Brochure 67-03 E

The Soilcrete® –

Jet GroutingProcess

Contents

3 History

4 Soilcrete® –Jet Grouting Process

6 Process Variations

7 Construction Forms

8 Construction Sequences

10 Stabilisation

11 Sealing

12 Addresses

3

Small scale underpinning works were thebeginnings of an unusual way of jet grouting.To reach todays state of the art, additionaldevelopment was necessary.

• The process was modified to suit differ-ent types of soils.

• The application was developed step bystep to provide solutions to a variety ofproblems.

• Equipment was developed and improved.

• A general licence for Soilcrete wasissued by the Institute of ConstructionTechnic in 1986.

This brochure reports on the state of theSoilcrete technique today.

With the aquisition of a licence in1979 for the Jet Grouting processand the introduction into Germanyunder the trademark “Soilcrete”,Keller Grundbau GmbH enteredinto a new field of soil stabilisation.

Soilcrete – History

Computer design andoptimisation of compli-cated Soilcrete elementsby Keller‘s own softwareSoiljet®

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100

80

60

40

20

00,60,002 0,006 0,02 0,06 6,0 20 600,2 2,0

Soilcrete – Jet Grouting Process

The jet grouting process

The jet grouting process “Soilcrete” is recog-nised as a cement soil stabilisation. With theaid of high pressure cutting jets of water orcement suspension having a nozzle exitvelocity ≥100 m/sec eventually air- shroudedthe soil around the borehole is eroded.

The eroded soil is rearranged and mixedwith the cement suspension. The soil-cement mix is partly flushed out to the topof the borehole through the annular spacebetween the jet grouting rods and the bore-hole. Different geometrical configurations ofSoilcrete elements can be produced. Theerosion distance of the jet varies accordingto the soil type to be treated, the kind ofSoilcrete process and the jetting fluid beingused, and may reach up to 2.5 meter.

Applications

In contrast with the conventional groundstabilisation methods Soilcrete may be usedfor stabilisation and sealing of all kind of soilranging from loose sediments to clay.This applies also for non homogeneous soilformations and changing soil layers, includingorganic material. Soft rock formations havealso been treated by Keller Grundbau GmbH– for example sandstone with weak graintexture.

The name “Soilcrete” derives fromthe concept “soil” to “concrete” aform of soil with a concrete consist-ence, a description that characterisesthe type of soil stabilisation.

Application limits for grouting techniques

Clay Silt Sand Gravel

Pass

ing

by w

eigh

t [%

]

Grain size [mmØ]

Synthetic SolutionsSodium Silicate

[lv]SolutionsSilicate Gel [hv]

Ultra fine Cement

Cement Suspension

Mortar

lv = low viscoushv = high viscous

economicaluneconomical

Soilcrete - Jet Grouting®

Coubles

5

50

0

100%

602,00,060,002 7 28

25

14 42210

50

75

100

The Soilcrete – properties

Soilcrete acts in the ground according to thespecification either as a stabilisation or as asealing structure. A combination of bothproperties is increasingly required.

The compressive strength of Soilcreteranges from 2 to 25 N/mm2 and is deter-mined by the cement content and the re-maining portion of the soil in the Soilcretemass.

The sealing effect of Soilcrete against wateringress is achieved by selecting a suitablegrout suspension and if necessary by theaddition of Bentonite. The type and quantityof the injected grout material as well as thekind and volume of the remaining soil parti-cles in the Soilcrete mass guiding the sealingproperties.

Depending on the nature of soils, Soilcretecut-offs are able to reduce the coefficient ofpermeability by several decimal powers.High quality requirements in respect of thedegree of sealing effect necessitate extensiveproduction efforts. For many applicationsboth the strengthening and sealing character-istics of the Soilcrete elements are used. Theselected suspensions need to be compositedaccordingly.

Soilcrete cubaturesforming a firm con-tact with any kindof foundation forms

Soilcrete sealingmixtures testedin a laboratory

Compressive strength of Soilcrete Development of Soilcrete-strength

Type of soil silt sand gravel

Compressive ≤5 ≤10 <25strength[N/mm²]

Soilcrete pump andcontrol station

Grain size [mmØ]

Pass

ing

by [

wei

ght

%]

silt sand gravel

Setting time [days]

Compressive strength in % of the final strength

non-cohesivesoil

cohesive soil

6

Soilcrete – Process Variations

Soilcrete is produced in three differ-ent ways. The method to be used isdetermined according to the prevail-ing soil conditions, the geometricalform and the required quality of theSoilcrete elements.

Soilcrete S

(Single direct process) operates with a groutjet of min. 100 m/sec. exit velocity for simul-taneous cutting and mixing of the soil with-out an air schroud.

The Soilcrete S process is used for small tomedium sized jet grout columns.

Soilcrete D

(Double direct process) operates with agrout jet of min. 100 m/sec exit velocity forsimultaneous cutting and mixing of the soil.To increase the erosion capability and therange of the grout jet, air shrouding bymeans of shaped air jet nozzle is used.

The D process is mainly used for panel walls,underpinning and sealing slabs.

Soilcrete T

(Triple separation process) erodes thesoil with an air shrouded water jet of min.100 m/sec exit velocity. Grout is injectedsimultaneously through an additional nozzlelocated below the water jet nozzle. Thegrout pump pressure ranges above 15 bar.A variation of this process operates withoutair shrouding of the water jet.

The T process is used for underpinningworks, cut off walls and sealing slabs.

The triple Soilcreterods provide sepa-rate flows of air,water and grout tothe jet nozzle holder

Grout Backflow

Grout jet

Backflow

Air shroudedgrout jet

Air

Grout

The drilling bit islocated below thejet nozzle holder.During drilling thesuspension is re-leased through thedrilling bit.

Backflow

Air shroudedwater jet

Air

GroutWater

Grout jet

7

A

B

C

Soilcrete – Construction Forms

Interlinked bodies –constructed fromuniform elements

Sealing slabs

Panel walls

Box walls

Column walls

Deep foundation

Soilcrete – Basic forms

The Soilcrete basic forms may be arrangedand combined in any way to form each typeof element.

Exposed testfield with several Soilcrete disksfor a sealing slab

Exposed Soilcrete elements of anunderpinning wall in sandy soils

Interlinked Soilcrete elements

Panel wall with sealing slab Underpinning elements

The basic geometrical form of Soil-crete elements is created throughmovements of the drill rods:

• Pulling of the drill rods without rota-tion resulting in panels – if severaljet nozzles are used multiple panelsmay be produced.

• Pulling and swivelling create seg-ments.

• Pulling and rotating create completecolumns.

One sided

Column

ABC

---

Quarter ColumnHalf ColumnComplete Column

Lamella

Twin sided

8

Soilcrete – Construction Sequences

Soilcrete site installations consist of storage containers, silos and a compactmixing and pumping unit. Several high pressure hose connections and controlcable lines connect the pumping unit with the Soilcrete drilling rig at the instal-lation point. The mast length of the rig varies from 2.00 m in cellars or shaftsand up to 35 m in open areas.The borepoints are normally located in small trenches equipped with sludgepumps. From there the excess material, water-cement-soil mixture is pumpedto setting ponds or tanks.

1 Drilling

Drill rods equipped with jetnozzle holder and drill bit areused to drill the jet groutinghole down to the requireddepth. Normally the jet groutmixture is used as drill flush-ing to stabilize the boreholeduring the drilling operation.In masonry and concrete, spe-cial drilling bits are used.

2 Jetting

The disolution of the graintexture with a powerful fluidjet starts at the lower end ofthe Soilcrete element. The ex-cess water soil cement mix-ture is removed to the surfacethrough the annular spacebetween drill rod and bore-hole wall. The pre - selectedproduction parameters areconstantly monitored.

3 Grouting

For all Soilcrete variations ce-ment suspension is injectedunder pressure simultaneouslywith the erosion of the soil.The turbulences caused by thejetting technique results in theuniform mixing of the groutwith the soil within the treat-ment zone.

Until the grout in the Soilcreteelements starts setting hydro-static pressure in the boreholeis kept by backfilling grout intothe hole from time to time.

Small drilling rigsmanufactured byKeller provide ac-cess to confinedworking places

To backflowrecycling

Air WaterCement/Bentonite

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5000

6000

7000

8000

00 250 5000 250 5000 100 20020 0 200 5 10 0 50 100

Process Monitoring

Up to 12 different parameters for the con-struction of Soilcrete elements may be re-corded and used by the engineer-in-chargeof supervision and control.

Core recovery fromSoilcrete elements

Important construct-ion parameters maybe electronically re-corded

4 Extension

Soilcrete elements of each formmay be constructed fresh onfresh as well as fresh againstfirm and combined and con-nected in a variety of ways.

The working sequence followsthe technical requirements andthe conditions of the structureto be treated.

Backflow recyclingMixer/pump

Operation paneland basic stationof recording unittype M4

Optical and manual checking as well ascontrols and tests according to the require-ments laid down in the license issued by theInstitute of Construction Technik ensurequality workmanship.

Time

[sec]

Process: Soilcrete-D-Process (1.0.0)Inventar: 130481 Site: 6814225Lot: 0 Point: 19 Ref. No.: 3Date: 12.06.95 Time: 16:287:30 Interval: 2 sekWeight:Legend:

Total time: 149.63 min Max. Depth: 6.3 m Length column: 6.1 m

Flow

[l/min]

Groutpressure

[bar]

Drillingpressure

[bar]

Depth

[m ]

Revo-lutions

[rpm]

Progress

[m/min]

10

Foundation modification Shaft supports

Deep foundation Earthpressure relief

Tunnel protectionUnderpinning

Foundation restoration Soilcrete -Horizontal

Soilcrete tunnel protection ismainly constructed in loose soilsbelow or close to endangeredstructures, sometimes with theaim of reducing the groundwateringress into the tunnel excavation.

Underpinning by means of low de-formation gravity walls sometimesalso used as a ground water sea-page barrier, may be safely con-structed even from confinedworking areas.

Horizontal Soilcrete columns pro-tect tunnel drives in loose soil for-mations. They are constructedfrom working faces and are hori-zontal or slightly inclined.

Changes in utilisations or modifica-tions of buildings often require anenlargement or alteration of thefoundation. Soilcrete is an economi-cal and flexible solution for thistask.

Soilcrete is used for new founda-tions which require special care inview of nearby existing structuressuch as historical buildings orcomputer centres.

Structures exposed to earth pres-sures, such as historical walls, abut-ments, avalanche galleries, steepslopes protections or quay wallsmay be relieved by the addition ofor connection to a statically calcu-lated backup Soilcrete body.

Soilcrete for Stabilisation

Underpinning work for adjacent construction pits is one of the main tasks of soilstabilisation – followed by foundation modifications and restoration.

Soilcrete opens new ways for tunnel constructions in loose soils.

Soilcrete – Applications

Historical buildings may be endan-gered in the event of settlementsoccurring. Soilcrete provides a safefoundation with the maximumstructural protection.

Shafts with intersecting Soilcretecolumns are constructed if a vibra-tion free installation is requiredand/or the shafts enter into groundwater bearing strata.

11

Dam sealing Joint sealing

Sealing slabs Groundwater exits

Column walls Sealing cover

Vault slabsPanel wallsSoilcrete panel walls to cut offground water are used belowroads and buildings, for crossingpipelines and to subdivide buildingpits into different excavation sec-tions. According to the sealing re-quirements single or multiple pan-els may be constructed.

For small building pits and shaftswith reduced width Soilcrete slabsare used as prevention against thewater uplift pressure, reducing therequired depth of slabs normallyrequired to resist the hydrostaticuplift.

In the event of higher mechanicalstrain by shearforce, danger of un-dermining or of a high imperme-ability requirements, cut off wallsof intersecting Soilcrete columnsmay be constructed.

The Soilcrete cover protects thegroundwater below buildingsagainst affects from constructionactivities and old toxic waste de-posits.

Soilcrete may be used to repairdam cores or enlarge cut-off wallsin or below dams.

For sealing of joints between piles,sheet piles or other constructionparts in the ground the Soilcretewing- jet is applied.

Soilcrete sealing slabs are con-structed by means of overlappingcolumns within an uplift proofdepth. The sealing slabs may beconnected to any kind of verticalsealing systems.

Sealing walls are often used astemporary ground water barriers.The reinstatement of the perme-ability may be reached using theSoilcrete process to wash out thebinder material from predeter-mined sections.

Soilcrete for Sealing

Building pit walls constructed of deformation and ground water resistant Soilcreteunderpinning elements, combined with low permeable Soilcrete slabs enables theexecution of deep building pits without the need for large scaleground water lowering.

Environmental safe mineral binder materials are used for Soilcrete.

A company of Keller Group plc

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