低围压与不同温度作用下土石坝护坡土石混合体力学特性

Study on mechanical properties of earth-rock mixture for earth-rock dam slope protection under low confining pressure and different temperatures

针对寒区土石坝护坡存在的隆起、错位、坍塌等冻胀破坏问题,以寒区某土石坝护坡工程砂砾料垫层、坝体填土土石混合体为研究对象,开展了低围压下不同温度和含石量的土石坝护坡土石混合体三轴试验,研究了不同围压、温度、含石量对土石混合体力学特性的影响。结果表明:在较低围压作用下,含石量较低试样的应力-应变关系曲线为应变软化型,随着围压增大,试样的应力-应变关系曲线变为应变硬化型;在常温条件下,当围压较低时,不同含石量的试样呈现先剪缩后剪胀的现象,当围压较高时,试样则一直表现为剪缩,且围压越大,剪缩量越大;在不同冻结温度下,土石混合体的体积应变呈现先剪缩后剪胀的变化规律,且试验温度越低,剪胀变形越明显;随着含石量的增加,砾石之间的嵌合作用增强,土石混合体逐渐成为砾石骨架结构,土石混合体的内摩擦角增大而黏聚力减小;温度的降低使得土石混合体试样内部的水逐渐相变成冰,在结冰胶结作用下,土石混合体的内摩擦角和黏聚力都有所增加。

In view of the frost-heaving damage problems such as uplift,dislocation,and collapse that are common in earth-rock dam slope protection in cold areas,using the gravel cushion and dam fill earth-rock mixture of an earth-rock dam slope protection project in cold areas as the research objects,this study conducted triaxial tests on the soil-rock mixture of earth-rock dam slope protection with different temperature and rock content under low confining pressure,and analyzed effects of different confining pressure,temperature and rock content on the mechanical properties of the soil-rock mixture.The results show that the stress-strain curves of the samples with low stone content are strain softening type under lower confining pressure,and gradually change to strain hardening type with the increase of confining pressure.Under normal temperature conditions,when the confining pressure is low,the volume deformation of the sample with different stone content shows the phenomenon of contraction followed by the dilatancy,but when the confining pressure is high,the volume deformation of the sample shows the phenomenon of contraction,and the greater the confining pressure,the greater contraction.At different freezing temperatures,the volume deformation of soil-rock mixture shows the phenomenon of contraction followed by the dilatancy,and the lower the test temperature,the greater the dilatancy deformation.With the increase of rock content,the chimerism between gravels is strengthened,and the internal friction angle of the soil-rock mixture increases but the cohesion decreases.With the decrease in temperature,the water inside soil-rock mixtures gradually turns into ice.Under the action of ice cementation,the internal friction angle and cohesion of soil-rock mixtures increase.