Pressure Grouting

> Providing additional soil-strengthening benefits

Page Contents

Background of TechniqueApplicationsFoundation & Soil DensificationControlled LiftingMitigation of Tunnel SettlementsMaterials & EquipmentSummary

Background of TechniqueCompaction Grouting is a specialized technique for in-situ densification of compactable soft or loose soils. A stiffgrout is extruded into a soil mass to form an expanding bulb. Maintaining a controllable bulb of grout is the essencesof this technique, as illustrated in Figure 1 .

Any soil capable of being mechanically compacted can be densified by compaction grouting. The extent and theintensity of soil densification depends on the injection point configurations, the depth of the injections, the grout mix,and the amount of grout injected. Compaction grouting is effective in most man-made fill, organic soil, sand, silt, peat,and most clays. The improvement of soil strength can be demonstrated by the Cone Penetration Testing Methodbefore and after compaction, as shown in Figure 2 .

Figure 1

ApplicationsCompaction grouting is versatile: it lifts, levels, stabilizes, supports, fills and densifies soil for new construction andexisting structures, and it also reduces machinery vibration. The Pressure Grout Company has completed hundreds ofsuccessful projects involving compaction grouting for:

> Building Sites--Site improvement for structural support and prevention of soil liquefaction> Building & Structures--Settlement mitigation, foundation stabilization, controlled lifting> Machinery Pads--Controlled lifting and leveling, stabilization, vibration reduction> Tunnelling--Surface settlement prevention, heading stabilization> Drilled Piers--Lifting to grade without excavation, restoration of deformed pipes> Pipelines--Lifting to grade without excavation, restoration of deformed pipes> Tiebacks--Anchor development

The Pressure Grout Company http://www.pressuregrout.com/services.htm

3 of 17 12/9/2008 1:38 AM

The Pressure Grout Company 9/12/2008

page 1/15

http://www.pressuregrout.com/services.htm

Figure 2

Hundreds of jobs have established that compaction grouting is an effective and economic method of compacting soils.

Foundation SoilDensification & Strengthening

Compaction grouting can provide an answer to the problem of differential settlement of structures. The versatility ofthe technique makes it the method of first choice for soil densification in areas where access to the site with heavyequipment is difficult or where noise is a problem. Grout injection points can be angled to reach areas under afoundation that otherwise could not be reached, as shown in Figure 3.

Figure 3

Controlled LiftingCompaction grouting can be used effectively for the controlled lifting of foundations, slabs, and other structures.Lifting takes place when the pressure at the bulb exceeds the weight of overburden, structures, and the shear strengthof the soil cone above it. At that point, the soil shears, and the grout pressure lifts the soil and the structure built upon


4 of 17 12/9/2008 1:38 AM


page 2/15


it, as shown in Figure 4.

Figure 4

By the careful use of this technique, entire structures can be lifted and leveled to precise specifications. Unlike otherlifting or supporting techniques, compaction grouting supports structures and appurtenances on sound soilfoundations.

Mitigation of Tunnel SettlementsTunelling generally produces ground movements, which are manifested in the form of surface settlements or theloosening of adjacent soil and rock. Compaction grouting can be used for the prevention of surface settlement, forheading stabilization, and for remedial work in adjacent soil.

Prevention of Soil LiquefactionCompaction grouting can be effective in reducing or eliminating the liquefaction potential in earthquake-prone areas.For unimproved sites or for existing structures, the technique can be successfully employed to avoid soil liquefaction.For deep liquefiable soil layers, for inaccessible sites, or for sites where noise can not be tolerated, compactiongrouting is the primary choice for achieving soil densification without vibration or impact.

Materials & EquipmentCompaction grouting is accomplished by using a lean, thick grout mix of portland cement and silty sand. Natural sandswith a range of 25 to 30% silts usually are used. The water content of the grout is adjusted to maintain a slump (ASTMC-143) of 1 to 1.5 in., with a maximum of 2 in.

The Pressure Grout Company has designed and built much of the equipment it uses on compaction groutingassignments. This equipment, capable of achieving grouting pressures of up to 2000 psi, can be operated at distancesseveral hundred feet from the injection site. The operation of Pressure Grout Company at a job site is shown in Figure5 .


5 of 17 12/9/2008 1:38 AM


page 3/15


Figure 5

The Pressure Grout CompanyThe Pressure Grout Company has extensive experience in all types of pressure grouting for site development, newconstruction, and the stabilization of existing structures, ranging from giant dams and highrise buildings to individualhomes and buildings of all types. We work closely with owners, engineering firms, contractors, and public agenciesthrough the United States. We:

> Build, operate and maintain our own equipment> Have one of the few research and development laboratories for grout materials and mixes> Have a staff that includes engineers with extensive knowledge and experience in soils engineering> Are licensed contractors and members of the Associated General Contractors and> Have broad, in-depth grouting experience that extends over a period of more than 45 years.

TOP

Chemical Grouting is the injection of near-water-viscosity liquids into a cohesionless soil to create an impervioussandstone-like mass...

Used For:

> Solidifying sandy soils> Controlled erosion of sand cliffs> Stabilizing slopes and excavations> Stabilizing foundations and tunnel headings> Reducing the liquefaction potential of sandy soils> Controlling or shutting off groundwater seepage> Sealing interlocks of sheet piling

Page Contents

Background of TechniqueApplicationsUnderpinning FoundationsAnchoring TiebacksSupporting ExcavationsControlling GroundwaterOther ApplicationsEquipmentSummary

Background of TechniqueChemical Grouting is the injection of one or more near water-viscosity liquids into a cohesionless soil to create and


6 of 17 12/9/2008 1:38 AM


page 2/15


impervious sandstone-like mass, as shown in Figure 1 . Because chemical grouting literally creates "instant sandstone"as tough as that of mother nature, it is one of the most successful techniques available today for stabilizing soils andcontrolling groundwater. The applications of chemical grouting are almost endless, and new uses are documentedalmost daily.

In many cases, chemical grouting offers substantial advantages over other techniques for stabilizing soils or controllinggroundwater: economy, simplicity, flexibility, risk reduction, less noise, and minimal accessiblity requirements.

The successful use of the technique requires knowledge and skill to analyze the soil and determine the optimumchemical system, pressure, gel time, and other variables. For more than 45 years, The Pressure Grout Company hasprovided chemical grouting services. We have designed our own specialized mixing and grouting equipment,conducted research on numerous chemical combinations, and developed more than 15 different chemical systems fora wide range of applications.

ApplicationsChemical grouting is used for stabilizing foundations, underpinning structures, plugging tunnel leaks, creatingimpervious grout curtains, and other applications where the control or shutoff of groundwater or the solidification ofsand or fissured rock is required--above or below the water table--in fresh-water or saltwater environments.

The Pressure Grout Company has succefully used chemical grouting for applications, such as

Solidification of sandy soils and fissured rock for

> Underpinning foundations> Providing support for excavations> Stabilizing tunnel headings> Preventing surface settlement> Stabilizing slopes> Controlling erosion> Reducing liquefaction potential> Creating sandstone anchors for tiebacks and tiedowns

Groundwater shutoff for

> Structures> Excavations> Fissured rock> Tunnels and tunnel linings> Pipelines and sheet piling> Dams and landfills


7 of 17 12/9/2008 1:38 AM


page 5/15


Figure 1

Underpinning Foundations


8 of 17 12/9/2008 1:38 AM


page 6/15


For existing foundations, chemical grouting can be used to increase the load-bearing capacity of an underlying soil,prevent settlement, or reduce the potential for soil liquefaction during a seismic event. The injected chemical groutcombines with the soil to form a "sandstone" footing or a pier capable of transferring loads to lower strata, as shown inFigure 2 . Such injections can form columnar piers, 3 to 5 feet in diameter, thereby underpinning existing foundations.

Anchoring TiebacksChemical grouting is used to form "sandstone" masses that provide the necessary anchorage requirements for tiebacksor tiedowns in cohesionless solis. The technique is also highly effective in producing large bulkheads that provide theload-carrying capacity for tiebacks.

Supporting ExcavationsThere are at least three general ways in which chemical grouting can be used to support excavations: by providing agravity wall of solidified soil, by solidifying soil in conjunction with another method of lateral support, and throughminimal grouting to prevent sand sloughing and/or water seepage through the lagging, as shown in Figure 2 . Ifconditions permit, the sides of an excavation can be cut back to a suitable slope, and a grout blanket produced on thesurface of the slope to prevent erosion and surface sloughing.

Controlling GroundwaterChemical grouting has been successfully used to shutoff the seepage of groundwater into tunnels, basements,excavations, and pipelines. Permanent or temporary shutoffs can be accomblished by using different chemicalsystems. The Pressure Grout Company has been involved in hundreds of water shutoff jobs, involving a widespectrum of applications and conditions.

Other ApplicationsThere are numerous other applications of chemical grouting, including a reduction in the liquefaction potential ofsandy soils, sealing interlocks of sheet piling, controlling erosion of sand cliffs, and seepage.

EquipmentThe Pressure Grout Company has designed and built specialized mixing, pumping, and injection equipment forchemical grouting. This equipment can be operated at distances several hundred feet from the injection site. The workof The Pressure Grout Company on a chemical grouting assignment is shown in Figure 3.

Figure 2


9 of 17 12/9/2008 1:38 AM


page 7/15


Figure 3

The Pressure Grout CompanyThe Pressure Grout Company can provide solutions to your soil and groundwater problems. If your project requires aunique application, our staff can help find a suitable grouting method and develop effective field applications. Ourideas, experience, and chemical systems can make the difference.

We have extensive experience in all types of chemical grouting for site development, new construction, and thestabilization of existing structures. We work closely with owners, engineering firms, contractors, and public agenciesthroughout the United States. We


TOP

Lense Grouting is cement grout injection to hydraulically fracture the soil and produce horizontal grout lenses, whichserve as water barriers and provide in-situ reinforcing of soils.

Used For:

> Reducing moisture-related shrinking/swelling of clay soils> Reinforcing soils on slopes> Reinforcing soils adjacent to retaining walls and large diameter pipes> Increasing friction and end bearing for piles and piers> Reducing vibrations of heavy machinery> Stabilizing loose backfill in trenches

Page Contents

Background of TechniqueApplicationsReduction of Expansive Clay MovementsSoil ReinforcementOther ApplicationsEquipmentSummaryBackground of Technique

Lense Grouting is a specialized technique the injection of a cement grout to hydraulically fracture the soil and produce


10 of 17 12/9/2008 1:38 AM


page 8/15


multiple, water-resisting, horizontal grout layers that (1) reduce the moisture-related shrinking/swelling of clay soilsand (2) provide in-situ reinforcing of soils.

In theory and in practice, at a given pressure, a grout with the proper viscosity (consistency) will fracutre a soil massin a plane normal to the pricipal stress (vertical) or along bedding planes. Based on this theory and utilizing its manyyears of grouting know-how. The Pressure Grout Company experimented with the technique and developed practicalapplications for lense grouting.

Figure 1

In its applications, lense grouting uses a cement base grout with the consistency of thick cream. This grout is injectedinto the soil mass, fracturing it horizontally and creating multiple lenses. Each lense is designed to be about 10 feet indiameter and 1/8 of an inch thick. The formation of these lenses has been demonstrated by the excavation of actualinjections in the field.

For expansive clay soils, injections are generally made at regular intervals to a depth below the seasonalwetting/drying zone. The result is the creation of multiple water barriers, as shown in Figure 1 .

ApplicationsThe Pressure Grout Company has developed applications and used lense grouting with success in such cases as:

> Structures--Grouting the perimeter to reduce and eliminate soil expansion and contraction> Creep--To reduce and eliminate creep by reinforceing loose formations and expansive soils> Soil Strengthening--To strengthen loose soils, particularly in close proximity to retaining walls> Piles and Piers--To increase friction and end bearing> Trenches--To stabilize loose backfill

Experimental uses of lense grouting, based on studies carried out at Stanford University, include the in-situreinforcement of soil to allow steep excavation slopes, earth mat foundations, and other applications.

Reduction of Expansive Clay MovementsExpansive clays are known for their shrinking and swelling with changes in moisture content. Seasonal and differentialchanges in the moisture content of these clays can cause heaving and settlement, as well as differential movements ofstructures built upon them. These effects can be reduced or eliminated by lense grouting, which introduces moisturebarriers within the clay mass.

Soil ReinforcementSoil reinforcement can be achieved by providing overlapping lenses of cement grout. The level of reinforcement canbe increased by shortening the lensing interval, increasing the grout strength, and having greater overlapping of lenses.


11 of 17 12/9/2008 1:38 AM


page 9/15


Overlapping lense grouting has been successful in strengthening loosened soils, improperly compacted fills, soilsloosened by over-excavation, etc., as shown in Figure 2 .

Figure 2

Other ApplicationsThe applications for lense grouting are numerous. The Pressure Grout Company has used the technique to

> Develop skin friction for sinking piles in soft clays, as shown in Figure 3.> Support uncompacted soils in deep trenches.> Strengthen soils loosened by over-excavation, e.g. for elevator shafts or pits,> Provide water barriers for foundations in soils with subsidence characteristics, and> Form reinforced earth mats in collapsible soils under existing structures.

Figure 3

EquipmentThe Pressure Grout Company has designed and built specialized mixing, pumping, and injection equipment for lensegrouting. This equipment can be operated at distances several hundred feet from the injection site. The work of The


12 of 17 12/9/2008 1:38 AM


page 3/15


Pressure Grout Company on a lense grout assignment is shown in Figure 4 .

The Pressure Grout CompanyThe Pressure Grout Company has extensive experience in all types of lense grouting for site development, newconstruction, and the stabilization of existing structures. We work closely with owners, engineering firms, contractors,and public agencies through the United States. We

> Build, operate and maintain our own equipment,> Have one of the few research and development laboratories for grout materials and mixes,> Have one of the few research and development laboratories for grout materials and mixes> Are licensed contractors and members of the Associated General Contractors, and> Have broad, in-depth grouting experience that extends over a period of more than 45 years.

Figure 4

TOP

PressGrout Piles™ are steel piles with large diameter grout footings.

Used For:

> Increasing load-bearing capacity> Transferring loads to competent lower strata> Eliminating or reducing settlements> Mitigating soil liquefaction> Increasing pull-out resistance> Improving shaft friction and for> Angled (raked) piles with high lateral resistance> Pile groups with high concentrated loads

Page ContentsBackground of TechniqueApplicationsRaked PilesPile GroupsMaterials & EquipmentSummary

Background of Technique


13 of 17 12/9/2008 1:38 AM


page 11/15


PressGrout Piles™ are steel piles with a grout footing (bulb) at the bottom of the pile to increase load-bearingcapacity, as illustrated in Figure 1.

Either driving or drilling may be used for the installation of grouted piles, depending on soil conditions, siteaccessibility, and load-carrying requirements.

The installation of these piles does not require large machinery or equipment at the site itself, since routing equipmentcan be parked at a suitable location near the site.

Figure 1

The Basic PilesFor grouted pile installations, a steel pipe is first installed in position; then a predetermined amount of grout is injectedto create a footing at the bottom of the pile. This grout footing has two main purposes: To compact the soils aroundthe tip of the pile, and to act as a footing for the pile. Generally, a grouted pile consists of a small diameter pipe(nominal 2 to 4 inches) with a single bulb at the bottom, although other pile diameters and grout configurations arepossible.

ApplicationsPressGrout Piles™ are superior to comparable size piles for a number of reasons: First, they have a footing at thebottom of the pile for higher load bearing capacity. Second, they can be angled for higher lateral resistance. Third,they can be installed with minimal access or headroom. And fourth, they can be installed where there is a hard layerof soil, which overlays softer deposits.

> PressGrout Piles™ are useful and cost effective in applications for new construction or existing structures, such as> Residential or commercial structures on improperly filled ground> Structures requiring improved seismic or wind resistance> Structures with low concentrated loads or loads distributed over large areas underlain by very soft soils> Structures where it is necessary to eliminate machinery vibrations> Structures requiring a high pull-out resistance to reduce overturning moments, for example tie downs or tie backs,as shown in Figure 2> Slabs supporting heavy machinery on poor bearing strata> Inaccessible sites where the use of heavy equipment is not possible> Sites where there are restrictions on vibration or noise> Sites where it is necessary to transfer loads vertically or laterally to more favorable lower strata


14 of 17 12/9/2008 1:38 AM


page 12/15


Figure 2

Raked PilesPressGrout Piles™ can be installed at any angle to maximize load-carrying components. These piles have a particularadvantage for structures that require a high component of lateral resistance because of seismic, wind, or hydrostaticsoil/water loading, as shown in figures 1 and 3.


15 of 17 12/9/2008 1:38 AM


page 13/15


Figure 3

Pile GroupsPile groups or clusters are used for high concentrated loads. Some of the piles can be vertical, while others can beangled. Figure 3 illustrates a typical configuration of a pile group.

Piles With Increased Shaft FrictionAlthough PressGrout Piles™ are largely bearing piles, shaft friction contributes to the pile capacity. In the absence ofa competent-bearing layer, the shaft (skin) friction plays a major role in pile carrying capacity; hence, an increase inteh friction force can be important.

Unlike conventional piles, friction capacity can be greatly improved by using multiple grout bulbs along the shaft, asillustrated in Figure 3.

Materials & EquipmentGalvanized steel pipe is usually used for PressGrout Piles™, but in sites where corrosion is not a problem, black steelcan be substituted for galvanized steel. A sand-cement mixture with water is used for the grout to produce a lowslump, less than 2 inches (ASTM C-143). This grout is injected under pressure to displace the soil and form a bulbaround the tip of the pipe.

The Pressure Grout CompanyThe Pressure Grout Company can provide solutions to your soil and groundwater problems. If your project requires aunique application, our staff can help find a suitable grouting method and develop effective field applications. Ourideas in geotechnical stabilization can make the difference.

We have extensive experience in all types of geotechnical grouting for site development, new contruction, and thestabilization of existing structures. We work closely with owners, engineering firms, contractors, and public agenciesthrough the United States. We


TOP


16 of 17 12/9/2008 1:38 AM


page 14/15


Pressure Grouting

Documents

Transcript of Pressure Grouting