Study On Anchorage Mechanical Mechanism And Application Of Rock Bolt In Composite Rock Mass

Bolt support technology has the advantages of high strength,good reliability,low cost,and strong adaptability,which is the primary method of surrounding rock control and disaster prevention in engineering fields such as tunnel traffic,slope reinforcement,water conservancy,and hydropower,and coal mining at present.The composite rock mass is a common sedimentary rock in engineering.As the depositional environment and other factors influence the composite rock mass,the mechanical properties of each rock stratum vary greatly and have distinct bedding planes,resulting in the anchorage performance of rock bolt in the composite rock mass being significantly different from that in the homogeneous rock mass.Therefore,it is of great theoretical significance and application value to study the stress distribution characteristics and anchoring mechanism of rock bolt in composite rock mass for the rock bolt support design and disaster prevention in practical projects.In this paper,theoretical and experimental research is carried out on the load transfer mechanism of rock bolt,anchorage bearing characteristics of composite rock mass and mechanical characteristics of rock bolt in composite rock mass under bed seperation action utilizing theoretical analysis,indoor tests,numerical simulation and engineering practice.The following innovative research results are achieved.(1)In view of the nonlinear mechanical characteristics and residual strength of the anchorage interface,the nonlinear shear slip model of the anchorage interface considering residual strength is established.The method to determine the model parameters is proposed,and the control law of the parameters on the model curve shape and the influence factors on the anchoring effect are analyzed.Based on the differential equations of rock bolt load transfer mechanics,the pulling out load transfer models of rock bolt in single-layer rock masses and composite rock masses are established by the load transfer method.A calculation program for the stress distribution of rock bolt in the single-layer rock mass and composite rock mass is developed on the Matlab software platform.The distribution characteristics of the axial force of rock bolt,interfacial shear displacement and interfacial shear stress can be calculated on the platform.(2)The damage morphology and nonlinear mechanical characteristics of anchorage interface in soft rock stratum and hard rock stratum are analysed by short indoor anchor pulling out tests.The nonlinear shear slip relationship of anchorage interface in soft rock stratum and hard rock stratum is obtained,which verified the rationality of the nonlinear shear slip model of anchorage interface considering residual strength.The anchorage pulling characteristics in the single-layer rock mass and composite rock mass are analysed by indoor rock bolt pulling-out tests,which verified the feasibility of the pulling load transfer analysis model and stress distribution calculation procedure of rock bolt for the single-layer rock mass and composite rock mass.(3)Based on the pulling out load transfer model and stress distribution calculation procedure of rock bolt in the single-layer rock mass and composite rock mass,the progressive failure process of anchorage interface in a single-layer rock mass with different anchorage lengths is analysed.The influence of lithological sequences,rock stratum thickness,location and number on the load transfer of rock bolt and the anchorage bearing capacity properties in the soft and hard composite rock mass is revealed.(4)The load transfer model of rock bolt under the bed separation action of composite rock mass is established.The mechanical equations and analytical solutions for the stress distribution characteristics of rock bolt based on the linear shear slip relationship at the anchorage interface are obtained.Using fish language to import the nonlinear shear slip relationship of the anchoring interface into Flac3 D simulation software is proposed.The evolution characteristics of the axial force and interfacial shear stress under the action of the separation are obtained.The influence of bed separation value,location and number on stress distribution characteristics of rock bolt is revealed.(5)Based on the nonlinear shear slip relationship at the anchorage interface,the optimization design method of composite roof roadway support parameters is proposed.Taking the top coal roadway in thick coal seam as the engineering background,the deformation and damage characteristics of the surrounding rock of the roadway are analysed.The optimal design scheme of the supporting parameters of the top coal roadway in a thick coal seam under dynamic pressure is proposed.The field application effect is good,verifying the validity and rationality of the optimization design method of composite roof roadway support parameters.Taking the top roof coal roadway support in a thick coal seam in Zhangcun coal mine as the engineering background,the reason for deformation and damage of the roadway surrounding rock are analysed,and the optimal design of roadway support parameters is proposed.The field application effect is good,verifying the validity and reasonableness of the optimization design method of composite roof roadway support parameters.There are 155 figures,19 tables and 194 references.