Differentiated Design and Construction of Inclined Shaft Top Picking Affected Section in Steeply Dipping Thin Slate Tunnel
To address the construction difficulties of inclined shaft top picking collapse in tunnel A of a high speed railway,this paper analyzes the specific working conditions and collapse causes of the inclined shaft top picking affected section,and forms a differentiated design and construction scheme for the inclined shaft top picking affected section:(1)During large-mileage construction of the main tunnel,before removal of pilot tunnel columns,advanced small conduits shall be constructed along the opposite direction of rock stratum inclination,with length L≥Hsin34°/sin(56°-a)+1;(2)The collapse section shall be treated by excavation from small pilot tunnel to small mileage to complete the pipe shed workshop;after the advanced pipe shed support is completed,the large-mileage construction of the main tunnel shall be carried out;(3)Ⅴa-type support is adopted for large mileage of main tunnel,and Ⅳb-type support is adopted for small mileage.By using differentiated design and construction parameters in the same stratum,this paper improves the technical economy of the scheme and solves the construction safety problem of the inclined shaft top picking collapse section.
tunnelinclined shaft top pickingsteeply dippingthin slatesmall pilot tunnelmain tunnel
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