基于大三轴试验的土石混合体强度特性与影响因素

为更为详细地探讨山区土石混合体的力学特性,综合考虑含石量、含水量与岩石完整性等因素的影响,采用正交试验方法对土石混合体填料的大型三轴剪切试验进行设计,并运用邓肯-张模型对得到的三轴试验参数进行反演研究。结果表明:土石混合体中影响内摩擦角的因素从大到小分别为含石量、含水量、岩石完整性;试件在各围压下剪切时,开始阶段偏应力与轴向应变近似成比例关系;当轴向应变超过2%时,偏应力增长速率减小,呈现出明显的应力-应变非线性;当混合体达到最大偏应力之后,仍可以保持在增加轴向应变的同时,偏应力不减小,表明土石混合体材料的软化特性不明显;含石量对试样体应变的影响较含水量与岩石完整性更显著,在含石量较低时体现为剪缩性,含石量较高时更多体现为剪胀性;邓肯-张模型的拟合结果与大三轴试验数据的相似度较好,表明邓肯-张模型能模拟土石混合体在不同围压下的应力-应变关系。

Study on Strength Characteristics and Influencing Factors of Soil-rock Mixture Based on Large Triaxial Test

In order to analysis the mechanical properties of soil-rock mixture in mountainous(SRM) area in more detail, the influences of stone content, water content and rock integrity are comprehensively considered. The large-scale triaxial shear test of soil-rock mixture filler was designed by orthogonal test method, and the parameters of which were inverted by Duncan-Zhang model.The results show that factors that affect the internal friction angle from large to small are stone content, water content and rock integrity in SRM. When samples of SRM are sheared under various confining pressures, the deviating stress is approximately proportional to axial strain at beginning stage. When axial strain of samples exceeds two percent, deviating stress stress growth rate decreases,which shows obvious nonlinear of stress-strain.When the maximum deviatoric stress is reached, the samples can keep axial strain increases while the deviatoric stress does not decrease, which indicates that the softening characteristics of soil-rock mixtures are not obvious.Stone content affect the volume strain of samples is more significant than both water content and rock integrity.When the stone content is low, the samples of SRM show shear shrinkage. When the stone content is high, the samples of SRM show shear shrinkage while when the stone content is high, the samples of SRM show dilatancy.The fitting results of Duncan-Chang model are similar to large triaxial test datas.The good similarity indicates that Duncan-Chang model can simulate the stress-strain relationship of SRM under different confining pressures.