What is the most effective technique for Ground improvement in terms of Shear Strength and Compressibility for an Uncontrolled fill of Cohesive Soil (Fill Depth 5-10 m )?
Preloading (surcharge) or preloading with vertical drain system is the most effective method to reduce the settlement ..also the other methods like stone columns or lime columns are also followed to improve the characteristics of soft clay up to a deeper depth. ok all the best in your research..
Deep mixing method (DMM), Prefabricated Verticle Drain (PVD) + Prefabricated Horizontal Drain (PHD) with or without Surcharge loading, Stone Column and Sand Pile.
If the soil contains a higher amount of moisture, organic matter, pH and also required a higher shear strength (> 500 kPa) then DMM is the most effective method.
DMM is expensive but most effective for mitigating settlement, liquefaction, slope instability and also achieving high shear strength within a short period (within a month).
The selection of an appropriate method depends on the purpose and what you are trying to achieve. I would ask these questions (and perhaps more) before making a selection: What will be the function of this soft soil? what are the available methods of ground improvement at the location of your project? what are the geotechnical characteristics of the soft soil that you have? how is the ground profile and specifically drainage characteristics of the strata that neighbour the soft ground?
The problems associated with soft soil are generally poor drainage, high water content, low shear strength and high compressibility. Such soils can also possess high sensitivity to disturbance. You might be surprised to see a drop in the shear strength whilst you try to apply improvement techniques sometimes due to that reason. Installation of PVDs can facilitate drainage and accelerate consolidation when used with preloading. Electro-osmosis is an alternative to that. These methods differentiate themselves from the others as they technically cause less disturbance to the ground.
Muhammad Usman Arshid For fill depth up to 10 m and soft Cohesive Soil you can try the HVDM method. You can check my presentation to know the benefits of the HVDM method for soft ground improvement.Presentation Overview of High Vacuum Densification Method (HVDM) for soft...
I think the best method for improvement soft clay is using reinforcement column for example use a stone columns or deep soil mixing column or if the soil is so week you can use Geosynthetic-encased column.