等向固结饱和黏土卸载特性影响因素研究
Influencing factors for unloading characteristics in saturated clay
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摘要: 饱和黏土地基中的沉箱、自升式钻井船的桩靴等结构物或结构基础上拔时,常常遇到难以拔出的现象,同时现场试验表明上拔速率对上拔阻力有很大的影响。通过等向固结的减压三轴伸长试验,研究了固结压力和变形速率对卸荷状态下天津饱和软黏土的应力路径、应力-应变特性以及孔压发展规律的影响。试验表明,固结压力越大,负孔压峰值越大,抗剪强度越大;变形速率越大,负孔压峰值越大,抗剪强度越大。天津软黏土卸荷时呈现应变软化的特性,并且剪切破坏时应变为5%~10%。同时,给出孔压系数试验结果。Abstract: 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.