Soft Soil Improvement



Dynamic compaction is the process of improving sub soil to great depth. The imparted stress to the soil from high energy of a free falling weight rearrange the soil and brings the soil to a denser packing.

By this, the bearing capacity of the ground is significantly increased with great reduction in total and differential settlement.






Dynamic Replacement is the variation of the technique of Dynamic Compaction, that of delivering impact energy to the ground by means of dropping a large mass from a significant height, that is applied in soft, saturated cohesive soils and soft organic soils. The effects of the impacts from a falling mass that generate the benefits of Dynamic Compaction are not realized in these types of ground and instead Dynamic Replacement offers a means of creating stiff, high modulus inclusions within a soil mass affording a much greater global modulus in the ground.




Vibro compaction is a deep compaction technique to Densify granular soils-in-situ by means of a vibrating poker (called vibroflot) penetrating in to the soil under the combination of high frequency vibrations and jets of water or air at the bottom of the vibroflot. Under the influence of simultaneous vibration and saturation loss granular soil particles are re-arranged in to more compact positions and lateral confining pressures within the granular soil mass are increased.






The construction of a new embankment or structure induces additional stresses on the ground that can create unacceptable long term residual settlements during the life of the structure or highway. A preloading program can be designed to induce these settlements in an accelerated timeframe and therefore minimize the long term residual settlements to within acceptable limits for the structure. Vertical Drains can be used in low permeability soils (clays, silts) and can significantly increase the rate of consolidation. Prefabricated Vertical Drains consist of a flexible plastic core (flat or cylindrical in shape) wrapped in a spun-bond filter fabric and can be installed to depths of more than 50 m. Depending on the type and nature of the soils to be treated, it is also possible to install sand or stone drains.
A temporary surcharge embankment needs to be combined with the installation of the Vertical Drains in order to expedite full or partial primary consolidation as well as induce several decades of secondary consolidation (creep) settlement.

The typical pre-consolidation program usually includes :
1) Installation of prefabricated Vertical Drains to the bottom of the 
Compressible layer. PVD are laid out and installed on a grid pattern and
to the depth required by the design (to reduce the consolidation time
and increase the apparent mass permeability of the soft soils);
2) placement of the preloading embankment in phases (due to potential risk of slope failure) and additional temporary surcharge embankment as designed. The real-time evolution of the main geotechnical parameters (settlements, pore water pressure, horizontal displacements.) is monitored through out the consolidation period. Instruments are installed to validate the design and the safe phasing of the construction of the embankment.
The monitoring of the geotechnical parameters is also used to back-analyze the main design hypothesis and results. The design parameters and calculations are optimized to fit the observed results and updated settlement and consolidation targets are used to assess the consolidation process
General functions of geotextile are drainage, filtration, separation and reinforcement.
Geotextiles are mainly used as separators and reinforcement. Reinforced geometrical – acts as filter layer for pwp dissipation & provides high tensile modulus to resist deep slip failure. ROC PEC 100 chosen as provided appropriate tensile modulus for design – it is a composite high strength geotextile basal reinforcement material. It was also used as stiffening reinforcement to embankment.  Overall the total reinforcement increases the restoring moment against failure in order to provide an adequate Factor of Safety against failure. Design called for up to 5 layers of reinforcement.

Bamboo Fascine laid over Separator Geotextile TS-80 Controlled Stage Construction of Geotextile Reinforced Embankment of 7.0 m high over a 9.0 m of extremely soft soil using high tensile strength Geotextile.


The Embankment with Berm Constructed by high tensile strength Rock PEC-100 Geotextile