Allan Block Retaining Walls - Spec Book

Inside this issue:Product Standards.............................................. 3

Installation Specifications.................................. 5

Water Management............................................ 7

ASTM Standards................................................. 9

Design, Construction and Inspection Check Lists........................................ 11

Design Details..................................................... 13

Water ManagementDetails.................................................................. 14

Geogrid Details................................................... 15

Fencing Applications.......................................... 16

Miscellaneous Details......................................... 17

Design Methods................................................. 19

Allowable ConstructionTolerances........................................................... 20

Geogrid Reinforcement Specifications .................................................... 21

List of Tables:Table 1: Embankment Protection Fabric Specifications ...................8

Table 2: Strength and Absorption Requirements (ASTM)................9

Table 3: Geogrid Manufacturers Testing Results ..............................21

List of Figures:Figure 1: AB Unit - Approximate Dimensions....... 3

Figure 2: Gravity Wall Consolidation Zone............4

Figure 3: Geogrid Wall Consolidation Zone...........6

Figure 4: Surface Water Management................... 7

Figure 5: Construction Water Management...........7

Figure 6A: Internal Blanket......................................8

Figure 6B: Internal Blanket and Chimney Drain....8

Figure 7: Freeze-Thaw Testing............................. ..10

Figure 8: Global Stability.........................................11

Table of Contents

Figure 9: Elevation View.......................................... 11

Figure 10: Wall Site Components........................... 11

Figure 11: Typical Reinforcement Configurations..12

Figure 12: Wall Design Envelope............................ 12

Figure 13: Vertical Control....................................... 20

Figure 14: Differential Settlements......................... 20

Figure 15: Horizontal Control..................................20

Figure 16: Rotation...................................................20

Forth Edition

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Allan Block® Corporation:

A leader in segmental retaining wall design

The following pages will provide assistance to abroad range of professional retaining wall designers.This technical specification manual will allow a walldesigner to source and reference specific informationfor use in developing project documents. Includedare: product standards, installation and water man-agement procedures, design details, industry stan-dards, allowable construction tolerances, projectdesign checklist, project installation checklist, projectinspection checklist, reference design methods, andgeogrid reinforcement options.

The goal is to provide formatted specification sheetsthat summarize information published by Allan Blockand other relevant publications, as well as provide acomprehensive document for most applicationswhich utilize mortarless concrete block as a compo-nent of a segmental retaining wall.

Answering the question:Can segmental retaining walls satisfy the requirements of my project?

Segmental Retaining Walls (SRW’s) have evolved frombeing used in garden and landscape applications in the80’s and 90’s, to now having found their way into com-mercial projects, roadway sites, and major industrialapplications. With estimates of over 200 million AllanBlocks installed worldwide, mortarless segmentalretaining walls have proven their value and durability inthe construction marketplace.

Projects range from walls up to 50 ft (15.2 m) in heightto miles of walls used in roadway, water and otherapplications. The flexible nature of the system hasproven to eliminate the need for frost footings in north-ern climates, provide additional drainage in tropicalareas, and allow for additional flexibility in earthquakeplagued sections of the world. In short, there are veryfew site problems that cannot find a cost effective solu-tion using Allan Block Retaining Wall Products.

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The document focuses on composite structures built bycombining an Allan Block facing unit with a reinforcedsoil mass, and appropriate drainage details. Othermethods of reinforcement will be illustrated in theDesign Detail portion of this publication, but not pre-sented in great detail. The intent of this publication isto assist the local wall design engineer, but not limittheir flexibility for any given design situation.

The specifications shown here as well as the detailedAutocad drawings are available for download on ourwebsite at allanblock.com.

AllanBlock providesSiteSolutions™

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Specification Guidelines: Allan BlockModular Retaining Wall Systems

The following specifications provide Allan Block Corporation'stypical requirements and recommendations. At the engineerof record's discretion these specifications may be revised toaccommodate site specific design requirements.

SECTION 1PART 1: GENERAL1.1 Scope

Work includes furnishing and installing modular concreteblock retaining wall units to the lines and grades designatedon the construction drawings and as specified herein.

1.2 Applicable Sections of Related WorkGeogrid Wall Reinforcement (see Section 2, Page 5)

1.3 Reference StandardsA. ASTM C1372 Standard Specification for Segmental

Retaining Wall Units.B. ASTM C1262 Evaluating the Freeze thaw Durability of

Manufactured CMU’s and Related concrete UnitsC. ASTM D698 Moisture Density Relationship for Soils,

Standard MethodD. ASTM D422 Gradation of SoilsE. ASTM C140 Sample and Testing concrete Masonry Units

1.4 Delivery, Storage, and HandlingA. Contractor shall check the materials upon delivery to assure

proper material has been received.B. Contractor shall prevent excessive mud, cementitious material,

and like construction debris from coming in contact with thematerials.

C. Contractor shall protect the materials from damage. Damagedmaterial shall not be incorporated in the project (ASTMC1372).

PART 2: MATERIALS2.1 Modular Wall Units

A. Wall units shall beAllan BlockRetaining Wallunits as producedby a licensedmanufacturer.

B. Wall units shallhave minimum 28day compressivestrength of 3000 psi (20.7 MPa) in accordance with ASTM C1372.The concrete units shall have adequate freeze-thaw protectionwith an average absorption rate in accordance with ASTM C1372or an average absorption rate of 7.5 lb/ft3 (120 kg/m3) for northernclimates and 10 lb/ft3 (160 kg/m3) for southern climates.

C. Exterior dimensions shall be uniform and consistent. Maximumdimensional deviations on the height of any two units shall be0.125 in. (3 mm).

D. Wall units shall provide a minimum of 110 lbs total weight persquare foot of wall face area (555 kg/m²). Fill contained withinthe units may be considered 80% effective weight.

E. Exterior face shall be textured. Color as specified by owner.3

Allan Block Product Standards

2.2 Wall RockA. Material must be well-graded compactible aggregate, 0.25

in. to 1.5 in., (6 mm - 38 mm) with no more than 10% pass-ing the #200 sieve. (ASTM D422)

B. Material behind and within the blocks may be the same material.

2.3 Infill Soil A. Infill material shall be site excavated soils when approved by

the on-site soils engineer unless otherwise specified in thedrawings. Unsuitable soils for backfill (heavy clays or organicsoils) shall not be used in the reinforced soil mass. Finegrained cohesive soils (�<31 ) may be used in wall construc-tion, but additional backfilling, compaction and water man-agement efforts are required. Poorly graded sands, expansiveclays and/or soils with a plasticity index (PI) >20 or a liquidlimit (LL) >40 should not be used in wall construction.

B. The infill soil used must meet or exceed the designed fric-tion angle and description noted on the design cross sec-tions, and must be free of debris and consist of one of thefollowing inorganic USCS soil types: GP, GW, SW, SP meet-ing the following gradation as determined in accordancewith ASTM D422.

C. Where additional fill is required, contractor shall submit sam-ple and specifications to the wall design engineer or the on-site soils engineer for approval and the approving engineermust certify that the soils proposed for use has propertiesmeeting or exceeding original design standards.

PART 3: WALL CONSTRUCTION3.1 Excavation

A. Contractor shall excavate to the lines and grades shown onthe construction drawings. Contractor shall use caution not toover-excavate beyond the lines shown, or to disturb the baseelevations beyond those shown.

B. Contractor shall verify locations of existing structures and utili-ties prior to excavation. Contractor shall ensure all surroundingstructures are protected from the effects of wall excavation.

3.2 Foundation Soil PreparationA. Foundation soil shall be defined as any soils located

beneath a wall.B. Foundation soil shall be excavated as dimensioned on the

plans and compacted to a minimum of 95% of StandardProctor (ASTM D698) prior to placement of the base material.

C. Foundation soil shall be examined by the on-site soils engineer toensure that the actual foundation soil strength meets or exceedsassumed design strength. Soil not meeting the required strengthshall be removed and replaced with acceptable material.

3.3 BaseA. The base material shall be the same as the Wall Rock material

(Section 2.2) or a low permeable granular material.

B. Base material shall be placed as shown on the construction draw-ing. Top of base shall be located to allow bottom wall units to beburied to proper depths as per wall heights and specifications.

Figure 1:Standard AB Unit -ApproximateDimensions

Sieve Size Percent Passing4 inch 100 - 75No. 4 100 - 20No. 40 0 - 60

No. 200 0 - 35

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C. Base material shall be installed on undisturbed native soils orsuitable replacement fills compacted to a minimum of 95%Standard Proctor (ASTM D698).

D. Base shall be compacted at 95% Standard Proctor (ASTM D698) toprovide a level hard surface on which to place the first course ofblocks. The base shall be constructed to ensure proper wall embed-ment and the final elevation shown on the plans. Well-graded sandcan be used to smooth the top 1/2 in. (13 mm) on the base material.

E. Base material shall be a 4 in. (100 mm) minimum depth forwalls under 4 ft (1.2 m) and a 6 in. (150 mm) minimum depth forwalls over 4 ft (1.2 m).

3.4 Unit InstallationA. The first course of wall units shall be placed on the prepared

base per the manufacturers recommendations. The units shallbe checked for level and alignment as they are placed.

B. Ensure that units are in full contact with base. Proper care shallbe taken to develop straight lines and smooth curves on basecourse as per wall layout.

C. Fill all cores and cavities and a minimum of 12 in. (300 mm)behind the base course with wall rock. Use infill soils behindthe wall rock and approved soils in front of the base course tofirmly lock in place. Check again for level and alignment. Usea plate compactor to consolidate the area behind the basecourse. All excess material shall be swept from top of units.

D. Install next course of wall units on top of base course. Positionblocks to be offset from seams of blocks below. Perfect "run-ning bond" is not essential, but a 3 in. (75 mm) minimum offsetis recommended. Check each block for proper alignment andlevel. Fill all cavities in and around wall units and to a minimumof 12 in. (300 mm) depth behind block with wall rock. For tallerwall application the depth of wall rock behind the block shouldbe increased; walls from 15 ft (4.57 m) to 25 ft (7.62 m) shouldhave a minimum of 2 ft (0.61 m) and walls above 25ft (7.62 m)should have a minimum of 3 ft (0.9 m). Spread infill soil in uni-form lifts not exceeding 8 in. (200 mm) in uncompacted thick-ness and compact to 95% of Standard Proctor (ASTM D698)behind the consolidation zone.

E. The consolidation zone shall be defined as 3 ft (0.9 m) behindthe wall. Compaction within the consolidation zone shall beaccomplished by using a hand operated plate compactor andshall begin by running the plate compactor directly on the blockand then compacting in parallel paths from the wall face until

the entire consolidation zone has been compacted. A minimumof two passes of the plate compactor are required with maxi-mum lifts of 8 in. (200 mm). Expansive or fine-grained soilsmay require additional compaction passes and/or specific com-paction equipment such as a sheepsfoot roller. Maximum lifts of 4 inches (100 mm) may be required to achieve adequate compaction within the consolidation zone. Employ methods using lightweight

compaction equipment that will not disrupt thestability or batter of the wall. Final compactionrequirements in the consolidation zone shall beestablished by the engineer of record.

F. Install each subsequent course in like manner. Repeat procedure tothe extent of wall height.

G. As with any construction work, some deviation from constructiondrawing alignments will occur. Variability in construction of SRWs isapproximately equal to that of cast-in-place concrete retaining walls.As opposed to cast-in-place concrete walls, alignment of SRWs canbe simply corrected or modified during construction. Based uponexamination of numerous completed SRWs, the following recom-mended minimum tolerances can be achieved with good construc-tion techniques. Refer to Page 20.

Vertical Control - ±1.25 in. (32 mm) max. over 10 ft (3 m) distanceHorizontal Location Control - straight lines ±1.25 in. (32 mm) over a 10 ft (3 m) distance.Rotation - from established plan wall batter : 2.0°Bulging - 1.0 in. (25 mm) over a 10 ft (3.0 m) distance

3.5 Additional Construction NotesA. When one wall branches into two terraced walls, it is important to

note that the soil behind the lower wall is also the foundation soilbeneath the upper wall. This soil shall be compacted to a minimumof 95% of Standard Proctor (ASTM D698) prior to placement of thebase material. Achieving proper compaction in the soil beneath anupper terrace prevents settlement and deformation of the upper wall.One way is to replace the soil with wall rock and compact in 8 in. (200mm) lifts. When using on-site soils, compact in maximum lifts of 4 in.(100 mm) or as required to achieve specified compaction.

B. Filter fabric use is not suggested for use with cohesive soils. Clogging ofsuch fabric creates unacceptable hydrostatic pressures in soil reinforcedstructures. When filtration is deemed necessary in cohesive soils, use athree dimensional filtration system of clean sand or filtration aggregate.

C. Embankment protection fabric is used to stabilize rip rap and foun-dation soils in water applications and to separate infill materials fromthe retained soils. This fabric should permit the passage of fines topreclude clogging of the material. Embankment protection fabricshall be a high strength polypropylene monofilament materialdesigned to meet or exceed typical Corps of Engineers plastic filterfabric specifications (CW-02215); stabilized against ultraviolet (UV)degradation and typically exceeding the values in Table 1, page 8.

D. Water management is of extreme concern during and after construc-tion. Steps must be taken to ensure that drain pipes are properlyinstalled and vented to daylight and a grading plan has been devel-oped that routes water away from the retaining wall location. Sitewater management is required both during construction of the walland after completion of construction.

Consult the Allan Block Engineering Department for details at 800-899-5309. A specification subject to change without notice, thiswas last updated on 06/14/2010.

Figure 2: Consolidation Zone - Gravity Wall

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Allan Block Installation Specifications

PART 3: WALL CONSTRUCTION3.1 Foundation Soil Preparation

A. Foundation soil shall be excavated to the lines andgrades as shown on the construction drawings, or asdirected by the on-site soils engineer.

B. Foundation soil shall be examined by the on-site soilsengineer to assure that the actual foundation soilstrength meets or exceeds assumed design strength.

C. Over-excavated areas shall be filled with compactedbackfill material approved by on-site soils engineer.

D. Contractor shall verify locations of existing structuresand utilities prior to excavation. Contractor shall ensureall surrounding structures are protected from the effectsof wall excavation.

3.2 Wall ConstructionWall construction shall be as specified under Section 1, Part 3, Wall Construction, Page 3.

3.3 Geogrid InstallationA. Install Allan Block wall to designated height of first

geogrid layer. Backfill and compact the wall rock andinfill soil in layers not to exceed 8 in. (200 mm) liftsbehind wall to depth equal to designed grid lengthbefore grid is installed.

B. Cut geogrid to designed embedment length and place ontop of Allan Block to back edge of lip. Extend away fromwall approximately 3% above horizontal on compactedinfill soils.

C. Lay geogrid at the proper elevation and orientationsshown on the construction drawings or as directed bythe wall design engineer.

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Specification Guidelines: GeogridReinforcement Systems

The following specifications provide Allan Block Corporation'stypical requirements and recommendations. At the engineerof record's discretion these specifications may be revised toaccommodate site specific design requirements.

SECTION 2PART 1: GENERAL1.1 Scope

Work includes furnishings and installing geogrid reinforce-ment, wall block, and backfill to the lines and grades desig-nated on the construction drawings and as specified herein.

1.2 Applicable Section of Related WorkSection 1: Allan Block Modular Retaining Wall Systems.(see Section 1, page 3)

1.3 Reference StandardsSee specific geogrid manufacturers reference standards.

Additional Standards:A. ASTM D4595 - Tensile Properties of Geotextiles by the

Wide-Width Strip MethodB. ASTM D5262 - Test Method for Evaluating the Unconfined

Creep Behavior of GeogridsC. ASTM D6638 Grid Connection Strength (SRW-U1)D. ASTM D6916 SRW Block Shear Strength (SRW-U2)E. GRI-GG4 - Grid Long Term Allowable Design Strength (LTADS)F. ASTM D6706 - Grid Pullout of Soil

1.4 Delivery, Storage, and HandlingA. Contractor shall check the geogrid upon delivery to assure

that the proper material has been received.B. Geogrid shall be stored above -10 F (-23 C).C. Contractor shall prevent excessive mud, cementitious

material, or other foreign materials from coming in contactwith the geogrid material.

PART 2: MATERIALS2.1 Definitions

A. Geogrid products shall be of high density polyethylene orpolyester yarns encapsulated in a protective coating specif-ically fabricated for use as a soil reinforcement material.

B. Concrete retaining wall units are as detailed on the draw-ings and shall be Allan Block Retaining Wall Units.

C. Drainage material is free draining granular material asdefined in Section 1, 2.2 Wall Rock, Page 3.

D. Infill soil is the soil used as fill for the reinforced soil mass.E. Foundation soil is the in-situ soil.

2.2 ProductsGeogrid shall be the type as shown on the drawings having theproperty requirements as described within the manufacturersspecifications.

2.3 Acceptable ManufacturersA manufacturer's product shall be approved by the wall designengineer.

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D. Correct orientation of the geogrid shall be verified by thecontractor and on-site soils engineer. Strength directionis typically perpendicular to wall face.

E. Follow manufacturers guidelines for overlap requirements.In curves and corners, layout shall be as specified inDesign Detail 9-12: Using Grid With Corners andCurves, Page 15.

F. Place next course of Allan Block on top of grid and fillblock cores with wall rock to lock in place. Remove slackand folds in grid and stake to hold in place.

G. Adjacent sheets of geogrid shall be butted against eachother at the wall face to achieve 100 percent coverage.

H. Geogrid lengths shall be continuous. Splicing parallelto the wall face is not allowed.

3.4 Fill PlacementA. Infill soil shall be placed in lifts and compacted as specified

under Section 1, Part 3.4, Page 4, Unit Installation.B. Infill soil shall be placed, spread and compacted in such

a manner that minimizes the development of slack ormovement of the geogrid.

C. Only hand-operated compaction equipment shall beallowed within 3 ft (0.9 m) behind the wall. This areashall be defined as the consolidation zone. Compactionin this zone shall begin by running the plate compactordirectly on the block and then compacting in parallelpaths to the wall face until the entire consolidation zonehas been compacted. A minimum of two passes of theplate compactor are required with maximum lifts of 8 in.(200 mm). Section 1, Part 3.4 E, Page 4.

D. When fill is placed and compaction cannotbe defined in terms of Standard ProctorDensity, then compaction shall be performed using ordinarycompaction process and compacted so that no deformationis observed from the compaction equipment or to the satis-faction of the engineer of record or the site soils engineer.

E. Tracked construction equipment shall not be operateddirectly on the geogrid. A minimum fill thickness of 6 in.(150 mm) is required prior to operation of tracked vehiclesover the geogrid. Turning of tracked vehicles should bekept to a minimum to prevent tracks from displacing thefill and damaging the geogrid.

F. Rubber-tired equipment may pass over the geogrid rein-forcement at slow speeds, less than 10 mph (16 Km/h).Sudden braking and sharp turning shall be avoided.

G. The infill soil shall be compacted to achieve 95% StandardProctor (ASTM D698). Compaction tests shall be taken at 3 ft(0.9 m) behind the block and at the back of the reinforcedzone. The frequency shall be as determined by the on-sitesoils engineer or as specified on the plan. Soil tests of theinfill soil shall be submitted to the on-site soils engineer forreview and approval prior to the placement of any material.The contractor is responsible for achieving the specified com-paction requirements. The on-site soils engineer may directthe contractor to remove, correct or amend any soil found notin compliance with these written specifications.

3.5 Special ConsiderationsA. Geogrid can be interrupted by periodic penetration of a

column, pier or footing structure.B. Allan Block walls will accept vertical and horizontal rein-

forcing with rebar and grout.C. If site conditions will not allow geogrid embedment length,

consider the following alternatives:• Masonry Reinforced Walls • Soil Nailing• Increased Wall Batter • Earth Anchors• Double Allan Block Wall • Rock Bolts• No-Fines Concrete See Design Details Page 17 and 18.

D. Allan Block may be used in a wide variety of water applicationsas indicated in Section 3, Part 1.8, Page 8.

Consult the Allan Block Engineering Department for details 800-899-5309. A specification subject to change without notice, thiswas last updated on 03/02/2009.

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Figure 3: Consolidation Zone - Reinforced Zone

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Allan Block Water Management

Specification Guidelines:Water ManagementThe following specifications provide Allan Block Corporation's typ-ical requirements and recommendations. At the engineer ofrecord's discretion these specifications may be revised to accom-modate site specific design requirements.

Section 3 PART 1: GENERAL DRAINAGE1.1 Surface DrainageRainfall or other water sources such as irrigation activities collectedby the ground surface atop the retaining wall can be defined as sur-face water. Retaining wall design shall take into consideration themanagement of this water.

A. At the end of each day’s construction and at final completion,grade the backfill to avoid water accumulation behind the wallor in the reinforced zone.

B. Surface water must not be allowed to pond or be trapped inthe area above the wall or at the toe of the wall.

C. Existing slopes adjacent to retaining wall or slopes createdduring the grading process shall include drainage details sothat surface water will not be allowed to drain over the top ofthe slope face and/or wall. This may require a combination ofberms and surface drainage ditches.

D. Irrigation activities at the site shall be done in a controlled andreasonable manner. If an irrigation system is employed, thedesign engineer or irrigation manufacture shall provide detailsand specification for required equipment to ensure againstover irrigation which could damage the structural integrity ofthe retaining wall system.

E. Surface water that cannot be diverted from the wall must becollected with surface drainage swales and drained laterally inorder to disperse the water around the wall structure.Construction of a typical swale system shall be in accordancewith Design Detail 5: Swales, Page 14.

1.2 GradingThe shaping and recontouring of land in order to prepare it for sitedevelopment is grading. Site grading shall be designed to routewater around the walls.

A. Establish final grade with a positive gradient away from thewall structure. Concentrations of surface water runoff shall bemanaged by providing necessary structures, such as pavedditches, drainage swales, catch basins, etc.

B. Grading designs must divert sources of concentrated surfaceflow, such as parking lots, away from the wall.

1.3 Drainage SystemThe internal drainage systems of the retaining wall can bedescribed as the means of eliminating the buildup of incidental

water which infiltrates the soils behind the wall. Drainage sys-tem design will be a function of the water conditions on the site.Possible drainage facilities include Toe and Heel drainage col-lection pipes and blanket or chimney rock drains or others.Design engineer shall determine the required drainage facilitiesto completely drain the retaining wall structure for each partic-ular site condition.

A. All walls will be constructed with a minimum of 12 in. (300 mm) of wall rock directly behind the wall facing. Thematerial shall meet or exceed the specification for wall rockoutlined in Section 1, 2.2 Wall Rock, Page 3.

B. The drainage collection pipe, drain pipe, shall be a 4 in. (100 mm) perforated or slotted PVC, or corrugated HDPEpipe as approved by engineer of record.

C. All walls will be constructed with a 4 in. (100 mm) diameterdrain pipe placed at the lowest possible elevation within the12 in. (300 mm) of wall rock. This drain pipe is referred to asa toe drain, Section 3, 1.4 Toe Drain, Page 7.

D. Geogrid Reinforced Walls shall be constructed with an additional 4 in. (100 mm) drain pipe at the back bottom of thereinforced soil mass. This drain pipe is referred to as a heeldrain, Section 3, 1.5 Heel Drain, .

1.4 Toe DrainA toe drain pipe should be located at the back of the wall rockbehind the wall as close to the bottom of the wall as allowed whilestill maintaining a positive gradient for drainage to daylight, or astorm water management system. Toe drains are installed for inci-dental water management not as a primary drainage system.

A. For site configurations with bottoms of the base on a levelplane it is recommended that a minimum one percent gra-dient be maintained on the placement of the pipe with out-lets on 50 ft (15 m) centers, or 100 ft (30 m) centers if pipe iscrowned between the outlets. This would provide for a max-imum height above the bottom of the base in a flat configu-ration of no more than 6 in. (150 mm).

B. For rigid drain pipes with drain holes the pipes should bepositioned with the holes located down. Allan Block does notrequire that toe drain pipes be wrapped when installed intobase rock complying with the specified wall rock material.

C. Pipes shall be routed to storm drains where appropriate orthrough or under the wall at low points when the job sitegrading and site layout allows for routing. Appropriatedetails shall be included to prevent pipes from beingcrushed, plugged, or infested with rodents.

D. On sites where the natural drop in grade exceeds the onepercent minimum, drain pipes outlets shall be on 100 foot(30 m) centers maximum. This will provide outlets in theevent that excessive water flow exceeds the capacity of pipeover long stretches.

E. When the drain pipe must be raised to accommodate outletsthrough the wall face, refer to the Design Detail 4:Alternate Drain, Page 14.

Figure 5: Construction Water Management

Figure 4: Surface Water Management

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1.5 Heel DrainThe purpose of the heel drain is to pick up any water thatmigrates from behind the retaining wall structure at the cutand route the water away from the reinforced mass during theconstruction process and for incidental water for the life of thestructure.

A. The piping used at the back of the reinforced mass shallhave a one percent minimum gradient over the length,but it is not critical for it to be positioned at the very bot-tom of the cut. Additionally the entire length of the pipemay be vented at one point and should not be tied intothe toe drain.

B. The pipe may be a rigid pipe with holes at the bottomwith an integral sock encasing the pipe or a corrugatedperforated flexible pipe with a sock to filter out fineswhen required based on soil conditions. For infill soilswith a high percentage of sand and/or gravel the heeldrain pipe does not need to be surrounded by drainagerock. When working with soils containing more than fiftypercent clay, one cubic foot of drainage rock is requiredfor each foot of pipe.

1.6 Ground WaterGround water can be defined as water that occurs within thesoil. It may be present because of surface infiltration or watertable fluctuation. Ground water movement must not beallowed to come in contact with the retaining wall.

A. If water is encountered in the area of the wall duringexcavation or construction, a drainage system (chimney,composite or blanket) must be installed as directed bythe wall design engineer.

B. Standard retaining wall designs do not include hydro-static forces associated with the presence of groundwater. If adequate drainage is not provided the retainingwall design must consider the presence of the water.

C. When non-free draining soils are used in the retainedzone, the incorporation of a chimney and blanket drainshould be added to minimize the water penetration intothe reinforced mass. Refer to Design Detail 6: Chimneyand Blanket Drain, Page 14.

1.7 Concentrated Water SourcesAll collection devices such as roof downspouts, storm sewers,and curb gutters are concentrated water sources. They must bedesigned to accommodate maximum flow rates and to vent out-side of the wall area.

A. All roof downspouts of nearby structures shall be sizedwith adequate capacity to carry storm water from the roofaway from the wall area. They shall be connected to adrainage system in closed pipe and routed around theretaining wall area.

B. Site layout must take into account locations of retainingwall structures and all site drainage paths. Drainage pathsshould always be away from retaining wall structures.

C. Storm sewers and catch basins shall be located away fromretaining wall structures and designed so as not to intro-duce any incidental water into the reinforced soil mass.

D. A path to route storm sewer overflow must be incorporat-ed into the site layout to direct water away from the retain-ing wall structure.

1.8 Water ApplicationRetaining walls constructed in conditions that allow standing ormoving water to come in contact with the wall face are consid-ered water applications. These walls require specific design andconstruction steps to ensure performance.Refer to Design Detail 7 and 8: Water Applications, Page 14.

A. Embankment protection fabric is used to stabilize rip rapand foundation soils in water applications and to separateinfill materials from the retained soils. This fabric shouldpermit the passage of fines to preclude clogging of thematerial. Embankment protection fabric shall be a highstrength polypropylene monofilament material designed tomeet or exceed typical Corps of Engineers plastic filter fabricspecifications (CW-02215); stabilized against ultraviolet (UV)degradation and typically exceeding the values in Table 1.

B. Infill material shall be free draining to meet the site require-ments based on wave action and rapid draw down conditions.

C. Rip rap or alternative products such as “Trilock” may berequired as a toe protector to eliminate scour at the base ofthe wall.

Consult the Allan Block Engineering Department for details 800-899-5309. A specification subject to change without notice, thiswas last updated on 09/01/2007.

Mechanical DeterminationProperty Method

Tensile Strength = 375 lbs (170 kg) ASTM D-4632

Puncture Strength = 145 lbs (66 kg) ASTM D-3787

Equivalent Opening Size (EOS) = 70 CW-02215(U.S. Sieve #)

Mullen Burst = 480 psi (3.3 Mpa) ASTM D-3786

Trapezoidal Tear = 105 lbs (48 kg) ASTM D-4533

Percent Open Area = 4% CW-02215

Permeability = 0.01 cm/sec ASTM D-4491

Table 1: Embankment Protection Fabric Specifications

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Figure 6A: Internal Blanket

Figure 6B: Internal Blanket and Chimney Drain

ASTM C1372 Standard Specifications for Segmental Retaining Wall Units

Specification Guidelines:Product Specifications forSegmental Retaining Wall Units

Section 4 The following summarizes the contents of ASTM C1372 andkey components relevant when specifying modular con-crete block for use in structural retaining wall designs. Acopy of the full standard is available upon request. Thissummary attempts to provide the information which ismost commonly used, but Allan Block does not claim thatall information contained in the standard is represented.

1. Scope1.1 This specification covers dry-cast segmental retaining wall

units of concrete, machine–made from hydraulic cement,water, and suitable mineral aggregates with or without theinclusion of other materials. The units are intended for usein the construction of mortarless segmental retaining walls.

5. Physical Requirements 5.1 At the time of delivery to the work site, the units shall con-

form to the physical requirements of Table 2 when testedin accordance with 8.2.

5.2 Freeze-Thaw Durability — In areas where repeated freezingand thawing under saturated conditions occur, freeze-thawdurability shall be demonstrated by test or by proven fieldperformance that the segmental retaining wall units haveadequate durability for the intended use. When testing isrequired by the specifier to demonstrate freeze-thaw dura-bility, the units shall be tested in accordance with 8.3.

5.2.1 Specimens shall comply with either of the following: (1) the weight loss of each of five test specimens at the con-clusion of 100 cycles shall not exceed 1 % of its initialweight; or (2) the weight loss of each of four of the five testspecimens at the conclusion of 150 cycles shall not exceed1.5 % of its initial weight.

6. Permissible Variations in Dimensions6.1 Overall dimensions for width, height, and length shall

differ by not more than ± 1/8 in. (3.2 mm) from specifiedstandard dimensions.

6.1.1 Dimensional tolerance requirements for width shall bewaived for architectural surfaces.

7. Finish and Appearance7.1 All units shall be sound and free of cracks or other

defects that interfere with the proper placement of theunit or significantly impair the strength or permanenceof the construction. Minor cracks incidental to the usualmethod of manufacture or minor chipping resulting fromcustomary methods of handling in shipment and deliv-ery, are not grounds for rejection.

7.2 Where units are to be used in exposed wall construction,the face or faces that are to be exposed shall not showchips or cracks, not otherwise permitted, or other imper-fections when viewed from a distance of not less than 20 ft(6.1 m) under diffused lighting.

7.2.1 Five percent of a shipment containing chips not largerthan 1 in. (25.4 mm) in any dimension, or cracks notwider than 0.02 in. (0.5 mm) and not longer than 25 %of the nominal height of the unit is permitted.

7.3 The color and texture of units shall be specified by thepurchaser. The finished surface that will be exposed inplace shall conform to an approved sample consistingof not less than four units, representing the range oftexture and color permitted.

8. Sampling and Testing8.1 The purchaser or authorized representative shall be

accorded proper facilities to inspect and sample unitsat the place of manufacture from the lots ready fordelivery.

8.2 Sample and test units for compressive strength, absorp-tion, and dimensional tolerances in accordance with TestMethods ASTM C140.

8.3 When required, sample and test five specimens forfreeze-thaw durability in water in accordance with TestMethod ASTM C1262. Freeze-thaw durability shall bebased on tests of units made with the same materials,concrete mix design, manufacturing process, and curingmethod, conducted not more than 24 months prior todelivery.

9. Compliance9.1 If a sample fails to conform to the specified requirements, the

manufacturer shall be permitted to remove units from theshipment. A new sample shall be selected by the purchaserfrom remaining units from the shipment with a similar con-figuration and dimension and tested at the expense of themanufacturer. If the second sample meets the specifiedrequirements, the remaining portion of the shipment repre-sented by the sample meets the specified requirements. Ifthe second sample fails to meet the specified requirements,the remaining portion of the shipment represented by thesample fails to meet the specified requirements.

Minimum Required Net Average CompressiveStrength, psi (MPa)

Average of 3 units Individual Unit3000 (20.7) 2500 (17.2)

Maximum Water Absorption Requirements, lb/ft3 (kg/m3)

Weight Classification Oven-Dry Density of Concrete lb/ft3 (kg/m3)

Light Weight Medium Weight Normal WeightLess than 105 (1682) to 125 (2002)105 (1682) less than 125 (2002) or more18 (288) 15 (240) 13 (208)

TABLE 2: Strength and Absorption Requirements (ASTM)

9

ASTM C1262 Standard Test Method for Evaluating the Freeze-Thaw Durabilityof Manufactured Concrete Masonry Units and Related Concrete Units

Section 5The following summarizes the contents of ASTM C1262 andkey components of the test methods used to determine rela-tive freeze thaw durability. This does not provide a compari-son to field performance but a systematic approach to testing.A copy of the full standard is available upon request. Thissummary attempts to provide the information which is mostcommonly used, but Allan Block does not claim that all infor-mation contained in the standard is represented.

1. Scope1.1 This test method covers the resistance to freezing and

thawing manufactured concrete masonry and related con-crete units. Units are tested either in water or in a salinesolution depending on the intended use of the units inactual service.

Note 1 — Concrete masonry and related concrete units includeunits such as hollow and solid concrete masonry units, con-crete brick, segmental retaining wall units, concrete pavers,and concrete roof pavers.

4. Significance and Use4.1 The procedure described in this test method is intended to

determine the effects of freezing and thawing on concreteunits in the presence of water or saline solution.

4.2 The procedure is not intended to provide a quantitativemeasure of the length of service that may be expected froma specific type of concrete unit.

6. Sampling6.1 Selection of Test Specimens — Select whole units represen-

tative of the lot from which they are selected. The units shallbe free from visible cracks or structural defects.

6.2 Number of Specimens — Select five units for freezing andthawing tests. If compression and absorption tests are to beperformed on the same set of units in accordance with TestMethods C140, select additional units as required.Specimens (coupons) used for Test Methods C140 tests shallnot be used as specimens for freezing–and–thawing tests.

7. Preparation of Test Specimens7.1 Freezing and Thawing Test Specimens — Test specimens shall

consist of solid coupons saw-cut from full sized units. Do notsaw-cut test specimens from units that have been previous-ly oven-dried. Do not subject test specimens to ovendryingprior to completion of freezing–and–thawing testing.

71.1 One coupon shall be cut from each of the five sampledunits. Using a water-cooled saw, cut the coupon from theexposed surface of the unit as the unit is used in serviceunless the exposed surface is a split, fluted (ribbed), or othernonplanar surface. In the case of a unit with an exposednonplanar surface, cut the coupon from another flat moldedsurface. Immediately following saw-cutting, remove looseparticles and residue from the coupon by rinsing in tapwater and brushing with a soft bristle brush. Do not fullyimmerse coupons in water.

8. Procedure8.1 Specimen Conditioning:8.1.1 After preparation of the freezing–and–thawing test specimens

in accordance with Section 7, place the specimen in the con-10

tainer face down on the specimen supports such that the non-saw-cut surface of the specimen is in contact with the speci-men supports. Add a sufficient amount of water at a tempera-ture of 60 to 80°F (16 to 27°C) to the container to achieve awater depth of 1/2 ± 1/16 in. (13 ± 2 mm). Do not pour waterdirectly onto the specimen. For test specimens being evaluat-ed for freezing–and–thawing durability in saline solutions, usea 3 ± 0.1 % (by weight) sodium chloride saline solution in lieuof water in the container. Seal the container and store on alevel surface in laboratory air as defined in 7.1.2.

8.2 Cyclical Testing:8.2.3 One freezing–and–thawing cycle is defined as a completed

freezing cycle followed by a completed thawing cycle.8.2.4 At 25 ± 5 cycle intervals, remove containers from the test cham-

ber. Open containers to visually inspect the condition of thespecimens and to adjust the water level to comply with 8.1.1.

8.3 Collection of Residue:8.3.1 Weigh to the nearest 0.2 g (0.0005 lb) and record as Wf a filter

paper of high wet strength and smooth surface that has cometo equilibrium temperature with the lab environment. Removea single specimen from its container. Immediately rinse thespecimen with water (if the specimen is tested in saline solu-tion, use saline solution to rinse the specimen) using asqueeze bottle, being careful to collect in the specimen con-tainer the rinse water and all loose particles from the speci-men. Consider any pieces that separated from the specimenas part of the residue. Pour the water (or saline solution) fromthe specimen container through the filter paper to collect theresidue (spall) from the test specimen. Replace the specimenin the container. Using fingertips and a squeeze bottle, removeloose particles from all surfaces of the specimen, again beingcareful to collect all rinse water and loose particles in the spec-imen container. The top surface of the specimen shall not beimmersed in water at anytime and the collected rinse watershall not exceed a depth of 1.2 in. (13 mm) in the container.Remove the specimen from the container, pour the rinse waterthrough the filter paper, and rinse the specimen container untilall residue (spall) in the specimen container is collected on thefilter paper. Rinse the residue from specimens tested in salinesolution three times with water to remove any soluble salt.

9. Calculation and Report9.1 Determine and report the cumulative weight loss of each

residue collection interval expressed in terms of g (lb) and as apercent of the calculated initial weight of the specimen,Winitial, determined in accordance with 8.3.5. Where thecoupon thickness is less than 1.25 in. (32 mm), the percent-age and cumulative weight loss shall be multiplied by a valueequal to the actual thickness in inches (mm) divided by 1.25 in.(32 mm). Report these values for each specimen as well as theaverage of the specimens tested.

Figure 7: Freeze-Thaw Testing

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Wall Design Checklist

To ensure that the basics are covered in your wall designwe have prepared the following wall design checklist. Itmay also be used by someone checking your work to pro-vide an outline for a consistent review process.

Review Wall Design Plans For Special Conditions:

• Site Drainage Layout• Global Stability• Government Regulations• High Water Table• Seismic Design Requirements

Review Wall Design Plans For:• Overall Length of Wall• Station Points• Plan Layout• Elevations• Grades or Slopes Above or Below Walls• Soil Conditions

Retained Soil Friction AngleInfill Soil Friction AngleFoundation Soil Friction AngleCohesion for Foundation SoilSoil Settlement Potential

• Water ManagementAbove GradeBelow GradeExcess Irrigation

• Locations of Catch Basins and Utilities• Compliance to Specifications• Surcharges (live, dead, and location)• Temporary Construction Loads• Snow or Storage Loads• Special Provisions

Design Review:• Grid Length• Grid Spacing• Grid Placed on Consistent Courses• Design Factors of Safety

SlidingOverturningBearingGrid OverstressPullout from SoilPullout from BlockInternal CompoundGlobalSeismic

• Water Management DetailsSurface Water SourcesSubsurface Water SourcesDetails for Low Permeability SoilsLocation and Venting of Toe and Heel Drains

• Overall Quantity EstimatesBlockGridWall Rock

• Construction Details• General Notes and Specifications

Figure 8: Global Stability

Figure 9: Elevation View

Figure 10: Wall Site Components

11

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Construction and Inspection Checklist

Review Construction Details And Procedures:

A. Mark station points for top and bottom of wall elevations andchanges in wall direction.

B. Identify changes in grid lengths, location of grids, and typesof grid to be used.

C. Determine and locate proper base size for each section of wall.

D. Verify that the correct type and color of block has beenordered and delivered to the job.

E. Verify that the foundation soil and retained soil conform todesign requirements.

F. Verify that infill soil meets design standards.

G. Verify that compaction testing will be performed, who isresponsible, at what intervals of locations along the wall,and what coordination will be required.

H. Determine what method will be used to verify constructionmaterials, methods, and sequence of construction. (ie: writ-ten documentation of as built, full time inspector on site,photographic documentation.)

I. Wall contractor is responsible for quality control of wallinstallation per the approved plans. The owner or owner’srepresentative is responsible for engineering and qualityassurance of the project.

We have prepared the following Construction andInspection Checklist to provide a list of items covering thebasics for your retaining wall project. It may also be usedduring the bidding process to ensure that all special provi-sions are complied with. Always check your local buildingcodes, document any changes to the plan in writing andnotify the wall design engineer with any concerns on watermanagement.

Review Wall Design Plans For:

A. Compliance of Site to Latest Site Plan• Does the site plan and wall layout coincide with current

Site Conditions?• Have all slopes above and below the walls been taken into

account on the plans?• Do the section drawings match the topography of the job-

site? • Have site utilities been accounted for?• Are there any recommendations for changes to the site

plans to accommodate the wall?

B. Review of Reported Soil Conditions with On-SiteSoils Engineer

• Are on-site soils consistent with soil parameters used inwall design?

• Does the site show indications of multiple types of soil,and has this been accounted for?

• Is there evidence of landfill areas on site?• Has the owner contracted with a geotechnical engineer-

ing firm for overall / global stability outside of the walldesign envelope (H tall by the greater of 2H or He + Llong)? See Figure 12.

C. Review of Above Grade Water Management withProject Civil Engineer

• Has surface runoff been accounted for in the site design?• Will this site be irrigated?• If storm drains become inoperable where will the water

migrate to?• During renovation of land will temporary drainage be an

issue?

D. Review of Below Grade Water Management withWall Design Engineer and General Contractor

• How and where will drain pipes be installed?• Is it possible to vent drain pipes to daylight?• Is venting to a storm drainage system an option?• Will outlets be located and protected from blockage or

damage?

E. Surcharges• Have all surcharges been accounted for?• During construction are there any temporary surcharges

that should be accounted for?

Figure 11: Typical Reinforcement Configuration

Figure 12: Wall Design Envelope

12

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Design Details

Detail 1: Typical Reinforced Wall Application

Detail 2: Typical Gravity Wall Application Detail 3: Allan Block Plantable Wall

13

The following drawings are for general information and use. They are not to be relied upon for any specific project without beingreviewed by an engineer. They are not to be used for construction. It is the sole responsibility of the user to verify the applica-bility of the drawing to their specific project. The drawings are available for download in .dwg or .pdf format at allanblock.comfor modifications by an engineer to be site specific to a project.

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Detail 7: Taller Height Reinforced Water Applications Detail 8: Low Height Reinforced Water Applications

Detail 5: Swales Detail 6: Chimney and Blanket Drain

14

Detail 4: Alternate Drain

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Design Details

Detail 13: Step Up at Base Course Detail 14: Grouted Connection

Detail 11: Inside Curve Geogrid Overlap Detail 12: Outside Curve Geogrid Overlap

Detail 9: Inside Corner Geogrid Overlap Detail 10: Outside Corner Geogrid Overlap

15allanblock.com


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Detail 19: Wind Bearing Fence or Railing, Option 2 Detail 20: Masonry Parapet

Detail 17: Alternate Fence Footing with SLEEVE-ITFooting System

Detail 18: Wind Bearing Fence or Railing, Option 1

Detail 15: Non-Wind Bearing Fence or Railing, Option 1 Detail 16: Non-Wind Bearing Fence or Railing, Option 2

16

™

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allanblock.com

Design Details

Detail 25: Concrete Collar Storm Water Pipe Outlet, Section and Elevation View

Detail 23: Impact Roadway or Parking Guard Rail Detail 24: No-Fines Concrete

Detail 21: Double Wall Parapet Detail 22: Non-Impact Parking Railing

17


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Detail 30: Allan Block Facing to Soil Nail ReinforcedShotcrete Wall

Detail 31: Allan Block Facing to Earth Anchor Tiebacks

Detail 28: Allan Block Masonry Reinforced Typical Section

Detail 29: Allan Block Veneer Typical Section

Detail 26: Terraced Section Detail 27: Allan Block Double Wall Typical Section

18

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Design Methods

The following information is intended to provide insight intothe basic concepts behind an Allan Block retaining wall design.A complete review of the methodology and the equations maybe found by reviewing the Allan Block Engineering Manual.

Allan Block walls are most often designed and constructed aseither gravity walls or coherent gravity masses, but can be usedin many different types of retaining wall applications;

Gravity Walls are structures that resist the pressures from theretained soil with the weight of the facing. Under optimum condi-tions Allan Block gravity walls may be constructed up to 5.5 ft (1.7 m).

Coherent Gravity Masses act as large composite structures.These structures are a flexible unified mass that resist the forcesfrom the retained soil in the same manner as a simple gravity wall.These composite structures are composed of geogrid reinforcedsoil masses with Allan Block Retaining Walls used as a durable,aesthetically pleasing, facing material.

Other reinforcement options include Tie Back Walls orMasonry Reinforcement. Tie Backs utilize Allan Block as a hardfacing with some type of anchor used to tie back the facing.Designs of this type develop loads at the face and end of theanchor and do not perform as a coherent gravity mass. Masonryreinforcement applications use grout and rebar through thecores of the Allan Block to create a high strength cantilever wall.

Allan Block Corporation has developed several tools to help thedesign engineer through the design process. Available toolsinclude:

Allan Block Engineering Manual — providing detailedcalculations and commentary for the methods and process-es used in the design procedure.

AB Walls 2007™ — a Windows based software design pro-gram that is a tool for the designer and allows configurationa wall structure that is appropriate for the site and applica-tion. This software also allows the designer to calculate crosssections, elevation views, plan views and material estimatesthat are all coordinated and export them to AutoCAD format.

Hand Calculations — a MathCAD based file that containsall of the detailed calculations for the engineer to review aswell as providing the engineer the ability to revise the equa-tions to fit the particular need of the job in process while pro-viding a method to cross check the output of AB Walls 2007™.

The basic elements of the design process require an under-standing of the properties of the soils to be used behind andbelow the retaining wall, terrain changes above or below theretaining structure, surcharges located above the wall, and seis-mic loading if appropriate.

The design calculation process has two categories of stability tobe checked; external stability and internal stability.

External stability analysis applies to the outside of the retainingwall or reinforced mass. The forces exerted on the structure arecalculated by using an equation developed by Coulomb in 1776called active earth pressure. The term “active” refers to the abil-ity of the wall structure to rotate and bend in small incrementswithout adversely affecting the stability. This equation takes

into account the strength of the soil, slope of the backfill, thebatter of the retaining wall, and the effects of the frictionbetween the retained soil and the retaining wall structure.When addressing external stability the engineer will designfor adequate factors of safety with respect to overturning(eccentricity), sliding, bearing capacity, and global stability.

Internal stability applies to forces and reactions within theblocks and geogrid reinforcement. Here a designer will checkfor adequacy in block to reinforcement connection strength,reinforcement pullout from the soil, reinforcement overstressand, Internal Compound Stability (ICS). See the AB EngineeringManual (Chapter 6) for a complete disclosure on ICS calcula-tions. See geogrid reinforcement specifications section for fur-ther explanation of how geogrid works. Refer to Page 21.

Retaining wall designs rely heavily on the site soil properties.At the beginning of the design process a value is assigned tothe soil that numerically describes how much resistance tomovement this soil possesses. This resistance to movement iscalled the internal friction angle (�, PHI). As the internal fric-tion of the soil increases it exerts less force on the retainingwall. Soils that contain high percentages of sands and gravelhave higher friction angles, drain away excess water morereadily, and are easier to use during the construction process.For these reasons soils with sand and gravel are preferredmaterials to use when constructing a reinforced soil structure.

Soils exhibit another property that resists movement calledcohesion, which is typically found in clay soils. Cohesion maybe classified as temporary strength because it depends great-ly on moisture content of the soil, because of this it is not uti-lized in most elements of the design process.

Water pressure is not considered in a typical design. Becausewater adversely affects the strength and weight properties ofsoil within the composite structure, primary considerationshould be given to manage water away from the retaining wallstructure. These structures have been developed to drain awayonly incidental water which may infiltrate the mass during orafter construction. The wall rock and drain pipe are included tokeep the surrounding soil at its optimum moisture content.

A designer must also consider aspects of the retaining wallthat are not solved in calculations. They must address all theelements surrounding the structure and set construction stan-dards. Compaction requirements, geogrid spacing, andgeogrid length are a few of these items to consider. (See AllanBlock Tech Sheet #598 – Designing Balance Into Your RetainingWall Project for further information).

Allan Block products can be used for almost any application.Incorporating these design concepts will help any engineer cre-ate a safe, aesthetically pleasing, and cost effective retaining wall.

F = (0.5)(�)(Ka)(H)2

csc(�) sin (�-�)sin(��w) � sin(��w) sin(��i)

sin(��i)

� = Soil Unit Weight

[ ]Ka =2

19allanblock.com

allanblock.com

Allowable Construction Tolerances

20

Figure 13: Vertical Control

Figure 14: Differential Settlement

Figure 15: Horizontal Control Figure 16: Rotation

Construction Tolerances

To ensure that acceptable work standards are understood duringretaining wall installation, construction tolerances need to beestablished. These construction tolerances should consider thatthe retaining wall is designed to be a flexible structure that tol-erates horizontal and vertical variation. However, too much vari-ation can affect the structural stability of the wall.

To maintain horizontal and vertical control, adjustments maybe required during modular block installation. Even with tightquality control procedures by block manufactures, modularblock units may vary in height. Shimming a maximum of0.125 in. (3 mm) per block is acceptable construction practice.It is recommended that shimming material be asphaltic ornon-degradable products.

Acceptable construction tolerances are illustrated in Figures13 thru 16.

Differential Settlement

Foundation settlements must be estimated with great care for build-ings, bridges, towers, power plants, and similar high-cost structures.For structures such as fills, earth dams, levees, and retaining walls agreater margin of error in settlements can usually be tolerated. Theconstruction method of placing the dry-stacked mortarless AllanBlock on an aggregate leveling pad creates a flexible but stableretaining wall. Settlement errors that are acceptable while main-taining structural integrity include large total wall settlement andmoderate differential settlement as depicted in Figure 14.

Settlement occurs when the weight of the retaining wall structureexceeds the bearing capacity of the soil. Cohesionless soils con-sisting of sands and gravels often exhibit very little settlementwith most of the settlement occurring during or shortly after wallconstruction. Cohesive soils with high moisture content have thepotential for large time-depended settlement because the weightof the wall can actually compress the foundation soil. The settle-ment can be estimated using conventional one-dimensional con-solidation calculations. When anticipated settlement is greaterthan the construction tolerances, special design and constructionsteps need to be taken.

Post Construction Finish and Appearance

Depending on wall heights, surcharges, soil conditions and founda-tion materials, some stress cracks may occur in the wall during andafter construction. Since Allan Block walls are flexible structures,some cracking of block is likely, as are spaces between blocks as thewall moves. These openings should not exceed 0.25 in. (6 mm) anddo not affect the structural integrity of the wall.

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allanblock.com

Specification Guidelines: Geogrid Reinforcement

Every building we live and work in calls on various materials toblend strength and functionality to create a finished product thatprovides us with a safe living space incorporating the amenitiesthat we desire. The development of geosynthetics to reinforce soilmasses has paved the way to a new industry utilizing concreteblock as a facing for these composite retaining wall structures.

Allan Block walls that cannot rely on the weight of the blockalone to retain soil typically use geogrid reinforcement to devel-op a larger mass. Geogrids are flexible synthetic meshes pro-duced from high strength polyester fibers encapsulated in pro-tective coating. They work perfectly with on-site soils and mod-ular retaining wall products because of their strength, durability,workability and overall economy.

Soil reinforcement is a concept that dates back to the times ofBabylonia and the construction of the Great Wall of China whennon-degradable tree branches were placed in between layers ofcompacted soil. Whether it is tree branches or coated syntheticfibers, these products are used to create a reinforced coherentmass behind the retaining wall by stabilizing the mass andincreasing the internal strength of the soil.

Geogrid interacts with soil by using friction as well as passive resist-ance. This interaction happens both in the infill soil and the "rock-lock" connection of the block to the geogrid. The block to geogridconnection is created when the gravel material in the hollow cores

Geogrid Reinforcement Specifications

of the Allan Block units are compacted, interlocking the gravelwith the apertures of the geogrid. The gravel helps createssuperior resistance to pullout because it is a uniform, multi-point connection. With over 200 million square feet of AllanBlock products in the ground we have not had one case of theretaining wall block pulling away from the soil mass.

Most geogrid mats are stronger in one direction of orientation.The primary strength direction is commonly referred to as themachine or roll direction. Geogrid mats are typically rolledperpendicular to the face of the wall to utilize the long termallowable design strength (LTADS) of the geogrid. The trans-verse strands are in place to maintain consistent spacing ofthe load carrying strands, and can be half the strength of theprimary strands. The LTADS value of geogrid accounts forvarying soil strengths, installation damage, chemical degrada-tion, and creep.

The mechanical properties of various brands of geogrid aregiven in Table 3. LTADS values are given by the geogrid man-u f a c t u r e r st e s t i n gresults. AllanBlock con-n e c t i o nstrengths areper ASTMD6638 (alsoexplained inN C M ASRWU-1).

GEOGRIDTYPE SAND-

SILT-CLAY

LONG TERM ALLOWABLE DESIGNSTRENGTH, LTADS lb/ft (kN/m)

SAND-GRAVEL GRAVEL

REDUCTIONFACTOR

CREEP, RFcr

Fortrac 20/9-20Fortrac 35/20-20Fortrac 55/30-20

Fortrac 80/30-20

Miragrid 2XT

Miragrid 3XTMirafi 5XTMirafi 7XTMirafi 8XT

Mirafi 10XT

Strata 150Strata 200Strata 350Strata 500Raugrid 2/3-30Raugrid 3/3-20Raugrid 4/2-15Raugrid 6/3-15

Tu = 726 lb/ft + Ntan(3°)Tu = 1313 lb/ft + Ntan(8°)Tu1 = 1373 lb/ft + Ntan(41°)(Tu2 = 2600 lb/ft)Tu1 = 680 lb/ft + Ntan(57°)(Tu2= 2143 lb/ft + Ntan(14°))Tu1 = 125.6 lb/ft + Ntan(58.48°)(Tu2= 1623.5 lb/ft)Tu1 = 1420 lb/ft + Ntan(11°)Tu = 1191.1 lb/ft + Ntan(18°)Tu = 1065.4 lb/ft + Ntan(25.62°)Tu1 = 1063 lb/ft + Ntan(40°)(Tu2= 2872 lb/ft)Tu1 = 513 lb/ft + Ntan(52°)(Tu2= 1426lb/ft + Ntan(23°))Tu = 930 lb/ft + Ntan(24°)Tu = 951 lb/ft + Ntan(24°)Tu = 929 lb/ft + Ntan(25°)Tu = 848 lb/ft + Ntan(30°)Tu = 340 lb/ft + Ntan(24°)Tu = 505 lb/ft + Ntan(25°)Tu = 830 lb/ft + Ntan(29°)Tu = 1709 lb/ft + Ntan(11°)

Tu = 10.59 kN/m + Ntan(3°)Tu = 19.16 kN/m + Ntan(8°)Tu1 = 20.03 kN/m + Ntan(41°)(Tu2= 37.93kN/m)Tu1 = 9.92 kN/m + Ntan(57°)(Tu2= 31.27kN/m + Ntan(14°))Tu1 = 1.8 kN/m + Ntan(58.48°)(Tu2=23.65kN/m)Tu1 = 20.7 kN/m + Ntan(11°)Tu = 17.35 kN/m + Ntan(18°)Tu = 15.52 kN/m + Ntan(25.62°)Tu1 = 15.51 kN/m + Ntan(40°)(Tu2= 41.90 kN/m)Tu1 = 7.48 kN/m + Ntan(52°)(Tu2= 20.81kN/m + Ntan(23°))Tu = 13.5 kN/m + Ntan(24°)Tu = 13.9 kN/m + Ntan(24°)Tu = 13.5kN/m+Ntan(25°)Tu = 12.4 kN/m + Ntan(30°)Tu = 4.96 kN/m + Ntan(24°)Tu = 7.37 kN/m + Ntan(25°)Tu = 12.11 kN/m + Ntan(29°)Tu = 24.93 kN/m + Ntan(11°)

21

728 (10.60)1300 (19.00)1882 (27.50)

2815 (41.10)

839 (12.20)

1423 (20.80)2040 (29.80)2704 (39.40)3007 (43.87)

4006 (58.45)

962 (14.10)1540 (22.50)2156 (31.50)2669 (39.00)712 (10.39)1131 (16.50)1464 (21.36)2004 (29.24)

762 (11.10)1322 (19.30)1936 (28.30)

2815 (41.10)

949 (13.80)

1558 (22.70)2234 (32.60)2961 (43.20)3089 (45.07)

4116 (60.05)

1008 (14.70)1613 (23.60)2259 (33.00)2796 (40.80)737 (10.75)1172 (17.10)1517 (22.13)2077 (30.30)

572 (8.40)1243 (18.10)1783 (26.00)

2615 (38.20)

727 (10.60)

1309 (19.10)1875(27.40)2487 (36.30)2719 (39.87)

3622 (52.84)

882 (12.90)1412 (20.60)1976 (28.90)2447 (35.70)693 (10.11)1102 (16.08)1427 (20.82)1953 (28.49)

1.6271.5721.655

1.655

1.670

1.6701.6701.6701.670

1.670

1.6101.6101.6101.6101.5201.5201.5201.520

PEAK CONNECTION STRENGTH EQUATIONS, TuSEGMENT #1 lb/ft SEGMENT #1 kN/m

(SEGMENT 2) (SEGMENT 2)

Table 3: Geogrid Engineering Properties

The information in this chart has been taken from published literature and is believed to be accurate.Consult the Allan Block Engineering Department for details at 800-899-5309.

allanblock.com22

Retaining Wall products available from Allan Block

AB Stones 12° 1 sq ft. approx. 75 lbs 8 in. H x 12 in. D x 18 in. L

11 blk per m2 34 kg 200mm H x 300mm D x 460mm L

AB Rocks 6° 1 sq ft. approx. 75 lbs 8 in. H x 12 in. D x 18 in. L


AB Three 3° 1 sq ft. approx. 75 lbs 8 in. H x 12 in. D x 18 in. L


AB Classic 6° 1 sq ft. approx. 75 lbs 8 in. H x 12 in. D x 18 in. L


AB Jumbo Jr 6° 0.5 sq ft. approx. 35 lbs 8 in. H x 9.5 in. D x 9 in. L


AB Lite Stone 6° 0.5 sq ft. approx. 35 lbs 4 in. H x 12 in. D x 18 in. L


AB Junior Lite 6° 0.25 sq ft. approx. 18 lbs 4 in. H x 12 in. D x 9 in. L

44 blk per m2 8 kg 100mm H x 300mm D x 230mm

Name Setback Coverage Weight Approximate Dimensions

AB Dover 6° 1 sq ft. approx. 80 lbs 8 in. H x 10.5 in. D x 18 in. L


AB Palermo 6° 0.5 sq ft. approx. 35 lbs 8 in. H x 9.5 in. D x 9 in. L


AB Barcelona 6° 0.5 sq ft. approx. 40 lbs 4 in. H x 10.5 in. D x 18 in. L

22 blk per m2 18 kg 100mm H x 265mm D x 460mm

AB Bordeaux 6° 0.25sq ft. approx. 20 lbs 4 in. H x 10.5 in. D x 9 in. L44 blk per m2 9 kg 100mm H x 265mm D x 230mm L

Style & Performance

Actual dimensions, weights and setbacks will vary by manufacturer. Check with your local Allan Block manufacturer forexact specifications and color availability. Caps and corner blocks are also available for each of the collections.

Best Single BlockChoice

AB

CO

LLEC

TIO

N

®

Old World Antique Name Setback Coverage Weight Approximate Dimensions

AB

EU

RO

PAC

OLL

ECTI

ON

®

© 2009, 2007, 2005, 2002, 2000 Allan Block Corporation, 5300 Industrial Blvd., #100, Edina, MN Phone 952-835-5309 Fax 952-835-0013, US Pat. #5,484,236,#6,792,731, #6,322,742 & #6,854,236 Canadian Pat. #2,012,286 & #2,133,675 Australian Pat. #682,394 & #133,306 Europe Pat. #649,714 & #99,308,421.9Germany Pat. #69,423,563.6 Japan Pat. #3,142,107 Mexico Pat. #189,846 Taiwan Pat. #NI-72269 Int’l And Other Patents Pending DOC. #R0901-0309

This technical specification manual will allow a wall designer tosource and reference specific information for use in developingproject documents. The information contained in this manual

is for use with Allan Block products only.

Allan Block Retaining Walls - Spec Book

Documents

Transcript of Allan Block Retaining Walls - Spec Book