Study On The Formation Mechanism And Its Engineering Application Of Broken Rock Zone In Deep Bedded Rock Mass

The formation characteristics of sedimentary rocks and the lithology differences between layers make the structural types of surrounding rock of coal mine roadway more complex,further leading to the formation,scope,shape and other characteristics of surrounding rock broken rock zone more complicated.Therefore,based on the supporting theory of broken rock zone of roadway surrounding rock,the theoretical solution of the loose zone was analyzed and reviewed in this paper from Mohr-Coulomb criterion,Drucker-Prager criterion and Hoek-Brown empirical strength criterion.Then,the “whole process simulation test system for structural instability of deep underground engineering”was adopted to design the six set of similar material model in the simulation experiment.Then "deep underground engineering structure instability of whole process simulation test system" was adopted to design six kinds of schemes of similar material model test,and the experimental results were compared and analyzed with the calculated results of 15 set of numerical simulation schemes,and the evolution and development mechanism of the loose circle after roadway excavation in layered rock mass and under deep high stress con ditions were studied.Finally,based on the above two aspects of research,the numerical simulation was adopted to design the support scheme,and a synergistic control method for large broken rock zones of crossing roadway in deep surrounding rock was proposed.Furthermore,the field engineering test has been carried out successfully and a good supporting effect has been obtained.The main conclusions are as follows:(1)In the theoretical calculation method of broken rock zone,the radius of broken rock zone calculated by M-C criterion and D-P criterion are smaller than H-B empirical strength criterion,and these three are generally smaller than the actual measured value.Therefore,the necessity of checking the calculated value of the broken rock zone with the field test value in support design is emphasized.The applicability of boundary conditions setting,rock strength softening method and non-circular section standardization in the analysis of surrounding rock loose zone of layered rock roadway are discussed.In contrast,the calculation of the surrounding rock plastic zone is more rigorous in theory.(2)The broken rock zone in the layered rock mass is characterized by a leaping cascade developmen.Meanwhile,its range and shape are controlled by the direction of the maximum principal stress,presenting the orthotropic characteristic,and Its axis of symmetry is perpendicular to the rock stratum and passes through the centroid of roadway simultaneously.When the lateral pressure coefficient is less than 1.0,the broken rock zone occurs at the top of the roadway first,followed by the two sides of the roadway,and the broken rock zone at the left-right sides is larger than that at the top-bottom of roadway.When the vertical direction of rock stratum coincides with the bottom angle bisector of roadway,the thickness of broken rock zone at the part of roadway bottom angle will increase significantly,while the influence of strata dip angle on the size and range of broken rock zone is not significant.(3)The weak interlayer in surrounding rock causes visible bias failure in the roadway and presents obvious asymmetrical deformation characteristics on the whole.The difference between the broken rock zone and the failure characteristics are obvious in each parts of the roadway.Thus,some measures should be taken to strengthen the support,such as adding and lengthening the bolts and cables.The results show that the support has a significant influence on the broken rock zone near the weak interlayer,but a weak impact on the part which is far away from the weak interlayer in the roadway.(4)The field test data show that the test roadway of the second level in Chengjiao Coal Mine has a large broken rock zone,and its surrounding rocks are characterized by soft rock,high stress and swelling.Moreover,due to the greater difference in principal stress,large deviatoric stress will be generated,which is the internal cause of poor stability of the roadway.The stability problem of crossing roadway with large broken rock zone in deep coal mine can be effectively solved by synergistic control technology of shotcrete and steel mesh,prestressed bolts and cables,combined with cooperative grouting.At the same time,it is supplemented by strengthening the reinforcement measures at the bottom corner of the upper side and the arch shoulder of the lower side in a local section of the roadway.There are 107 pictures,12 tables and 186 references in this paper.