Enhancement of Bearing Capacity of Soft Soil Using Geosynthetics

Abstract

The vast areas of Bangladesh are composed of very soft to soft fine-grained soil with high compressibility. Thus, the ground undergoes excessive settlement due to the construction of any structure over the ground. As such conventional foundation systems could not be chosen in this kind of soil due to its low bearing capacity. In such a case, ground improvement or reinforcing the ground is necessary. Thus, research has been carried out to find out an appropriate ground improvement technique with the application of ground reinforcement and study its effectiveness against the reduction of ground deformation and improvement of bearing capacity. Here, numerical analysis has been carried out with the finite element method, using the elastoplastic subloading tij model.

Bearing capacities for different over consolidation ratios (OCRs) have been analyzed. Then the effect of reinforcement was compared by changing its depth below the foundation for different OCRs. Bearing capacity is also checked by replacing the soft clay with granular soil between the foundation and reinforcement. Bearing capacity has been analyzed with and without reinforcing the ground below the foundation. It is found that higher values of OCRs have a positive effect on the bearing capacity. Again, reinforcement increases the bearing capacity of the soft clay, and the increment of the bearing capacity depends on the depth of the reinforcement, OCR, and improved area of the ground underneath the foundation.

For a higher value of OCR, the bearing capacity of soft soil is increased. Once ground below the foundation is reinforced, its effect on bearing capacity varies with its location. The effect has been analyzed by placing reinforcement at D/B=0.05, D/B=0.10 and D/B=0.20, where D is the depth of reinforcement and B is the width of the foundation. There is an increasing trend of bearing capacity once the location of reinforcement has been changed from D/B=0.05 to D/B=0.10. On the contrary, the bearing capacity decreases for the placement of reinforcement at D/B=0.20. Bearing capacity is further increased by introducing a granular layer between the foundation and reinforcement.