| Composite roof widely exist in coal mines in China.Composite roof is mainly composed of hard and soft rock layers.In the double layer composite roof,the deflection of the lower strata is larger than that of the upper strata,and the cohesive force between layers is small and easy to separate.It is easy to lead to roof caving accident due to the excessive amount of bed separation,which seriously affects the production safety of coal mine.The existing roadway support is generally designed by engineering analogy method,without considering the influence of rock structure on anchorage stress diffusion,and there is the phenomenon of excessive support.In order to reveal the bolt anchoring force in the distribution and diffusion rule of composite roof,optimization of composite roof bolt support parameters,this paper adopts theoretical analysis,numerical simulation and field test,the research methods of combining with double layer composite roof strata as the research object,the system study of the surrounding rock anchorage parameters and roof conditions on the influence of anchorage stress diffusion,It provides the basis for the determination of anchoring parameters under the condition of composite roof.The main work and achievements of this paper are as follows:(1)Based on the stress diffusion effect and the Boussinesq solution,the anchor force diffusion model and the viscous anchor force diffusion model were established respectively,and the stress diffusion model of composite roof bolt and composite roof inclined bolt were combined to form the stress diffusion model,and the accuracy of the model was verified.Studied by anchor and composite roof strata parameters on the diffusion rule of the stress in surrounding rock,the results show that :The anchorage stress in surrounding rock anchorage stress along the vertical direction present "to the" two pressure pull stress diffusion pattern of the anchorage stress along the horizontal direction as a whole shows the stress diffusion pattern of "symmetric decrease";The increase of preloading force does not change the diffusion pattern and law of anchorage stress,and the influence of stress diffusion effect.The value of anchorage stress at the same position increases proportionally with the increase of preloading force.With the increase of the bolt length,the diffusion range of the overall compressive stress in the anchorage range increases,but the overall compressive stress value decreases,and the anchorage stress value on both sides of the rock interface increases first and then decreases.With the increase of the length of anchorage section,the range of compressive stress decreases and the value of anchorage stress increases.As the range of tensile stress increases,the value of anchoring stress decreases,and the anchoring stress on both sides of rock interface increases and first decreases to tensile stress.In the case of not considering the shear action of bolts,from the Angle of anchoring stress diffusion,the middle end of composite roof anchoring is superior to the full-length and extended anchoring.With the increase of the elastic modulus ratio,the anchorage stress in the lower strata increases,and the anchorage stress in the upper strata decreases.(2)Based on the key strata theory and compound roof bolt anchoring force diffusion model,established the overburden of immediate roof and upper strata of load calculation model of immediate roof and upper strata,bolt anchoring force load calculation model of two sub models,combined with the beam bending theory deduced the row spacing between composite roof bolt design optimization model,and validates the feasibility of the model.As the anchors rise,the main design of the column,the distance between them.Composite roof stops shall be increased linearly by increasing the length of the straight line lightning bolts of the composite roof to be reduced first,then the parabolic model shall be increased by increasing the length of the anchorage section.The roof bolts of the compass are lowered,first of all.Increase the parabolic model by increasing the width of the road,the path of the line between them.The grounding of the assembled roof is roughly reduced in logarithmic rules by increasing the intermediate ratio.Direct roof and upper layer,distance between the composite roof cabling increases exponentially by increasing the thickness ratio between the roof is straight and the last plane is spaced between the composite roof doors increases exponentially,the level of lightning options and the roof parameters on the distance between bolts: Design anchorage force >thickness ratio > elastic modulus ratio > anchorage length > bolt length >roadway width,when optimizing the support design,the main consideration is to change the size of the anchoring force,and the length of the bolt and the length of the anchoring section should be reasonably set according to the conditions of the roof rock.(3)In light of the engineering background of the Niangyang mines,there can be a reduction in anchor length based on the optimal model for the design of anchors installed for anchors: d ?1143mm;in conjunction with engineering expertise,the initial optimization level of lateral design design in the test corridor has been achieved,and based on numerical simulation software calculations,the initial optimal design program can control rock stability in the test corridor during extraction and extraction.The test pavement support is optimized and the pavement stability is monitored in real time.In the influence stage of tunnel construction,the optimized scheme has a good effect on the control of rock stability around the pavement.Compared with the original scheme,the optimized scheme greatly reduces the consumption of bit technology and supporting materials,and greatly improves the efficiency of the tunnel. |
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