421 ABSTRACT: Soft ground is widely distributed especially along the coastal area, having large potential for settlement with low inherent shear strength. In the recent years, improvement of soft soils has been extensively implemented for the various development projects all over the world due to extremely limited stable construction sites. Although there are a variety of ground improvement techniques under different categories, ground improvement by using column-type techniques are used on an increasing scale for soft ground improvement. Sand compaction pile (SCP) method represents the most known column-type technique for improving the engineering characteristics of soft soils. SCP is a method of constructing large diameter sand column in the ground. The main function of SCP application is to accelerate soil consolidation by shortening the drainage path and activating radial drainage, thereby increasing the undrained shear strength of the soil while reducing its post- construction settlement. This method of ground improvement has been widely used for rapid improvement of soft ground and in near-shore regions for land reclamation works. In India, the granular columns have been used to improve ground for container freight station at Navi Mumbai and the construction of dry dock at Pipavav shipyard. In this study, the consolidation and shear strength behavior of soft clay installed with SCP in 100mm diameter and 200mm long clay specimens is modeled using consolidated undrained triaxial tests under different confining pressures ranging from 50kPa to 575kPa. The composite specimens were prepared with area replacement-ratio (a s ) of 6.25, 10.24, 16, 20.25 and 64% in different specimens by driving a PVC casing into the sample and then backfilling the cavity with sand column after removing the casing in a custom-designed setup. The SCPs were then compacted by using a pneumatic compactor. The test results show that the consolidation and stress-strain behavior of the clay was highly influenced by the presence of SCP. The insertion of SCPs into soft clay has shown to have a positive effect on the load carrying capacity of the clay, resulting in a composite soil mass that has greater shear strength and improved stiffness compared to the unreinforced clay due to increased reinforcement area ratio. In addition, SCP also acts as vertical drain in the clay thus accelerating the dissipation of excess pore water pressures that are generated during loading. Thus, sand compaction piles currently stand as one of the most viable and practical techniques for improving the mechanical properties of soft clays. 1 INTRODUCTION Soft clay deposits with high water content exhibit low bearing capacity and high compressibility characteristics. Due to increasing demands for more and more industrial and residential areas and Compressibility and strength behavior of soft clays reinforced with sand compaction piles B.A. Mir Department of Civil Engineering, National Institute of Technology Srinagar-190 006, J&K, Kashmir, India; E-mail: p7mir@nitsri.net; bamiriitb@gmail.com; bashiriisc@yahoo.com; Cell: +91-9419002500 A.Juneja Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai -400076, India International Conference on Geotechnical Engineering. 2013