Study On Deformation And Failure Mechanism Of Surrounding Rock In Deep Roadway With Reserved Floor Method

For a long time,coal has been the main resource of primary energy in China.However,with the gradual reduction and depletion of shallow resources,the main mines in central and eastern China gradually enter the stage of deep mining.The contradiction between high stress and low strength of deep surrounding rock is the main reason why the stability of roadway is difficult to control.In order to realize the stability control of roadway surrounding rock,the theory and technology of surrounding rock control considering internal rock action should be considered on the basis of mastering the disaster mechanism of large deformation of surrounding rock to control the evolution of surrounding rock fracture damage area,so as to solve the contradiction between high stress and low strength of surrounding rock.Reserved floor method has been used in some mining areas,and has achieved good support effect.In essence,it belongs to a special form of reserved internal rock excavation method.At present,few studies focus on the control effect of internal rock on surrounding rock stability.The paper is taking the roadway of Guqiao mining area in Huainan as the research background,the laboratory test,theoretical analysis and FLAC3D numerical analysis methods are adopted,the full-face method and reserved floor method are systematically studied.Under different excavation methods,the stress evolution laws of key points such as axis,vault,floor,wall and spandrel of surrounding rock face are analyzed,and the evolution characteristics of stress magnitude and stress direction of key points are analyzed quantitatively.Then the failure evolution laws and characteristics of surrounding rock with reserved floor method are analyzed and summarized from different angles such as stress path,displacement change and plastic yield zone,and the support design scheme of reserved floor method is studied.Combined with the stability control theory of surrounding rock in deep roadway,the corresponding support design scheme is put forward.The main results are as follows:(1)For the axis monitoring point,under the two excavation methods,the maximum principal stress ?1 and the minimum principal stress ?3 tend to be stable,and the magnitudes of ?1 and ?3 are 20.1 MPa and 2.7 MPa respectively under the full-face method;Under the reserved floor method,the upper section is excavated first,and after the lower section is excavated,the magnitudes of ?1 and ?3 are 4.0 MPa and tending to 0 MPa,respectively.For other key points,the difference between the maximum principal stress ?1 and the minimum principal stress ?3 tends to be stable.(2)The deformation and failure mechanism of surrounding rock under the excavation of deep roadway with reserved floor method is revealed.In the case of reserved floor method,the upper section is excavated first and the lower section is excavated later,so the failure zone of the floor is mainly shear failure;For the vault and wall,the shear and tension failure zone is mainly formed,and the shear stress concentration zone is mainly formed in the surrounding rock of the spandrel and foot.However,in the case of full-face excavation,the failure zone of roadway floor is mainly shear and tension failure;the failure area of vault,spandrel,wall and footings is the same as that of the reserved floor method.The surrounding rock of vault and wall forms the failure area dominated by shear and tension,and the shear stress concentration area dominated by shear failure is formed in the spandrel and footings.(3)Compared with the full-face method,the plastic zone of the roadway floor under step method is obviously smaller.The plastic zone of the roadway floor under full-face method extends down to about 3m,while the plastic zone of the roadway floor under reserved method extends down to about 2m.The lower section has a certain protective effect on the surrounding rock of the floor.(4)For the floor monitoring points,the maximum principal stress under the reserved floor method is rotated from the initial parallel roadway axis direction to the horizontal direction perpendicular to the roadway axis.After the application of the support scheme,the maximum principal stress direction remains unchanged,the surrounding rock structure is stable,the surrounding rock displacement is within the allowable deformation range,and the distribution range of the plastic zone around the roadway is relatively reduced,The roadway floor reinforcement has achieved good supporting effect.(5)Analyze and process the measured data through on-site measurement work.According to on-site monitoring data,two months after the implementation of the plan,the supporting structure fully played its role,the level convergence and the vault subsidence tended to stabilize,indicating that the stability of the surrounding rock is effectively controlled and the supporting plan is economical and reasonable.Figure[59]table[6]reference[80]...