Damage Mechanism Of Strong-moderately Weathered Siliceous Slate With Coupled Effect Of Water Absorption And Engineering Disturbance

The deformation of surrounding rock is affected by the structural effect of rock mass.Unnecessary casualties and property losses may occur due to the unsafe state of surrounding rock during the excavation of Jiuzhai Tunnel.In general,previous studies can not simulate the actual excavation of the tunnel completely.The mechanism of dynamic failure and damage of tunnel surrounding rock under the change of water absorption strength of tunnel slates and engineering disturbance has not been fully understood and recognized,which leads to the lack of reliable basis for supporting design and deformation control of tunnel surrounding rock,and it is difficult to effectively control the stability of tunnel surrounding rock.This article through relying on the seventh Bureau of China Railway Yuchu project department TJ4 standard jiu zhai tunnel project.Theoretical analysis mainly includes rock mechanics and damage mechanics,field exploration,laboratory test with appropriate samples,and numerical simulation are used to summarize the mechanism of moderately weathered siliceous SLATE under water absorption and softening.Major progress has been made as follows:1.The water absorption characteristics of rock were tested,and the water absorption process of rock under different soaking time of SLATE was obtained.The water absorption process of SLATE can be divided into three stages according to the different amount and rate of water absorption.The second slow water absorption stage is the main water absorption stage of SLATE.2.The strength test of rock shows that the uniaxial compression strength of SLATE decreases with the increase of water content,and the elastic modulus also decreases.The failure mode is bicone shear failure.3.The failure state of rock during uniaxial compression is reproduced by numerical simulation software,and the change of the failure state inside the rock during the failure process is reproduced.The failure mode is consistent with the actual test.4.Through microscopic tests,the internal damage change process and damage mechanism of slates after water absorption are revealed.After the slates meet with water,the clay minerals expand,resulting in the expansion force,which greatly reduces the internal cohesion of the slates.To a certain extent,it is mainly manifested as the softening of the rocks and the decrease of the strength.5.Taking the damage dynamics and statistics theory of SLATE as the research basis,the appropriate damage model is selected according to the previous research results,and the engineering disturbance of rock is simulated through impact load experiment to obtain the damage evolution law of rock when it is disturbed in the engineering.