SOIL IMPROVEMENT

SOIL IMPROVEMENT

Soil Improvement

Drilling & Grouting
Grouting in general terms is known as the injection of a fluid which sets or gels into a crack or voids. The scope of grouting covers a wide range from simple filling operation to complex engineering application, which can be used either for reduction of permeability or strengthening of foundations. Commonly used grout materials are cement and water, including certain chemicals, which can be used as additives.
Access to the cracks or voids is usually provided by holes drilled at fixed spacings by destructive drilling technique such as top-hammer or down-the hole hammer systems using an air compressor.
The injection of grout has to be limited or adjusted by suitable pumps.

Jet Grouting
Jet Grouting is a general term for a variety of techniques employing one, two or three fluids to mix in situ or replace soil underground with cement based grout mix. The common denomination of those methods is the use of very high pressure in the injected fluid, which mixes or displaces the soil, rather then permeating it as in conventional grouting techniques.
The possibility of creating treated horizons or columns of improved soil results in a variety of applications ranging from vertical cut-offs to bottom plugs, from underpinning to underground strutting elements.

Vibro Compaction/Stone Columns
Vibro compaction is a technique used to densify granular soils which are typically clean sands (fines content generally less than 10%) using special vibrators.
The vibratory energy is used to rearrange the particles of the sand in a denser state. The vibrations are produced by a rotating eccentric probe driven into the soil down to the required depth.
Cohesive and mixed layered soils generally do not densify easily when subjected to vibration alone. Hence, the Vibro-Replacement, Stone Columns has been specifically developed as improved technique of the Vibro process, widening the range of soil types that can be improved with the deep vibratory method.
With Vibro-Replacement, dense columns of crushed material (coarse gravel) are formed into the soil in order to increase bearing capacity, reduce settlement, improve shear resistance and, in seismic areas, mitigate the potential for liquefaction.
The stone columns and the in-situ soil form together an integrated system having lower compressibility and high shear strength.

Deep Soil Mixing
Soil Mixing is a method of soil improvement by which materials of various types, but usually of cementitious nature, are introduced and blended into the soil through hollow, rotated shafts equipped with cutting tools, and mixing paddles or augers, that extend for various distances above the tip. The ‘binder’ materials may be injected in either slurry or dry form. The treated mass that results generally has a higher strength, lower compressibility, and lower permeability than the virgin soil.

Dynamic Compaction
Dynamic Compaction (DC) is a Ground Modification technique whereby loose soils can be effectively and economically densified to improve its mechanical characteristics and allow construction of structures directly on compacted soil, without the need of deep foundations or soil replacement.
The method involves dropping heavy steel pounders repeatedly on the ground at regularly spaced intervals. The weight and height of pounding depend on the degree of compaction desired. The usual range of pounder weight is between 12 Ton to 25 Ton and the drop height can be up to 25m.
DC method is applicable for a wide variety of soil conditions including saturated/unsaturated loose Sands, even with the presence of silty pockets, dune sands, inorganic fill, reclaimed soils with variable characteristics and sizes even with the presence of large-sized boulders, landfill deposits and collapsible soils.
DC has been extensively used to compact loose soils to depths of up to 10m, in order to increase the bearing capacity, decrease post-construction settlement and mitigate liquefaction risk in case of seismic events.

Key features:
- Applicable for wide range of soils with fines content up to 35%, down to significant depths up to 10m
- Very fast production (more than 50,000 sq.m/crane/shift/month)
- Well adapted to large scale projects
- Increases the bearing capacity of soils, reduces the post-construction settlements and eliminates the risk of soil liquefaction in case of seismic events
- With a global treatment, DC can be undertaken ahead of the foundation design
- Very sustainable technique: no disposal, no aggregate, no cement…

DC technique is well suited for a wide range of applications and projects with different sizes up to several million sq.m, covering Industrial buildings, oil & gas facilities, Infrastructure constructions, platforms and logistics facilities, commercial and residential buildings, tanks, artificial islands, road and railway embankments, land reclamations. DC technique was implemented as value engineering alternative to deep foundation or soil replacement for a large number of structures throughout the world.

Dynamic Replacement
Dynamic Replacement (DR) is an extension of Dynamic Compaction (DC) to compressible soils (such as soft clays, silt, sabkha...) where large diameter columns (up to 2.5 m diameter) of very dense granular materials are constructed by dropping heavy pounders from great heights onto the soft soil.
DR technique can be implemented as a global treatment for the complete site or localized treatment under foundations only in order to increase the soil bearing capacity and reduce the total and differential post-construction settlements.
This method combines the advantages from both Dynamic Compaction and Stone Columns techniques by creating large sized granular columns with high stiffness and internal shear resistance and overall improvement of mechanical characteristics of the intermediate soil.
A large variety of readily available granular materials may be used for the construction of the DR columns. Clean well-graded sands may be the most suitable; however, other sources such as dune sands, gravel/sand mix, concrete rubble/crushed gravel mixed with sand etc. may also be successfully used.

Key features:
- Applicable for wide range of soils down to significant depths up to 8m
- Very fast production (more than 30,000 sq.m/crane/shift/month)
- Well adapted to large scale projects
- Very flexible specifications for the backfilling material
- DR method is suited for very soft soils such as Sabkha & soft clay
- Speed-up the consolidation of soft clays due to potential drainage through the DR columns

Thanks to its efficiency, versatility and high-cost saving, DR method is well suited for wide range of applications and projects with different sizes up to several million sq.m, covering Industrial buildings, oil and gas facilities, Infrastructure constructions, platforms and logistics facilities, commercial and residential buildings, tanks.

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