| More than 60%of China’s mineral resource reserves are distributed in the western region.With the further development of resources in the west,the slopes in the high-altitude cold regions are faced with complex freeze-thaw disasters.Repeated freeze-thaw cycles induce geological disasters such as landslides and subsidences on the slopes,which seriously threaten mine production and the safety of people’s lives and properties.A large number of rock bridges with high strength and concentrated stress exist in the slope body.Their distribution,development and stress state control the deformation of the slope.Therefore,the rock bridge plays a key role in the stability of the slope.The rock slopes with locked segment in the west of China are subjected to strong freeze-thaw weathering and faced with complex freeze-thaw disasters.It is a key and difficult problem for the prevention and control of slope disasters in cold regions to carry out the research on the deterioration and damage characteristics of rock bridge subjected to freeze-thaw cycles,and deeply reveal the mechanical mechanism of the failure evolution and sliding characteristics of the rock slope with locked segment from the perspective of micromechanics.This thesis investigated the damage characteristics and failure evolution law of fractured rocks obtained in slope of the Beizhan open pit in Xinjiang province exposed to freeze-thaw weathering by means of laboratory tests,theoretical analysis,similar model tests and numerical simulation.The stability and prevention measures of rock slope with locked segment in cold regions were put forward.The main contents are as follows:(1)The long-term frost heave pressure and frost heave deformation monitoring test of ice-saturated fractured granite with different lengths and opening degrees at different freezing temperatures was carried out through real-time monitoring system.The evolution characteristics of frost heave pressure and frost heave deformation during freeze-thaw process were obtained.In addition,the influence of freezing temperature and fracture geometry on the frost heave damage characteristics of fractured rocks was analyzed.Considering the characteristics of crack propagation and plastic strain of rocks,the frost heave deformation model of low temperature fractured rocks was established.The frost heaving deformation law of rock was obtained,and the frost heaving damage mechanism of low-temperature fractured rocks was revealed.(2)The mechanical tests of rocks under different stress paths was carried out,and the mechanical properties and failure mechanism of rock bridge subjedted to freez-thaw cycles were analyzed.In addition,the effects of freeze-thaw cycles,rock bridge inclination and confining pressure on the failure pattern of rocks were obtained.The acoustic emission parameters of fractured specimens exposed to freeze-thaw treatment were analyzed.The damage model of fractured rocks expericing freeze-thaw cycles based on acoustic emission parameters was proposed.Using the method of meso-damage theory and macro-statistical damage model,a macro-mesoscopic damage model of the locked rocks subjected to coupling action of freeze-thaw and loading was constructed,The damage and deterioration mechanism of the locked rocks with different rock bridge angles subjected to cyclic freeze-thaw was revealed.(3)Based on the similar physical test of the rock slope with locked segment,the digital image correlation system was used to collect the image evolution during the failure process.The evolution characteristics of the horizontal displacement field and the principal strain field of the locked slope subjected to freeze-thaw cycles were analyzed.Moreover,the influence law of freeze-thaw cycles and locked segment angle on slope deformation field is summarized.By analyzing the strain characteristics of the locked section in slope failure process subjected to freeze-thaw,the crack propagation process and failure mode of the rock slope with locked segment were obtained.Based on the multi-dimensional information collection of slope failure process,the failure precursor information of the rock slope with locked segment under the influence of freeze-thaw cycles was obtained.(4)The theoretical model of frost heaving deformation of fractured rocks was embedded in the PFC platform,and FISH program is compiled to calculate the frost heaving expansion rate of fractured rocks.The process of frost heaving damage of fracture was successfully simulated,and the change of meso mechanical field of frost heaving damage was analyzed.The rock block and joint were characterized by particle model and joint model respectively,and the particle flow model of intermittent jointed rock slope was constructed.From the perspective of mesomechanics,the mechanical mechanism in the progressive failure process of the rock slope with locked segment was deeply studied,and the breakthrough failure and sliding characteristics of the locked segment were obtained.In addition,based on the idea of weakening the meso mechanical parameters,the variation law of the safety factor of the rock slope with locked segment in cold regions was obtained.The corresponding reinforcement measures were put forward. |
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