Compaction Grouting

Contents

General Description

Applications of Compactation Grouting

Working procedure

Quality Control

Preliminary research, Geotechnical considerations and

collection of on-site data

Improvement conditions. Previous experience

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General Description

The method of Static Grouting is based on the injecting of a low mobility mortar into the soil so that

the injected mixture does not flow through the soil and remains concentrated around the injection

point. This mortar is injected at a pressure of up to 40 bar and with a settlement on the Abrams

cone of less than 8 cm, allowing for correct densification. The injected material fills the gaps and

compacts or stabilises the soil surrounding the area treated.

The mortar cement then sets to give it resistance and hardness.

The soil must be displaced during injection without breaking its structure.

1. Installation of the grouting piping

The boring is drilled using rotary or

rotary-percussion equipment

depending on the characteristics of

the soil.

2. Compactation Grouting

The mortar is prepared in the mixer

and injected by pressure into the soil

using a specific pump for this type of

work.

Meanwhile, the grouting piping is

gradually inserted or withdrawn,

creating a column made up of

almost round bulbs that join

together.

3.Compactation by phases

To e n s u r e u n i f o r m s o i l

compactation, grouting is worked

onto a primary and then a

secondary mesh. In the case of

localised treatment, the grouting is

worked at the points and with the

gradients defined by the calculation.

Low mobility

mortar

Boring

equipment

Parameter

register

Pump and

mixer

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3

Soil improvement

Foundation stabilising and underpinning

Cavity filling

Improvement of soil with low supporting capacity,

increasing its relative density. Compacting of non-

cohesive soils, especially those with low or medium

density with alternating hard or cemented layers. It can

be used as an alternative or in addition to pile foundations

or soil improvements using gravel columns.

Increasing or restoring the supporting capacity of the soil

underneath existing foundations, e.g. in the event of an

increase in excess load or to repair damage produced by

settlements. This technical is an alternative to the Jet

Grouting procedure and/or can be used as a preliminary

treatment to apply Jet Grouting and Fracturation

Grouting. Recovery of or increase in the supporting

capacity along the shaft or the point of existing deep

foundations.

In very porous, eroded soils or those with cavities, e.g. in

landfill areas that have not been sufficiently compacted,

areas affected by karstification, soil damaged by the

breakage of water pipes, etc.

Applications of Compactation Grouting. Types

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4

The Static Compactation method is especially suitable for the treatment of non-cohesive soils,

particularly those with low to medium densities.

This technical is also used in cohesive soils in order to insert elements of greater resistances and

supporting capacity, thus improving the behaviour of the soil regarding excess loads.

The use of this technique on saturated clays causes a momentary increase in interstitial pressure

and, therefore, can be combined with other techniques.

Advantages:

- Possibility of use in specific treatments.

- High output leading to fast installation.

- Wide range of possible applications.

- Possibility of use in a wide variety of soils.

- Application capacity in sites with difficult access and with heavy gauge restrictions.

- Due to previously imposed grouting criteria, no excess mortar consumption is produced.

- The mortar columns do not have to be connected to the footing or the structure.

- Non-destructive treatment compatible with existing foundations.

- Cheap alternative compared with the scaling and replacement of soil or piling.

- Capacity to reach depths out of the range of application of other methods.

- Applications to localised areas with confined strata.

Applications of Compactation Grouting. Scope of application

Clay

Size of particles [mmø]

Soilcrete /Jet Grouting®

Soilfrac /Fracturation grouting®

Compactation grouting

Silicate solutions

Micro-cement

Cement suspension

Silt Sand Gravel Pebbles

Range of applications for grouting techniques

Techniques

Sie

ve

passin

g[w

eig

ht

%]

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5

Working procedure

Decide on the details of the site with the client's and/or the owner's experts.

Choice and installation of the movement control points for the structure to be reinforced. The

first reading will be made prior to the boring and grouting work.

Boring is drilled to the required depth, as previously defined during the design stage.

Once the required depth is reached, the mortar is injected, controlling the pressure and the

volume injected into the soil. Once the volume defined in the project for each stage or that

compatible with all grouting criteria has been injected, the rod is withdrawn between 30 and

50 cm to start the next grouting stage.

On certain occasions, boring may be required in reverse direction, i.e. from top to bottom.

The mortar used is made up of sand, cement and plastifying additives.

This entire process consists of the following stages:

Grouting criteria:

The displacement of the soil surrounding the point at which grouting is applied causes earth

movements. The criteria to complete the grouting stage and go onto the next stage are listed

below:

When the injected volume of mortar defined for each stage is reached.

When the maximum pressure indicated in the project specifications is reached.

When mortar circulates through the boring drill.

When the structure or the work platform moves outside the acceptable range established by the

calculations.

Installation of the grouting piping

Boring.

Positioning is important.

Recording of information on the soil obtained from

boring.

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-

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Start of grouting

Normally from bottom to top, although the opposite is

also possible.

Mortar control and quality is important.

The pressure and/or volume is normally limited.

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-

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Continuing grouting

Control the pressure, volume and mortar cone.

The planning of the sequence of treatment points is

extremely important.

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1.

2.

3.

4.

The quality and suitability of the fresh mortar must be controlled by measuring the settlement on

the Abrams cone. Simple compressive strength will also be checked.

The level of Compactation reached may be controlled using the following parameters,

depending on the objective sought and on the conditions of the soil:

- Assessment of the data collected by the parameter recording system installed in the boring

and grouting equipment.

- Control of movements on the work platform or the structure to ensure the correct working

parameters.

Depending on the type of soil and the improvements sought, the control tests will be defined

and may include:

- Penetrometric tests (CPT, SPT) before and after the grouting process on non-cohesive,

crosshole or other soils.

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4 Quality Control

The depth, the pressure and the volume of the mortar are continuously

recorded. The consistency of the mortar and the movements of the existing

work platform and structures are continuously controlled.

Penetrometric tests (CPT, SPT)

before and after compactation

grouting in non-cohesive soils.

Movement control using remote laser level located at a set point.

10,0

0

1,50

Ø BORE HOLE 114 mm

8,0

0

30º

1,00

RIVER AND EMBANKMENT SECTION - GROUTING PROPOSAL

15,76

1,50

2,0

0

1,50

10,0

0

1,00

30º2,0

0

Dep

th(m

)

Before treatment

After treatment

Inje

cte

dsectio

n

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5 Preliminary research, Geotechnical considerations and collection

of on-site data

Preliminary research

Geotechnical considerations

Data collection

Good knowledge of the conditions of the subsoil is necessary for effective compactation grouting

treatment. A full geotechnical report and knowledge of nearby structural conditions will make the

design of a correct grouting campaign easier.

There is a series of requirements that must be met for correct compactation grouting:

- There must be sufficient vertical stress on the layer to be treated to allow for the grouting to

displace the soil horizontally. Excessive surface elevation will prevent correct densification.

- In saturated soils, the grouting speed must be slow enough to allow for the interstitial pressure to

be dissipated. The grouting sequence is very important.

- Soils containing saturated or expansive clay must be avoided.

- Greater displacement will be produced in more compressible layers. Compactation grouting

focuses improvements on more needy areas.

Skilled KELLERTERRA staff responsible for the work will systematically record the following data:

- Elevation and settlements in the soil and on foundations around the boring.

- Volume injected during each stage.

- Grouting pressure reached during each stage.

- Completion criteria reached during each stage.

- Daily work record.

6 Improvement conditions. Previous experience

A 7 t/m pressure of enclosure is normally required to maximise densification. Limited

densification will be produced with lower pressures. Pressure may be caused by the weight of

the soil, excess load or foundation loads.

When the aim of the treatment is to densify the soil, pressure and replacement rate criteria will be

applied to each grouting stage. This rate or ratio is determined according to the initial soil density

and to the displacement required to achieve an effective improvement.

Experience has shown that the space between treatment points must not exceed 2 or 3m.

The criterion for maximum grouting pressure prevents the soil from breaking and lifting and limits

the volume of mortar grouting.

The vertical grouting stages are normally separated by intervals of between 30 and 100 cm.

Replacement rate= 5=15% (Normal values)Injection volume

Volume of soil treated�

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Miguel Yuste, 45 Bis

E28037 Madrid

Tel.: 914 237 561

Fax: 914 237 501

Web: www.kellerterra.com

Mail general: kellerterra@kellerterra.com

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