A load mode suitable for shield tunnels in soft-hard heterogeneous ground was proposed,which systematically considered the relationship between tunnel depth,the form of slip surface,lateral pressure coefficient and the ground.For shallow tunnels,the lateral pressure coefficient and vertical loose earth pressure expression for the elliptical slip surface at ultimate limit state were deduced based on ellipsoid theory,and the mechanical equilibrium equation was constructed to derive the lateral pressure calculation formula.For deep tunnels,the width of slip surface in Terzaghi's theory was reasonably corrected considering the mutation of soft-hard heterogeneous ground,and the corresponding formulas of surrounding rock pressure were derived.Additionally,combined with two typical working conditions that the boundary of soft-hard heterogeneous ground is located above and below the horizontal middle line of the tunnel,the expression of the reaction force at the tunnel bottom was derived.Finally,the proposed load mode was verified by combining with engineering examples.The results show that compared with the load system of the modified routine method,the error between the vertical earth pressure at the top and lower half arch of soft soil-hard soil tunnels obtained by the proposed method and the measured value is reduced by 74％and 172％,respectively.However,compared with soft soil-hard soil tunnels,when this method is applied to soil-rock tunnels,the error between the calculated vertical earth pressure of the lower half arch and the lateral earth pressure at the tunnel bottom and the measured value is smaller.Namely,the proposed load calculation mode aligns better with actual tunnel loading conditions,particularly in scenarios with greater tunnel depth-to-diameter ratios and firmer lower ground,demonstrating its increased suitability.
关键词
盾构隧道/软硬不均地层/围岩压力/滑移面/荷载模式
Key words
Shield tunnel/Soft-hard heterogeneous ground/Surrounding rock pressure/Slip surface/Load mode
维普
万方数据