温度和含冰量对冻结土石混合体力学特性的影响

冻结土石混合体是一种力学特性极为复杂的岩土材料，其力学特性对温度和含冰量等因素非常敏感。然而到目前为止，对于其力学行为随温度、含冰量及法向压力等的变化特征仍然缺乏足够的了解。本文开展了一系列的冻结土石混合体的直剪试验，研究了温度、含冰量及法向压力对冻结土石混合体剪切特性的影响。结果显示温度、含冰量及法向压力对冻结土石混合体的剪切行为都有重要影响。在其他条件相同时，冻结土石混合体的抗剪强度随着温度的下降呈指数形式增长。当温度高于-5℃时，抗剪强度增加很快，而当温度低于-5℃时，抗剪强度仅有微小增加。在-5℃时，冻结土石混合体的抗剪强度随着含冰量的增加先增加后减少。抗剪强度最大值出现在含冰量在11%左右。冻结土石混合体的粘聚力随着含冰量的增加先迅速增加，在含冰量大于11%以后，粘聚力又有微小下降，而内摩擦角随着含冰量的增加缓慢减小。冻结土石混合体的抗剪强度随着法向应力的增加而增加，但在高法向应力下，其塑性增强。

INFLUENCE OF TEMPERATURE AND ICE CONTENT ON MECHANICAL PROPERTIES OF FROZEN ROCK-SOIL MIXTURE

Frozen rock-soil mixture is a special geotechnical material. Its mechanical behavior varies with temperature and ice content is still poorly understood. Direct shear tests were conducted to investigate the influence of temperature, ice content and normal stress on shear strength of rock-soil mixture. Results indicate that temperature, ice content and normal stress all have significant influence on shear strength of rock-soil mixture. For constant ice content and normal stress, shear strength of rock-soil mixture rises rapidly with temperature when the temperature is higher than-5℃.When temperature drops below -5℃,most free water is frozen and only small amount bond water is left,shear strength only has a slight increase with temperature. The shear strength of rock-soil mixture increases sharply when ice content is low. The shear strength reaches a peak value when the ice content is about 11% by weight. After that point, the shear strength has a slight decrease. Detailed research reveals that the cohesion of rock-soil material increases with ice content until the ice content reaches 11%, and then it tends to level off. But the internal friction angle decreases monotonously with ice content.The shear strength of frozen rock-soil mixture increases with the normal stress increasing. The plasticity of frozen rock-soil mixture increases under high normal stress.