Non-Uniform Failure Mechanism And Stability Control Of Mining Roadway Under Deviatoric Stress Field

The problem of surrounding rock failure and stability control of mining roadway has been a hot research field of roadway support engineering and disaster prevention,which is directly related to the safe and efficient development of coal resources in China.In recent years,with China’s coal development pattern gradually shifted from the central and eastern to the central and western regions,the mining depth is gradually extended to the deep,and the mining scope and intensity are increasing year by year.Due to the high-intensity resource exploitation,the stress environment of the roadway is complex and changeable with the spatial distribution,and the surrounding rock of the roadway is frequently affected by mining.At the same time,it is affected by the periodic fracture and blasting of the overlying strata in the production process,as well as the unfavorable factors such as geological faults,collapse columns,spontaneous combustion of coal seam and unreasonable production layout.As a result,the surrounding rock of the roadway is always affected by the high-biased stress environment formed by the superposition of mining stress.The stability of the surrounding rock of the roadway is further deteriorated,and the obvious stress concentration appears,showing the non-uniform large deformation and failure characteristics of the surrounding rock of the deep roadway.The existing roadway support theory and technology cannot well adapt to the surrounding rock support of mining roadway under high deviatoric stress field,resulting in difficulties in roadway maintenance,serious hidden dangers in safety production and serious harm to the safety of personnel.Therefore,it is of great significance to study the non-uniform failure mechanism and stability control of mining roadway under partial stress field for the protection of mine safety production and life and property of personnel.In this thesis,the comprehensive research methods such as field investigation,theoretical analysis,numerical simulation,laboratory test and field industrial test are used to master the distribution characteristics of non-uniform deformation and failure of surrounding rock of roadway under the influence of mining.The distribution law and relationship between deviatoric stress tensor J₂and plastic zone are studied,and the distribution characteristics of deviatoric stress field and the evolution law of plastic zone of mining roadway are obtained.The mechanical mechanism of the formation and expansion of plastic zone of surrounding rock of mining roadway under deviatoric stress field is revealed.The control idea of surrounding rock of mining roadway under deviatoric stress field is proposed,and the surrounding rock control technology of mining roadway under deviatoric stress field in Yangchangwan Mine is formed,and the field engineering test is carried out.The main conclusions and innovations are as follows:（1）The distribution characteristics of non-uniform deformation and failure of roadway surrounding rock under mining influence are obtained.The surrounding rock of mining roadway is frequently affected by mining under the deviatoric stress field,and there are obvious high deviatoric stress and stress concentration in the surrounding rock of roadway.The surrounding rock of roadway shows the non-uniform large deformation and failure characteristics of the roof failure depth in the coal wall side is greater than that in the coal pillar side,the two sides of the drum are serious,and the floor failure depth in the coal pillar side is greater than that in the coal wall side.（2）The analytical formula of J₂at any point around the roadway under partial stress field is derived.The second invariant J₂of deviatoric stress tensor is introduced to characterize the failure of surrounding rock of roadway.Based on the elastic-plastic theory,the analytical formula of J₂at any point around circular roadway under deviatoric stress field and the analytical formula of J₂when stress deflection occurs are derived theoretically.（3）The distribution law of J₂stress field in roadway surrounding rock and the relationship between its distribution form and plastic zone form are obtained.The J₂stress field of roadway surrounding rock under different stress environment has three distribution forms of’circle’,’ellipse’and’butterfly’,and the J₂stress field has one-to-one correspondence with the distribution form of plastic zone.That is,when the J₂stress field of roadway surrounding rock presents the distribution forms of’circle’,’ellipse’and’butterfly’,the corresponding plastic zone of roadway surrounding rock also presents the distribution forms of’circle’,’ellipse’and’butterfly’.（4）The relationship between the direction of J₂stress field and the direction of plastic zone is obtained.Under different stress environments,when the principal stress deflects over a certain angle,the J₂stress field and the plastic zone also deflect over the same angle,which has a one-to-one correspondence.（5）It is concluded that there is a one-to-one correspondence between the surrounding rock J₂and the plastic zone in the shape and direction under the partial stress field.Based on the dynamic distribution characteristics of J₂in mining roadway and the evolution law of surrounding rock plastic zone under deviatoric stress field,when the roadway is in different mining influence positions,the J₂shape of surrounding rock of roadway evolves from uniform distribution’oval’to non-uniform distribution’butterfly’,and the corresponding plastic zone of surrounding rock of roadway also evolves from uniform distribution’oval’to non-uniform distribution’butterfly’,and the plastic zone of surrounding rock deflects in the same direction and angle with the deflection of J₂stress.（6）It reveals the non-uniform failure mechanism of mining roadway under partial stress field.Affected by the superposition of supporting pressure,original rock stress and mining stress in the lateral goaf,the surrounding rock of the mining roadway is in a high deviatoric stress environment.The J₂stress field of the surrounding rock of the roadway shows a’butterfly’non-uniform distribution,which causes the’butterfly’non-uniform plastic zone of the surrounding rock of the roadway.The stress field will rotate under the influence of the goaf,resulting in the rotation of the plastic zone of the surrounding rock of the roadway.When the J₂butterfly leaf is deflected to the vicinity of the roof of the roadway,it will lead to uneven plastic expansion of the roof,which may lead to roof leakage and roof caving.When the J₂butterfly leaf is deflected to the two sides of the roadway,it may lead to serious bulging of the side and shrinkage of the roadway section.The plastic zone of roadway surrounding rock presents’butterfly’non-uniform expansion,resulting in non-uniform failure characteristics of roadway surrounding rock.（7）The surrounding rock control principle of mining roadway under deviant stress field is put forward.The control idea of surrounding rock of mining roadway under deviant stress field is put forward from three dimensions of regulating J₂stress concentration of roadway surrounding rock as a whole,coordinating strengthening support of asymmetric long and short anchor cable in local section and advanced high strength yield support in key areas.（8）The surrounding rock control technology of mining roadway in Yangchangwan Mine was formed.From the perspective of controlling the caving of the broken zone of the surrounding rock of the roadway,based on the proposed control idea of the surrounding rock of the mining roadway under the partial stress field,and combined with the actual mining situation of 160206 working face in Yangchangwan Mine,the surrounding rock support technology of the mining roadway under the partial stress field in Yangchangwan Mine was proposed,namely,the advanced roof deep hole pre-splitting blasting pressure relief+the asymmetric long and short bolt（cable）coordinated strengthening support+the advanced pressure support of the pumping pillar and the non-repeated support unit support,and the field industrial test was carried out.（9）Field engineering test results showed that the roof deep hole pre-splitting blasting control the J₂stress form,using asymmetric length of anchor cable inhibits the plastic zone is butterfly malignant expansion,the pillar and without repeated support pumping unit scaffold eliminates the focus area roof caving,the deformation of roadway roof effectively reduce,efficient production to protect the safety of the working face.