The Rock Degradation Damage Characteristics And The Disaster-Causing Effects Under The Cyclic Freeze-Thaw Action

With our country vigorous development and construction of infrastructure in the western region, the problems of freeing-thawing action in many large rock engineering constructions in alpine mountains are more and more concerned by relevant scholars. In this case, Research the physical and mechanical behavior of rock mass under freeing and thawing condition is especially important. The article based on three typical collapse slopes along the Tianshan road. Investigated and analysed the effects of rock slopes stability in the congelifraction environment of the Tianshan mountains. Through the cycles of freeing and thawing test for three typical rocks, more in-depth researched the physical and mechanical degradation damage mechanism of the different kinds of rock under the freeing and thawing condition, and analysed their freeze-thaw failure mode. Summarised and put forward two different freeze-thaw degradation modes for them. Fitting obtained the relational expression of their uniaxial compressive strength and structural plane shear strength with the numbers of freeze-thaw cycles. Preliminary quantified the influence of the cyclic freeze-thaw action to rocky mechanicial parameters. And applicated it in the UDEC to calculate the stability of the collapse slopes. In-depth analysed the evolution law of their stress, displacement and stability, and their unstable modes. Summarized the disaster-causing effects that under the cyclic freeze-thaw action in alpine mountains.The main research results of this article are as follows:(1) Through survey and analyse the geological environment conditions of Tianshan road that belongs to alpine mountains, find the rock slope stability is not only restricted by the landform, the strata lithology, the neotectonic movement, its own slope structure features and human engineering activities, but also affected by the unique congelifraction environment which is the inducting factor of geological disasters such as collapse.(2) Granite, sandstone and phyllite due to mineral composition, degree of consolidation, the moisture content and other factors, leading to their change law of physics and mechanics under the cyclic freeze-thaw action are different. For the granite, sandstone and other hard rock, the main failure is their interal crack propagation. For the phyllite and other soft rock, the main failure is their particle precipitation. Hereby put forward two degradation modes of freeze-thaw action.(3) Based on the three kinds of rocks uniaxial compressive strength test and structural plane shear strength test, fitting obtained the mechanical strength attenuation formula under the action of freezing and thawing. Analysed their attenuation features. Summarized the freeze-thaw strength effect coefficients and freeze-thaw coefficients. And it is worth pointing out that the pre-freeze-thaw cyclic action on rock mass strength is significant and then tends to be gentle.(4) In the freeze-thaw effect area of slope rock mass will appear destructive shear stress under the cyclic freeze-thaw action. With the freeze-thaw action goes on, the destructive shear stress concentration area will gradually expand and ultimate perforate and form failure surface. Cause slope instability.(5) Slope stability (factor of safety) will fall significantly and then tend to be gentle. The maximum displacement of slope is contrary. Because the attenuation of rock mass, modulus, etc. The maximum displacement of slope will increase smoothly at the early stage of the freeze-thaw cyclic action. With the slope stability (factor of safety) decreases, especially when they are on the verge of destruction (limit equilibrium state), the slope displacement will increase sharply.(6) Slope instability first occurs in the destructive shear stress concentration area. Then, as the leading edge of the slope rock mass destruction causes the trailing rock mass free and further failure. It is a progressive failure process.