静动荷载作用下海洋软黏土刚度弱化特性研究

Stiffness degradation of marine soft clay under monotonic and cyclic loadings

利用动三轴联合弯曲元测试系统对嘉兴原状海洋软黏土进行了一系列不排水条件下单调和循环三轴试验,分析静动荷载作用对正常固结软黏土的小应变剪切模量及刚度弱化特性的影响。试验结果表明,土体小应变剪切模量在单调荷载作用下先减小后增大,在循环荷载作用时则逐渐减小并最终保持稳定。在中到大应变下,饱和软土归一化动模量随循环单幅应变发展不断减小,且其值相较于单调剪切时的割线模量略大。研究发现,土体动模量弱化规律与动荷载作用下的小应变刚度特性密切相关,在不同固结围压和循环加载条件下表现出很好的一致性。研究结果可为该区域海洋构筑物设计提供依据,也可供其他同类型工程借鉴。

A series of undrained monotonic and cyclic triaxial tests are conducted on Jiaxing intact marine soft clay by using a testing system combined with triaxial apparatus and bender element to investigate the small strain shear modulus and stiffness degradation of isotropically consolidated soft clay.The results indicate that the small strain shear modulus decreases and then increases under monotonic loading,but it tends to decrease continuously under cyclic loading.At medium to large strains,the normalized equivalent modulus of saturated soft clay decreases gradually with the development of single-amplitude cyclic strain with a larger degradation rate than the monotonic secant modulus.In addition,a fairly unique relationship exists between the cyclic degraded stiffness and small strain shear modulus,which is barely affected by the initial confining pressure and cyclic stress condition.The findings obtained in this study can provide the basis for the design of offshore structures in this area,and can also be used as a reference in other engineering projects.