循环荷载作用下饱和砂砾土的破坏机理与动强度

不同研究者对砂砾土动强度影响因素的认识存在相互冲突之处。针对含砾量、相对密度、初始有效固结应力和固结比4个主要因素,对10组不同含砾量的饱和砂砾土开展了系列循环三轴试验,提出了砂砾土破坏评价准则;引入二元聚集模型,研究了饱和砂砾土的不排水动力特性及其动强度的量化方法。研究结果表明:不同试验条件下砂砾土存在两类破坏机理,即均等固结条件下表现为达到零有效应力状态的循环液化,非均等固结条件下表现为过大累积轴向变形的循环失效;引入砂砾土骨架结构孔隙比概念,砂砾土动强度CRR随砂砾土骨架结构孔隙比的增大而降低,且其降低趋势呈良好的指数函数关系。

Undrained cyclic failure mechanisms and resistance of saturated sand-gravel mixtures

There are conflicting versions of influences of different factors on cyclic resistance of sand-gravel mixtures. Considering four main factors, gravel content, effective lateral confining stress, relative density and consolidation stress ratio, a series of cyclic triaxial tests were performed on the sand-gravel mixtures with 10 groups of gravel contents. The test results and findings are summarized as follows: (1) There are two failure mechanisms of the sand-gravel mixtures under different test conditions, i.e., cyclic liquefaction and cyclic failure; (2) The excess pore pressure of a 100% and the accumulated axial strain of a 5% are adopted as the criterion for the cyclic liquefaction and the cyclic failure of the specimens, respectively; (3) An index of the sand-gravel skeleton void ratio () is employed to represent the packing condition of skeleton particles and filler particles in the sand-gravel mixtures; (4) The mean correlation representing the exponential relationship between the cyclic resistance ratio (CRR) causing cyclic liquefaction or cyclic failure at the presupposed number of cycles and the of sand-gravel mixtures is derived.