Sub-classification Of Silty Clay And Stability Evaluation Of Surrounding Rock In Harbin Metro

In the process of construction of mined tunnels in silty clay stratum in Harbin Metro,due to the poor regional applicability of the existing national technical specifications,the sub-classification criteria of the surrounding rock are lacking,and the parameters of the advance support are unreasonable,which leads to the disconnection between the design and the site construction,and the management confusion.Aiming at the engineering problem,based on theoretical analysis,field test,indoor geotechnical test and numerical calculation,the research on the engineering characteristics of Harbin Metro silty clay was carried out,and the sub-classification standard of silty clay suitable for Harbin Metro was established.Based on the theoretical model of the parameters of the elastic foundation beam,the stability evaluation of the surrounding rock is carried out.Based on the sub-sedimentary criteria and stability evaluation results of the surrounding rock,the optimization analysis of the'advanced support parameters is carried out,and some useful conclusions are obtained.(1)In view of the unclear understanding of the engineering mechanism of silty clay in Harbin Metro,based on the stability index of surrounding rock,the study on sub-classification of silty clay in Harbin Metro was carried out.Through indoor geotechnical tests,physical and mechanical parameters of soil are obtained-The physical parameters are grouped by correlation analysis and dimension reduction analysis.The relationship between physical and mechanical parameters is determined by grey correlation analysis,and the classification index is determined.Finally,based on K-means clustering analysis,the classification index is clustered to determine the surrounding rock parameters corresponding to each sub-classification,and combining the on-site construction records to determine the surrounding rock qualitative indicators.(2)Based on the mechanism of the leading ductile support,the stability evaluation of surrounding rock was carried out.The theoretical model of the double-parameter elastic foundation beam for leading ductile support was established.The stability evaluation of the excavation face was carried out under the action of the leading ductile.The safety of the tunnel and the lining structure was evaluated based on the convergence constraint method.The V class silty clay tunnel can still ensure the stability of the surrounding rock without leading ductile support.The leading ductile support is required to support the stability of the surrounding rock for the ?1 and ?2 class silty clay tunnel.The state of ?2 class rock is poor,and the surrounding rock displacement is large.It is necessary to use the advanced pipe roof reinforcement or deep hole grouting to ensure the stability of the surrounding rock.(3)Through field grouting test,field comparative test and numerical calculation,the optimization of advance support parameters for ?,?1 and?2 class silty clay tunnels is carried out respectively.Through experimental study,it is determined that the leading ductile support can be cancelled under ? class surrounding rock,and the layout range of leading ductile can be reduced to 90 degree by ?1 class surrounding rock,and the optimal length of the leading ductile is 3.0 m,the optimum spacing is 30?40 cm,and the advanced support of ?2 class surrounding rock can adopt deep hole grouting to ensure the safety of construction.