基于结构性及各向异性的软黏土变形性状试验

摘要

针对结构性和各向异性两大要素对天然软黏土变形性状的影响，对上海天然沉积软黏土进行一维固结试验、K 0固结试验以及三轴不排水剪切试验。结果表明：上海天然沉积软黏土具有明显的结构性及各向异性特征；压缩特性在结构屈服破坏前后存在显著差别，具有结构性软黏土所特有的分段特征；不同初始固结应力下的等压及偏压固结不排水应力路径曲线最终都趋近于同一临界状态；在初始有效固结应力低于软黏土的结构屈服应力时，应力应变曲线呈应变软化型，随着初始有效固结应力的增加，当其超过结构屈服应力后，应力应变曲线逐渐呈现硬化型特征；在初始有效固结应力相同且低于结构屈服应力的前提下，偏压固结模式所对应的不排水剪切峰值强度高于等压固结模式，且屈服后的应变软化程度相较于等压固结模式更高；在不排水剪切强度达到峰值后，等压和偏压固结模式下的应力应变曲线逐渐趋于重合；在初始有效固结应力相等的情况下，等压固结模式下产生的孔隙水压力较偏压模式下要高。%In order to find the influence of structure and anisotropy on deformation character of natural soft clay,one-dimensional consolidation test,K 0 consolidation test and triaxial undrained shear test were carried out for soft clay from natural sedimentation in Shanghai.The results show that the properties of soft clay from natural sedimentation in Shanghai are characterized by structure and anisotropy;the compression properties are significantly different before and after structural yielding,and the compression curve is divided into two parts as structural soft soil;the undrained stress path curves with different initial consolidation stresses finally approach the same critical state under isotropic and anisotropic consolidation modes; when initial effective consolidation stress is lower than structural yielding stress of soft clay,the stress-strain curve is strain softening,and when the initial stress is higher than the yielding stress,the characteristic of stress-strain curve is gradually hardening with the increase of the initial stress;when the initial stresses are the same,and are lower than the yielding stress,the peak of undrained shear strength under anisotropic consolidation mode is higher than that under isotropic consolidation mode,and the strain softening after yielding is higher than that under isotropic consolidation mode;after the peak of undrained shear strength arrives,the stress-stain curves under isotropic and anisotropic consolidation modes approach coincidence;when the initial stresses are the same, the pore water pressure under isotropic consolidation mode is higher than that under anisotropic consolidation mode.