土压平衡式顶管施工中顶进支护压力是维持前部掌子面稳定的重要施工控制参数。在软黏土地层中考虑分段顶进和开挖土体受扰动强度折减,采用数值模拟分析顶进掌子面支护压力不足引起的前部土体主动破坏模式、塑性区发展、地层扰动以及土体应力释放,在此基础上进一步研究顶管隧道埋深、管径、土层性质和不同扰动强度折减等因素对极限顶进支护压力的影响规律。结果表明:(1)当掌子面顶进支护压力逐步减小时,前部土体呈现半梨形外鼓破坏模式;塑性区在一定范围内发展近似形成半椭球形;掌子面应力释放率逐步增大,但不同部位处的应力释放率存在差异,掌子面中心处应力释放率大于顶部和底部;(2)主动极限顶进支护压力随着埋深和管径增大而不同程度地增大;土层性质参数对极限顶进支护压力影响的敏感程度依次为内摩擦角、粘聚力和弹性模量,其中内摩擦角和粘聚力受扰动折减程度对极限顶进支护压力有较为显著的影响,弹性模量扰动折减则几乎无影响。 Soil pressure balanced jacking construction jacking support pressure is to maintain the stability of the front face of the important construction control parameters. In the soft clay stratum, the disturbed strength of subgrade excavation and excavation is taken into account. By using numerical simulation, the active failure mode of front soil, the development of plastic zone and the disturbance of formation And the release of soil stress. On this basis, further study is conducted on the influence of the factors such as the depth of buried pipe tunnel, the diameter of pipe, the nature of soil layer and the reduction of different disturbance intensity on the ultimate support pressure. The results show that: (1) The semi-ellipsoidal shape develops in the semi-ellipsoid in a certain range when the pressure on the top of the face gradually decreases, The rate of stress release at different sites is different, and the rate of stress release at the center of the facet is greater than that at the top and bottom; (2) The active limit jacking pressure varies with depth and diameter The degree of sensitivity of the parameters of soil layer to the ultimate support pressure is the internal friction angle, cohesion and elastic modulus, of which the friction angle and cohesion disturbance reduction extent to the maximum Into the support pressure has a more significant impact, the elastic modulus disturbance reduction is almost no effect.