超固结粉质黏土快速大剪切力学特性

    MECHANICAL PROPERTIES OF OVERCONSOLIDATED SILTY CLAY UNDER FAST SHEAR CONDITIONS

    • 摘要: 本文借助于先进的多功能大型高速高压环剪试验机,通过进行不同应力历史、剪切速度和正应力等条件下的系列试验,对吉林长春地区广泛分布的超固结粉质黏土在快速大剪切位移条件下的力学响应特性进行了试验研究。试验结果显示,前期固结历史和剪切速度不仅对超固结粉质黏土的抗剪强度变化具有显著的影响作用,并且对于其峰后应变软化亦产生明显的影响。在相同剪切速率和正应力条件下,前期固结压力越大,其峰值强度和残余强度值越大。不同剪切速度下的试验结果表明,在具有相同应力历史的条件下,峰值强度和峰后应力降低随着剪切速度的增大而增大。剪切速度越快越有利于土应变软化的产生以及剪切面的形成。在快速大剪切条件下对长春地区超固结粉质黏土抗剪强度变化起主要作用的是剪切过程中土体结构的变化和剪切面的生成,而剪切过程中孔隙水的作用并不显著。

       

      Abstract: This paper employs a sophisticated ring shear apparatus and conducts a series of fast rate ring shear tests to quantify the mechanical properties of Changchun silty clay. The tests are carried out under overconsolidated and fast ring shear conditions. The test results are obtained under different preconsolidation pressures, shear rates and normal stresses. The effects of stress history and shear rate on the shear resistance of the over-consolidated silty clay are examined and discussed. It is found that the preconsolidation pressures and shear rates exert remarkable influences on the peak shear strengths and the following post-peak reductions in strength. The shear strengths became greater when the preconsolidation pressures were higher. The test results at different shear rates show that if the OCR values are the same, both the peak strength and the post-peak strength reduction become greater as shear rate increases. The soils with high shear rate are prone to have the strain softening. The faster shear rate tests are more favorable to development of slip surface that lead to the ultimate stable shear strengths. The variations of shear resistance under fast shear rate in ring shear tests are mainly due to the structural changes in the shear zone, while the influence of pore water during fast shearing is negligible.

       

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