【摘要】 城市轨道交通越江盾构隧道施工时，上覆土层在土仓内、外水力交互作用下将产生渗流，渗流会改变隧道整体受荷状态进而影响其结构稳定性．为描述稳定渗流条件下盾构隧道外侧水土荷载变化规律，解决既有松动土压力计算中松动区渐进破坏与渗流效应考虑不全的难题，基于颗粒椭球体理论，探明了松动区发展与土体渐进破坏间的关系；基于水平微分单元法，推导得出考虑大主应力拱效应的侧土压力系数计算公式；进一步构建并验证了考虑松动区渐进演化过程的隧顶水土荷载的数值迭代算法，实现松动区发展到任意高度时的隧顶水土荷载计算．研究结果表明：主应力迹线形状系数随着土体内摩擦角和应力偏转角的增大而减小，当应力偏转角和土体内摩擦角确定时，抛物线拱形应力迹线引起的荷载不均匀分布最小；平均侧土压力系数随着土体内摩擦角增加呈现略微增大的变化规律；调用摩擦角随应力偏转逐渐发展，滑移面剪应力完全发挥时对应的盾构隧顶水土荷载最小；土体内摩擦角和黏聚力的增加将显著降低隧顶水土荷载，渗流的存在将削弱土拱效应进而增大隧顶水土荷载．本文成果为稳定渗流场中非极限状态松动土压力计算提供了更精确的解答，可为实际工程中水下盾构隧道受荷评价提供理论依据.更多还原

【Abstract】 During the construction of a cross-river urban rail transit shield tunnel,seepage will occur in the overlying soil layer due to the hydraulic interaction between the interior and exterior of the tunnel,thus changing its overall loading state and further affecting its structural stability. To describe the variations in water and soil loads on the outer side of shield tunnel segments under steady seepage conditions and to address the challenge of incomplete consideration of progressive failure and seepage effects in the existing calculation methods for loosening earth pressure,the relationship between the development of a loosening zone and the progressive failure of soil was explored based on the ellipsoidal particle theory. A calculation formula for the lateral earth pressure coefficient taking into account the major principal stress arching effect was derived using the horizontal differential element method. Moreover,a numerical iterative algorithm for water and soil loads at the tunnel crown considering the progressive evolution of the loosening zone was developed and validated,which enables the calculation of water and soil loads at the tunnel crown for any given height of the loosening zone development. The research results show that the shape coefficient of the principal stress trajectory line decreases with increases in the internal friction angle of soil and the stress deflection angle. When both the stress deflection angle and the internal friction angle of soil are fixed,the parabolic arching stress trajectory line causes the least uneven load distribution. As the internal friction angle of soil grows,the average lateral earth pressure coefficient also shows a slightly increasing trend. As the invoked friction angle develops gradually with the stress deflection,the water and soil loads at the shield tunnel crown are minimized when the shear stress along the slip surface is fully mobilized. The increases in the internal friction angle of soil and cohesion will significantly reduce the water and soil loads at the tunnel crown,while the presence of seepage will weaken the soil arching effect and therefore increase the water and soil loads at the tunnel crown. The results in this paper provide a more accurate solution for calculating the loosening earth pressure in a non-limit state under steady seepage conditions,offering a theoretical basis for the load evaluation of underwater shield tunnels in practical engineering.更多还原