滨海软黏土蠕变特性的三轴试验

Triaxial Test on Creep Properties of in Coastal Soft Clay

为探讨天津滨海典型软黏土的蠕变特性,利用英国GDS动三轴试验系统,开展了考虑围压、加荷比以及排水条件等因素下的三轴蠕变试验研究,得到了不同条件下滨海软黏土的应力-应变-时间关系曲线.试验结果表明:天津滨海软黏土具有非线性蠕变特性,其蠕变变形演化特征受结构性制约,低围压条件下,蠕变等时曲线近似为线性,无明显的屈服特性;当围压较大时,蠕变等时曲线呈现折线特性;排水条件下的蠕变等时关系曲线比不排水条件下的非线性程度明显,排水条件下其体变性状总体上表现为剪缩,蠕变变形速率和变形量均低于不排水条件;不排水条件下软黏土的初始蠕变变形速率和变形量与围压和加荷比有关,相同偏应力水平下,固结压力越大,初始蠕变速率越大,达到稳定蠕变阶段的时间越短,蠕变变形量越小;初始固结压力一致时,加荷比越大瞬时蠕变速率越大,破坏应力值越小.

Triaxial creep tests considering different confining pressures, loading ratios and drainage conditions are done by the British GDS dynamic triaxial tester, the stress-strain-time curves of coastal soft clay under different condi- tions are obtained, and the creep properties of typical Tianjin coastal soft clay are explored. The research indicates that typical Tianjin coastal soft clay has the nonlinear creep properties, and that the creep deformation properties are re- stricted by structural characteristics. Under low confining pressure, the creep curves are approximately linear with no significant yield characteristics, while the creep curves have the broken line features under high confining pressure. The creep curves under drained condition have a more obvious degree of nonlinearity than those under undrained con- dition, the volume properties under drained condition are of shear reduction, and both creep deformation and rate are lower than those under undrained condition. The initial creep deformation rate and deformation of soft clay under undrained condition are related to confining pressure and loading ratio, and under the same deviatoric stress level, the bigger the consolidation pressure and the higher the creep rate are, the shorter the time to reach steady creep stage and the smaller the soil deformation will be. Under the same initial consolidation pressure, a higher loading ratio leads to a bigger instantaneous creep rate and a smaller destruction pressure.