Study On Characteristics And Degradation Damage Mechanism Of Slope Rock Mass Under Freeze-thaw Cycles

With the steady advance of the grand blueprint for the development of western China,a large number of rock projects have been built in the high and cold mountainous areas.Affected by extreme temperature difference,rainfall,snowfall and other factors,the rock mass of the project shows obvious freeze-thaw damage phenomena,which leads to frequent geological disasters,seriously endangers the safety of people’s lives and property,and also restricts the progress of the project construction.Therefore,it is of great significance to study the mechanism and evolution of freeze-thaw damage of rock mass in combination with the specific characteristics of the project.This paper takes the left bank slope of QBT water Conservancy project in Altay,Northern Xinjiang as the research background,and selects typical quartz schist and granite of the left bank slope.With the freeze-thaw cycles as control condition,carried out a series of physical and mechanical properties test,studied the evolution regularity of physical mechanics parameters,and to the left bank slope for the prototype was carried out by the freeze-thaw environment dipping fractures slope failure model test,and by using RFPA2D-Thermal software explores the negative temperature fissure and mechanical response of slope rock mass under the condition of mechanism.In addition,the feasibility of two kinds of fiber concrete as slope antifreeze material is studied.The main research contents are as follows:(1)The article carried out uniaxial and triaxial compression tests on quartz schist and granite under different freeze-thaw cycles.The variation rules of compressive strength,elastic modulus,cohesion and internal friction angle under different freeze-thaw cycles were clarified.Based on the stress-strain curve of the whole process,the compression deformation characteristics before and after the freeze-thaw cycle are analyzed,the damage deterioration constitutive model of rock is established,and the evolution rules of damage amount and damage evolution rate are analyzed.(2)In this paper,the macroscopic transfixion mode of rock compression failure is studied by different research methods.,and the effects of freeze-thaw cycle,schistosity structure and confining pressure on the macro breakthrough mode of rock compression are summarized.Based on the analysis of the triaxial compression failure mechanism of freeze-thaw flaky rock,a prediction model of the triaxial compressive strength of the inclined flake quartz schist is established,which takes into account the number of freeze-thaw cycles,the inclination Angle of the flake plane and the confining pressure.(3)Based on the similarity theory,the physical model test of indoor joint slope failure under freeze-thaw environment was established,and the laws of temperature field,frost heaving force,slope deformation and crack expansion in the test process are obtained.The relationship between frost heaving force and slope deformation and crack expansion is established.With the help of RFPA2D-Thermal software,the failure process of frost swelling and its failure mechanism were reconstructed.(4)The physical and mechanical properties of polyacrylonitrile fiber reinforced concrete and polyacrylonitrile fiber steel fiber reinforced concrete during freeze-thaw are studied.The feasibility of the fiber as antifreeze material of slope was evaluated and the optimal volume ratio of fiber was proposed.The conclusion of this study can provide guidance for the construction and protection design of slope engineering similar to those in alpine mountainous areas.