| The horizontal layered rock mass is widely distributed in China,which is often encountered in engineering practice.In the long process of deposition,the layered rock mass is complicated due to the diversity of sedimentary environment and time,which leads to the obvious difference of interlayer bonding strength of layered rock mass,which provides difficulties for stability analysis and accurate grasp of support design parameters,and it is an economical and effective method for tunnel reinforcement.Therefore,the research on the bending deformation characteristics and anchoring effect of layered surrounding rock is of great significance to ensure the safety of tunnel engineering.The main research contents are as follows.(1)According to the different failure modes of tunnel roof with different interlayer bonding strength,the roof of horizontal layered cavern is qualitatively divided into two models:the roof with high interlayer bonding strength and the roof with low interlayer bonding strength.The calculation models of roof bending failure are deduced respectively,and the whole process of rock beam instability from fixed beam model to simply supported beam model in horizontal layered roof excavation is clearly described.(2)Based on the similarity theory and the principle of orthogonal experimental design,the ideal rock similar material was developed by uniaxial compression test and variable angle shear test of similar materials with different proportions by servo press.The direct shear test of bedding surface under different working conditions was carried out,and the grinding method of bedding surface with different interlaminar bonding strength was obtained.(3)Several groups of 500 mm×100 mm×100 mm horizontal layered rock beams were made for indoor model test.The mechanical characteristics,crack distribution,acoustic emission characteristics and bending strength of rock beams with hard structural plane and rock beams with soft structural plane under different interlayer bonding strength were studied by using acoustic emission monitoring and strain monitoring technology,and the correctness of the calculation model is verified.(4)By comparing the failure difference of horizontal layered rock beam before and after anchoring,the macro mechanical characteristics of anchored layered rock roof are analyzed,the quantitative influence of bolt reinforcement on deformation characteristics and strength parameters of rock mass is discussed,the anchoring mechanism of bolt on layered rock mass is revealed,and the influencing factors of anchoring effect of horizontal layered rock mass are obtained,The calculation formula of the optimal length of the bolt is obtained.(5)Taking a tunnel in Yunnan Province as an example,the solid model of the tunnel is established,and the shell element built in FLAC3D is used to simulate the concrete cover,and the cable element is used to establish the anchor model.The calculation of the initial ground stress field before the tunnel excavation and the length of the modified anchor support is completed,and the stress field,displacement field and the distribution of the failure area under the general anchor support are compared and analyzed.The applicability and reliability of the modified formula are proved.Aiming at the scientific problem of stability control of layered tunnel roof with different interlayer bonding strength,this paper deeply discusses the fracture evolution characteristics and anchoring effect of horizontal layered roof by combining theoretical derivation,laboratory test,numerical simulation and engineering practice,which provides theoretical guidance for tunnel construction and operation safety. |
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