海积软黏土的强度特性与桩土界面剪切速率效应

Effects of shear rate on strength properties and pile-soil interface of marine soft clay

针对中等结构性的海积软黏土,开展了剪切速率影响下原状土的三轴CU试验与软黏土–钢管桩环剪试验,分析了其抗剪强度与桩土界面特性的演化规律,并对桩周土剪切后再固结的界面性状进行了模拟试验。结果表明,该土样的抗剪强度与内摩擦角均随剪切速率的增大而单调增大,而黏聚力则相反;发现在不排水条件下,桩土接触界面的峰值强度与摩擦角随着剪切速率的增大也随之增大,应变软化现象更加明显,但相应的残余强度与摩擦角变化甚微;桩周软黏土历经剪切大变形重新固结后,桩土界面的强度性状呈现出峰值强度降低与残余强度增大的特征。

The CU triaxial tests and ring shear tests on interface between steel pipe pile and soil of a kind of intact marine soft clay with medium structure are carried out under influence of shear strain rate, and the variations of strength properties and pile-soil interface properties of the tested soil with shear strain rate are analyzed. Moreover, simulation tests on the reconsolidated soft clay around the pile after shearing are also conducted to analyze the strength behaviors of pile-soil interface. The results show that the shear strength and internal friction angle of the tested soil increase with the increasing shear strain rate monotonously, while the variation characteristics of the cohesion are opposite. Under the undrained condition, it is also found that the peak shear strength and internal friction angle of the pile-soil interface increase with the increasing shear strain rate, and the strain softening phenomenon becomes more obvious, however, the corresponding variations of residual shear strength and internal friction angle are very small. Although the peak shear strength of reconsolidated soil around the pile after large shear deformation tends to decrease, the residual shear strength increases, which shows the strength recovery characteristics of pile-soil interface.