Deformation Failure Law And Control Measures Of Surrounding Rock In Soft Rock Roadway

With the rapid development of China ’s economy,the demand for coal is increasing year by year,and the mining depth is also increasing.Soft rock roadways appear in complex stress environments.Due to its own lithologic characteristics,the soft rock roadway is difficult to support,which seriously restricts the safe and efficient production of the mine.Effective control of such roadways has become an urgent problem to be solved.Therefore,it is of great significance to carry out in-depth and systematic research on the instability characteristics of surrounding rock in soft rock roadway.In this paper,the deformation and failure law of surrounding rock in soft rock roadway is deeply analyzed by means of theoretical analysis,numerical simulation,physical model test and field engineering test.Based on the elastic-plastic theory,the mechanical model of soft rock roadway surrounding rock under unequal pressure is established according to the softening characteristics of roadway surrounding rock.The softening parameters are introduced to derive the radius formula of plastic zone in soft rock roadway.Through theoretical analysis,the formation and evolution of plastic zone in soft rock roadway are discussed.It is found that the geometric shape and expansion range of plastic zone in soft rock roadway are affected by buried depth,roadway section type and lateral pressure coefficient.The relationship between the influencing factors of plastic zone in soft rock roadway and the stability of surrounding rock is studied.The deformation and failure process of plastic zone in soft rock roadway is monitored by numerical simulation.It is found that the larger the buried depth is,the wider the range of plastic zone is.From the comparison of the plastic zone of the three section types of circular,rectangular and straight wall semi-circular arched roadways,it can be seen that compared with the rectangular and straight wall semi-circular arched roadway section types,the plastic zone area of the circular roadway is smaller.Therefore,in the case of other factors unchanged,the plastic zone area is circular < straight wall semi-circular arch < rectangular.Therefore,the circular roadway is adopted in the engineering practice,which is beneficial to the stability control of the surrounding rock.When the buried depth is large,the plastic zone expansion form of rectangular and straight wall semi-circular arch gradually becomes circular,indicating that the influence of section shape on the plastic zone of soft rock roadway is gradually reduced.The numerical simulation of different lateral pressure coefficients shows that the area of Through the numerical simulation of the plastic zone of soft rock roadway under the influence of lateral pressure coefficient,it is found that the plastic zone area of soft rock roadway under different lateral pressure coefficients shows a certain regular change,that is,the horizontal stress of the roadway is continuously improved,and the plastic zone of soft rock roadway is gradually transferred from the two sides of the roadway to the roof and floor.The range of plastic zone of roof and floor increases with the increase of lateral pressure coefficient,and the range of plastic zone at two sides decreases with the increase of lateral pressure coefficient.When the lateral pressure coefficient λ is not equal to 1,the plastic zone presents a ’ butterfly ’shape development trend.The above analysis results provide a more scientific and reasonable basis for the optimization design of support.The similar physical model test method was used to carry out in-depth study on the deformation and failure law and mechanical properties of weak surrounding rock in circular roadway under the condition of confined uniaxial classification.During the test,the threedimensional full-field strain measurement system,high-definition camera and acoustic emission positioning monitoring system were used to monitor the displacement field,surface crack and internal crack evolution of roadway surrounding rock in real time.The results show that with the action of pressure after excavation,the displacement field of surrounding rock surface is symmetrically distributed in a form of oblique ’ X ’ in a circular roadway.The bearing capacity of rock mass at the junction decreases,accompanied by the generation of fine cracks on the surface of surrounding rock and the formation of macroscopic slip cracks.With the increase of pressure,the slip cracks gradually intersect and penetrate into the ’ V ’ shear wedge.The gap caused by the deformation of the wedge is one of the main causes of instability and failure of soft rock roadway.In the constant load stage of the model test,with the increase of time,the surface cracks and internal AE event points of the surrounding rock gradually spread to the deep part,and the fracture range gradually expands,indicating that the deformation process of the weak surrounding rock is not affected by the outside world.It has a strong time dependence,so it is very important to consider the time factor condition for the reasonable support of soft rock.By discussing and analyzing the stability control principle and key support technology of surrounding rock in soft rock roadway,taking the W3101 coal seam transportation gateway of Xiao kang Coal Mine as the engineering background,a combined support of ’ grouting anchor cable splitting grouting + bottom angle steel pipe grouting ’ + ’ anchor cable + diamond net ’ +’ U-shaped steel shed + wall thickness grouting ’ is proposed.Through the displacement monitoring results of the roof of the roadway,it is concluded that the settlement of the roof and two arch shoulders of the soft rock roadway is reduced.The deformation of the surrounding rock of the roadway during the service period meets the needs of coal mine safety production,reduces the maintenance cost of the roadway,and ensures the safe use of the roadway during the service period.