Influencing factors for unloading characteristics in saturated clay

When a gravity structure, such as a caisson or a jackup spudcan, is pulled out from the saturated soft clay foundation, a negative excess pore pressure will be developed, which greatly increases the uplift force. Meanwhile, field tests show that the extraction rate has a great influence on uplift resistance. The stress path, the stress-strain characteristics and the development of pore pressure of Tianjin saturated soft clay under unloading condition are studied based on the triaxial extension tests. The research indicates that the higher consolidation pressure and the larger strain rate produce larger negative pore pressure and larger shear strength. Tianjin soft clay is characterized by the strain softening and the shear failure strain of 5% to 10%. Finally, the results of pore pressure coefficient tests are obtained.