冻融风化边坡岩体破坏机理研究

FAILURE MECHANISM OF SLOPE ROCK MASS DUE TO FREEZE-THAW WEATHERING

高寒山区岩质边坡冻融风化破坏严重影响公路建设及其运行安全。为了揭示岩体在冻融条件下的破坏机理,本文通过对高寒山区岩质边坡现场调查、编录,结合室内试验及数值模拟等,从不同尺度下综合分析岩体的冻融破坏机理。室内试验显示岩块受冻融后存在强度弱化现象,其受控于岩块的结构构造、胶结程度及初始损伤裂隙发育情况;冻融试验揭示岩体裂隙发育特征对冻胀变形性质起决定作用,裂隙的冻融破坏速率远大于岩块,密闭条件下,裂隙水冻结成冰过程中形成冰劈效应,冻胀力可达33MPa以上;数值分析揭示了边坡温度场受低温、大温差影响最为明显,裂隙带受冻融影响严重,其为边坡冻融风化的通道,裂隙水冻胀形成冰劈是边坡冻融风化破坏的主要模式。

Severe damage of alpine mountain rock slopes due to frost-thaw weathering affects road construction and safe operation. This paper is to reveal the failure mechanism of rocks under freeze-thaw conditions. It is based on the site catalog of alpine mountain rock slope,and combined with laboratory experiments and numerical simulation. A comprehensive evaluation of freeze-thaw damage mechanism of rock is presented. Indoor experiments have showed that rock strength is weakened after freezing and thawing. It is controlled by the rock texture and structure,the degree of cementation and the initial fractures. The freeze-thaw tests reveal that development of rock fractures plays a decisive role in the nature of frost heave. The freeze-thaw damage rate along the fractures is far greater than the intact rocks. The process of fissure water frozen into ice forms the split effect. The expansion force can be reach to 33 MPa or greater.Numerical analysis reveals that the slope temperature field is affected by low and large temperature difference. Fractured zone is the most obvious area that is affected by freezing and thawing. It is the channel of slope freeze-thaw weathering.The congelifraction formed by fracture water frost heave is the main model of slope freeze-thaw weathering damage.