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海相沉积软土广泛分布于我国沿海地区,是典型的结构性土,具有灵敏度高、承载能力低等特点。通过自钻式旁压试验调查软土场地的原位力学特性,获得了29.0 m深度范围软土层的原位水平应力、临塑压力、不排水抗剪强度、剪切模量等力学指标。结果表明,软土的旁压试验曲线可分为应力平衡阶段、弹性阶段、塑性阶段和破坏阶段4个阶段;破坏阶段之前软土的卸载会造成有效应力的显著降低,在工程实践中对软土卸载过程的稳定性应予以关注;软土的剪切模量具有明显的非线性特征,采用非线性分析法得到的剪切模量较为合理。通过对试验结果的拟合,建立了原位水平应力和临塑压力随深度变化的经验公式,可为工程中该两类参数的确定提供参考依据。
Marine sedimentary soft soil is widely distributed in China’s coastal areas, is a typical structural soil, with high sensitivity, low carrying capacity. Through the self-drilling pressure test, the in-situ mechanical properties of soft soil were investigated. The horizontal stress, plastic pressure, undrained shear strength and shear modulus of soft soil in the depth of 29.0 m were obtained. The results show that the test curve of the side pressure of soft soil can be divided into four stages: stress equilibrium phase, elastic phase, plastic phase and failure phase. Before the destruction phase, the unloading of soft soil can reduce the effective stress remarkably. In engineering practice, The stability of soil unloading process should be concerned; the shear modulus of soft soil has obvious nonlinear characteristics, and the shear modulus obtained by nonlinear analysis method is more reasonable. Through fitting the test results, the empirical formula of in-situ horizontal stress and plasticizing pressure with depth is established, which can provide reference for the determination of these two kinds of parameters in engineering.