Research On Crack Evolution Mechanism And Large Deformation Control Of Surrounding Rock In Soft Rock Roadway

With the increasing depth of coal mining,broken soft rock roadway continues to appear in complex stress environment.This kind of roadway has the characteristics of surrounding rock crack development,large deformation,long deformation duration and fast deformation speed.Effectively controlling the deformation of this kind of roadway has become an urgent problem to be solved.In this thesis,using the research methods of laboratory test,theoretical analysis,numerical simulation and field test,with the research goal of effectively controlling the rheology of deep broken soft rock roadway,the large deformation mechanism of deep soft rock roadway is studied from the perspective of crack and energy,and the relevant control technology is deeply analyzed to control the rheology mechanism of roadway,A crack arrest and crack reduction control technology based on tension anchorage system and deep and shallow hole grouting is proposed.(1)Based on the uniaxial rheological test of sandy mudstone,its rheological characteristics are analyzed,rheological parameters are accurately identified and the relationship between each parameter and rheological characteristics is analyzed.According to the Mohr Coulomb criterion and the long-term and short-term strength relationship of sandy mudstone,the relationship between block strength and time is analyzed from the change of cohesion,and the number of yield areas in the block near the joints at different times are counted,and the relationship between joint strength and time is revealed,and finally the joint strength is constructed.The rheological model with variable attenuation and the matching of damage characteristics and strain characteristics verify the rationality of the model.(2)Based on the corrected mechanical parameters and the joint strength time-varying attenuation rheological model,a cracked rock mass model was constructed.The FISH language and energy module were used to monitor the crack propagation and energy evolution law during the time-varying strength of the rock mass.,Study the influence of crack characteristics on the damage and fracture of rock mass and energy storage capacity,and reveal the internal influence mechanism of rock deformation caused by the crack propagation process.(3)Based on the small range yield criterion and the effective shear stress formula,the relationship between the effective shear stress on the crack surface and its depth is studied.The results show that the effective shear stress on the surface decreases with the increase of the crack depth under rheological conditions.Therefore,the cracks in surrounding rock have the characteristics of shallow instantaneous initiation and deep delayed initiation.The calculation model of crack tip intensity factor of anchored surrounding rock is established,and the expression of intensity factor in the range of anchor length is obtained analytically.The analysis shows that the crack tip intensity factor after anchorage is not only related to the characteristics of the crack itself,but also affected by the rockbolt prestress,anchorage angle and the location of the crack in the anchor section of the rockbolt.(4)According to the rockbolt pull-out test results,the rockbolt element parameters in UDEC are corrected,and two typical randomly cracked rock masses are established by inversely using the relationship between rock cohesion and crack occurrence.The meso damage and energy accumulation and dissipation process of anchorage cracked rock mass are analyzed,and the prestressed crack arrest effect of anchorage structure is verified.The research shows that high prestress can effectively reduce the deformation and damage degree of cracked rock mass,improve the rock energy storage limit and shorten the long-term large deformation time.(5)The displacement,stress and crack evolution law of roadway surrounding rock are analyzed from the engineering scale,and the rheological characteristics of sustained large deformation of roadway caused by instantaneous crack initiation of shallow surrounding rock and delayed crack initiation of deep surrounding rock in soft rock roadway are revealed.The analysis results show that the instantaneous initiation of shallow cracks leads to the primary deformation of roadway surrounding rock,and the delayed initiation of deep cracks leads to the secondary long-time large deformation of roadway.(6)Based on the large deformation characteristics of the soft rock roadway,the support concept of crack arrest and crack reduction is proposed.Tension bolts and shallow hole low pressure grouting suppress the development of shallow cracks,reducing the number and propagation speed of cracks,reducing short-term deformation and deformation speed,and advancing the stability time of roadway deformation;deep hole high pressure grouting filling cracks increases the rock mass Completeness shortens the secondary deformation cycle.Industrial tests show that this kind of control technology effectively solves the problem of continuous large deformation of deep broken soft rock roadways.There are 169 pictures,28 tables and 220 references.