Study on Loose Soil Pressure Calculation of Shield Tunnel Based on Linear Change of the Included Angle of Slip Surface
Given the fact that the slip surface form changes as the relative displacement changes,and with consideration of the evolution process of soil arch of shield tunnel under different ground losses,the method for calculating the linear change of included angle has been devised.The differential equation for the stress in ultimate equilibrium is analyzed in order to solve the loose soil pressure expression,and the impact of stratum arch on the boundary conditions is ana-lyzed by considering the pattern by which the slip surface height changes as the relative displacement changes.The particle flow numerical analysis simulation has been conducted to investigate the variation pattern of soil-arch ratio in different cases and thus verify the rationality of the theoretical calculation model.As the study indicates:Average vertical stress increases as depth increases,but the increase rate gradually decreases;the soil arch evolution process is dominated by stress restoration,soil-arch ratio slowly increases from 0.326 to 0.495;bigger buried depth ratio and internal friction angle entail smaller soil-arch ratio.
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