Influence of Terrain Bias on Multi-arch Tunnel Supporting Structure and Surrounding Rock
To study the influence of terrain bias on the multi-arch tunnel supporting structure and surrounding rock during construction,and to obtain the key steps and control points of construction process,the field test was carried out based on a biased multi-arch tunnel project in Changsha city.First,the dynamic monitoring during whole construction process was carried out in terms of the surrounding rock pressure,the axial force of initial supporting steel arch,the axial force of second lining steel,the vault settlement,and the surrounding rock convergence.Meanwhile,the two-dimensional numerical analysis model,considering the actual engineering condition and construction sequence,was established by using Abaqus to simulate the two construction schemes of excavating the shallow buried side chamber first,and excavating the deep buried side chamber first.Finally,the internal force and deformation rule of surrounding rock and tunnel supporting structure were analyzed by combining the field monitoring data and numerical simulation results.The result indicates that the theoretical value of surrounding rock pressure in the left chamber area is about 35 kPa greater than the measured value subject to topographic deviation.The obvious deviation location is the right arch shoulder,where the theoretical and measured values of surrounding rock pressure are about 36 kPa greater than those at the left arch shoulder.The large values of steel arch frame axial force are observed at the shoulder and waist areas,which are 470 kN and 407 kN.The axial force of second lining reinforcement at the top and foot areas are large,reaching 23.31 kN and 16.46 kN.The axial force of second lining reinforcement are symmetrically distributed along the middle diaphragm.The deeper the tunnel is buried,the smaller the settlement value will be.Taking the middle diaphragm wall as the symmetry axis,except for the outer measurement points,the settlement value of each corresponding measurement point in the left chamber is greater than that of the right chamber by 5%-6%.For the biased multi-arch tunnel,excavating the deep buried side tunnel chamber first is conducive to controlling the supporting structure deformation and stress,ensuring the structure stability.
tunnel engineeringbiasfield testnumerical simulationmulti-arch tunnelinternal force of supporting structuresurrounding rock deformation
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