexcavation and provide the required concrete cover.

Specific Gravity: Ratio of weight of a unit volume of bentonite slurry to a unitvolume of water.

Stabilizing Fluid: Slurry used to support the sidewalls of a slurry trench exca-vation.

Starter Walls: See Guide Walls.

Steel Beam and Concrete Lagging Wall: Wall whose primary strength isderived from vertical steel beams at ends of panel, which serve as stop endsand waterstops. Also, called SPTC panel wall.

Stop End Joint: See End Pipe.

Strut: See Brace.

T

Temporary Wall: Wall used primarily to provide soil and water retention dur-ing construction and not utilized in the permanent construction.

Thixotropy: The property exhibited by a slurry gel that becomes viscouswhen undisturbed and loses viscosity when stirred or agitated.

Tieback: Anchor used to lateral support for a slurry wall panel.

Tieback Sleeve: See Tieback Trumpet.

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Tieback Trumpet: Device cast into the wall intended to permit the installationof a tieback through the wall and the transfer of the tieback load to the wall.

Tolerance: Allowed variation from the design location of the wall.

Top-down Method: Method of constructing a structure from grade downward,constructing the roof and/or floor slabs of the structure in stages with excava-tion proceeding below the slabs. The slabs provide both temporary and per-manent lateral support of the wall.

Tremie Concrete: Concrete placed by the tremie method.

Tremie Method: Utilizes the displacement of a fluid by placement of concretethrough one or more supply pipes, which is kept immersed in fresh concreteso that the rising concrete from the bottom displaces the fluid without washingout the cement content.

Tremie Pipe: Pipe through which tremie concrete is lowered to the bottom ofthe slurry filled panel.

Tremie Plug: Device placed at the bottom of the tremie pipe intended to min-imize mixing of the concrete and slurry at the start of the concrete operation.

Trench Cutter: See Hydromill Excavator.

U

Under the Roof method: See Top-down Method.

Updown Method: Use of the top-down method to excavate the basementwhile simultaneously constructing the superstructure.

V

Viscosity: Measure of shear strength of a liquid.

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W

Wale: Structural member installed at the face of the wall to transfer loads fromthe wall to braces.

Water to Cementitious Materials Ratio: The ratio of the weight of mix waterto the weight of cementitious elements (cement and fly ash).

Watertight Wall: Wall exhibiting a surface free of running water. Patches ofmoisture or beads of water [like beads of sweat] may be evident, but free flow-ing water is not present throughout the wall surface.

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PART IV FIGURES

Figure 1 - Classification of Panels ..........................................................50

Figure 2 - Slurry Wall Panel Configurations ...........................................51

Figure 3 - Types of Panel Joints .............................................................52

Figure 4 - Types of Clamshell Buckets ...................................................53

Figure 5 - Slurry Excavation Operations.................................................54

Figure 6 - Cleanup with Sand Separating Unit .......................................55

Figure 7 - Phases of Slurry Wall Construction........................................56

Figure 8 - Slurry Wall Inspection Report Form .......................................57

Figure 9 - Slurry Fluid Test Report Form ................................................58

Figure 10 - Tremie Concrete Inspection Report Form............................59

Figure 11 - Major Types of Slurry Wall Construction and Applications...60

Figure 12 - Typical Guide Wall Construction ..........................................61

Figure 13 - Guide Wall Constructed in a Prepared Trench ....................62

Figure 14 - Slurry Wall Tolerances..........................................................63

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50

Figure 1: Classification of Panels

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Figure 2: Slurry Wall Panel Configurations

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Figure 3: Types of Panel Joints

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Figure 4: Types of Clamshell Buckets

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Figure 5: Slurry Excavation Operations

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Figure 6: Cleanup with Sand Separating Unit

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Figure 7: Phases of Slurry Wall Construction

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Figure 8: Slurry Wall Inspection Report Form

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Figure 9: Slurry Fluid Test Report Form

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Figure 10: Tremie Concrete Inspection Report Form

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Figure 11: Major Types of Slurry Wall Construction and Applications

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Figure 12: Typical Guide Wall Construction

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Figure 13: Guide Wall Constructed in a Prepared Trench

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Figure 14: Slurry Wall Tolerances

PART V ADDITIONAL INFORMATION

REFERENCES

1. Ressi di Cervia, A.L.,“History of Slurry Wall Construction”, Slurry Walls:Design, Construction and Quality Control, STP 1129, American Societyfor Testing and Materials, Philadelphia, PA (1992).

2. Rodio-Italy, Company publication on geotechnical work experience,AGV-Vicenza-Mondado Group, Italy (October 1986).

3. Tamaro, G.J.,”Load Bearing Elements Constructed Using BentoniteSlurry Techniques”, Notes of the Met Section ASCE Seminar,Foundation Problems in the New York Metropolitan Area (Nov. 3-4,1987).

4. Hooks, J. M. et al, “A Report on the Design and Construction ofDiaphragm Walls in Western Europe”, Federal Highway Administration,Washington D.C. (December 1980).

5. Sociedad Mexicana de Mecanica de Suelos, A.C., “Capitulo 3 - MurosMilan,” Manual de Construccion Geotecnia I, Mexico D.F. (2002).

6. Edgerton, W. W., “Site Investigations: a Guide,” Civil EngineeringMagazine, Reston, VA (June 1998).

7. Tamaro, G.J. and Poletto, R.J., “Slurry Walls- Construction QualityControl”, Slurry Walls: Design, Construction and Quality Control, ASTMSTP 1129, American Society for Testing and Materials, Philadelphia, PA(1992).

8. Rosenvinge, IV, T. and Tamaro, G. J., “Chapter 9: Caissons and SlurryWall Construction”, Field Inspection Handbook”, ed. D.S. Brock, et al,2nd ed., McGraw-Hill, New York (1995).

9. Poletto, R. J. and Good, D. R., “Slurry Walls and Slurry Trenches-Construction Quality Control”, International Containment TechnologyConference Proceedings, FL (Feb. 9-12, 1997).

10. Puller, M. “The Waterproofness of Structural Diaphragm Walls,” Proc.Institute of Civil Engineers - Geotechnical Engineering, Great Britain(Jan. 1994).

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BIBLIOGRAPHY

1. American Petroleum Institute, “Recommended Practice-StandardProcedure for Field Testing Oil-Based Drilling Fluids”, API 13B-2,Washington DC (1990).

2. American Petroleum Institute, “Specification for Drilling-Fluid Materials”,API Specification 13, Washington DC (1990).

3. ASCE, “Slurry Wall Construction for BART Subway Stations”, Preprintsof the ASCE National Meeting on Structural Engineering, Pittsburgh, PA(1968).

4. ASCE, “Design and Performance of Earth Retaining Structures”, SpecialPublication 25, Proceedings of an ASCE Conference, Cornell University,Ithaca, NY (June 1990).

5. Becker, J.M. and Haley, M.X., “Up/Down Construction”, Design andPerformance of Earth Retaining Structures, Proceedings of GeotechnicalEngineering Division, Cornell University, Ithaca, NY (1990).

6. Braun, W.M., “Post-Tensioned Diaphragm Walls in Italy”, ConcreteConstruction, New York (April 1972).

7. Boyes, R.G.H. “Structural and Cut-Off Diaphragm Walls,” Wiley, NewYork (1975).

8. British Standards Institute, “Execution of Special Geotechnical Work-Diaphragm Walls”, Document 94/106168, London (1994).

9. Canadian Geotechnical Society, “Canadian Foundation EngineeringManual”, 2nd ed., Ottawa (1985).

10. Catalano, N., et al. “Post-Tensioned Diaphragm Wall T-Panel for Large

Unbraced Excavation Spans,” Proceedings of the 19th AnnualConference and Meeting of the Deep Foundation Institute, Boston, MA(October 3-5, 1994).

11. Clough, G.W., Performance of Tied-back Walls, “Proceedings of theASCE Specialty Conference on Performance of Earth and EarthSupported Structures”, Vol. 3, Lafayette, IN (1972).

12. Clough, G.W., “Proceedings of the Short Course – Seminar on Analysisand Design of Building Foundation”, Deep Excavations and RetainingStructures, Bethlehem, PA (1975).

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13. Clough, G.W. and Schmidt, B., “Design and Performance of Excavationand Tunnels in Soft Clay”, Soft Clay Engineering, Elsevier ScientificPublishing Co., Amsterdam (1981).

14. Clough, G.W. and Buchignani A.L., “Slurry Walls in the San FranciscoBay Area”, ASCE reprint (1981).

15. Cunningham, J.A. and Fernandez, J.I., “Performance of Two Slurry WallSystems in Chicago”, Proceedings of the Specialty Conference on thePerformance of Earth and Earth Supported Structures, ASCE (1972).

16. Federal Highway Administration, “Proceedings from the Symposium onDesign and Construction of Slurry Walls as Part of PermanentStructures,” Washington DC (March 1980).

17. Gill, S. A. “Applications of Slurry Walls in Civil Engineering Projects”,ASCE Convention Preprint 3355, Chicago, IL (October 1978).

18. Goldberg, A.T., Jaworski, W., E. and Gordon M.D., Federal HighwayAdministration Reports FHWA RD-75-128, FHWA-RD-75-129, FHWA-RD-75-130, National Technical Information Service (1976).

19. Huder, J., “Stability of Bentonite Slurry Trenches with Some Experiencein Swiss Practice”, Proceedings of the Fifth European Conference onSoil Mechanics and Foundation Engineering, Vol. 1, Madrid (1972).

20. Institute of Civil Engineers, “Diaphragm Walls and Anchorages,”Proceedings of the 1974 Conference of the Institution of Civil Engineers,London (1975).

21. Institute of Civil Engineers, “A Review of Diaphragm Walls, A Discussionof Diaphragm Walls and Anchorages,” Institution of Civil Engineers,London (1977).

22. Kapp, M.S., “Slurry Trench Construction for Basement Wall of WorldTrade Center”, Civil Engineering, ASCE (1969).

23. Kerr, W. and Tamaro, G.J., “Diaphragm Walls – Update on Design andPerformance”, Earth Retaining Structures (1988).

24. Kirmani M. and Highfill, S., “Design and Construction of the CircularCofferdam for Ventilation Building No. 6 at the Ted Williams Tunnel,”Civil Engineering Practice, (Spring-Summer 1996).

25. Konstantakos, D.C., “Measured Performance of Slurry Walls”, M.S.Thesis, Department of Civil and Environmental Engineering, MIT,Cambridge, MA (2000).

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26. Konstantakos, D.C., Whittle A.J., et al, “Control of Ground Movementsfor a Multi-level Anchored, Diaphragm Wall during Excavation,”

Proceedings of the 5th Int. Conference on Case Histories in New YorkGeotechnical Engineering, (2004).

27. Lambe, T.W., “Predicted Performance of Braced Excavations”,Proceedings of the ASCE Specialty Conference on Performance ofEarth and Earth Supported Structures, Vol. 3, Lafayette, IN (1972).

28. Littlejohn, G.S. and MacFarlane, I.M., “Case History of Multi-tiedDiaphragm Walls”, Proceedings of the Conference on Diaphragm Wallsand Anchorages, London (1975).

29. Millet, R.A. and Perez, J.Y., “Current USA Practice Slurry WallSpecifications”, Journal of the Geotechnical Engineering Division, ASCEVol. 107, (Aug. 1981).

30. NAVFAC, “Design Manual 7.1 – Soil Mechanics”, Department of Navy,Naval Facilities Engineering Command, Washington, DC (1982).

31. NAVFAC, “Design Manual 7.2 – Foundation and Earth Structures”,Department of Navy, Naval Facilities Engineering Command,Washington, DC (1982).

32. O’Rourke, T.D., “Ground Movements Caused by Braced Excavations”,Journal of Geotechnical Engineering, ASCE Vol. 107 (1981).

33. Paniagua Espinosa, W., Paniagua, Zavala, W.I. and Valle, J.A.,“Construction of Precast Walls in the Tramo Cola –Garibald Line 8 of theMetro”, 2nd Symposium of Construction, SMMS, Mexico (1994).

34. Poletto, R.J., “Slurry Wall Design,” University of Wisconsin-MilwaukeeSeminar on Slurry Walls and Slurry Trenches, Arlington, VA (1999).

35. Rosenberg, P., St. Arnaud, G., et al, “Design, Construction andPerformance of a Slurry Trench Wall next to Foundation”, CanadianGeotechnical Journal, Vol. 14 (1977).

36. Santarelli, G. and Ratay R.T., “Handbook of Temporary Structures inConstruction”, Chapter 9, 2nd ed., McGraw-Hill, New York (1996).

37. Saxena, S.K., “Measured Performances of a Rigid Concrete Wall at theWorld Trade Center”, Proceedings Conference on Diaphragm Walls andAnchorages, Institution of Civil Engineers, London (1974).

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38. Sen. K. K., Alostaz, Y., et al, “Support of Deep Excavation in Soft Clay: A

Case History Study,” Proceedings 5th Int. Conference on Case Historiesin Geot. Engr., New York (2004).

39. Tallard G., “New Trenching Method Using Synthetic Bio-Polymers”,Slurry Walls: Design, Construction and Quality Control, STP 1129,American Society for Testing and Materials, Philadelphia, PA (1992).

40. Tamaro, G.J. and Gould, J.P., “Analysis and Design of Cast In-situWalls”, Retaining Structures, Institution of Civil Engineers, London(1993).

41. Tamaro, G.J., “Slurry Wall Design and Construction”, Design andPerformance of Earth Retaining Structures, ASCE Conference, CornellUniversity, Ithaca, NY (1990).

42. Tamaro, G.J., “Recovery Efforts at the World Trade Center Bathtub”,Proceedings of the 9th Int. Conference on Piling and Deep Foundations,Nice, France (2002).

43. Winter, E.W., Nordmark, T.S. and Tallard, G., “Slurry Wall PerformanceAdjacent to Historic Church”, Slurry Walls: Design, Construction andQuality Control, STP 1129, American Society for Testing and Materials,Philadelphia, PA (1992).

44. Xanthakos, P., “Slurry Walls”, 1st Ed., McGraw-Hill, New York (1979).

45. Xanthakos, P., “Slurry Walls as Structure Systems”, 2nd ed., McGraw-Hill, New York (1994).

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METRIC CONVERSION TABLE

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PART VI PROJECT LIST

Slurry Wall Project List Parameters

Locations:North America only, separate groups by: 50 US States, Boston, New YorkCity and Washington DC

Method/Type:SW - Conventional panel walls constructed with end stop jointsSPTC - Beam Wall systems with concrete considered as laggingPT - Post-tensioned WallsPRE - Precast WallsLBE - Load Bearing Elements or BarrettesTB - Anchored Walls with soil or rock tiebacks.TD - Top-down method of construction usedSH - Shaft Construction used

Year:Date of start of slurry wall construction

Width:Maximum panel depth, in feet

Depth:Maximum panel depth, in feet

Area:Plan length multiplied by wall depth, in square feet

Description:Brief description of project or significant feature of construction, e.g. excavation support wall, permanent wall, shaft wall, etc.

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