Upper Bound Solution of Passive Support Pressure Limit Analysis of Pipe Jacking Excavation Face in Clay Stratum

Setting reasonable slurry pressure in pipe jacking construction is the key to ensuring the stability of excavation face. If the slurry pressure is too small, it will lead to surface subsidence, and active instability will occur in severe cases. Excessive mud pressure will cause surface uplift and passive instability in severe cases, which will affect the safety of construction and surrounding structures. Based on the background of a water supply pipe jacking tunnel project in southwest China, the upper bound solution of passive limit support pressure of excavation face in clay stratum is derived theoretically, and the relationship between the upper bound solution of passive support pressure and the field slurry pressure is compared and analyzed. The influence of different buried depth and inner diameter on the passive support pressure was further studied. The results show that: (1) By comparing the upper limit solution of passive support pressure with the field mud pressure, the theoretical solution value is higher than the measured mud pressure, which can provide some reference for the reasonable setting of mud pressure in similar projects. (2) With the increase of buried depth, the passive support pressure increases linearly, the pressure ratio increases parabolically, and the increase rate decreases gradually. When the buried depth increases from 2 m to 10 m, the passive support pressure and pressure ratio increase by 456.6% and 59.1% respectively. (3) With the increase of inner diameter, the passive support pressure increases parabolically, and the increase rate decreases gradually. When the inner diameter increases from 2.0 m to 3.2 m, the passive support pressure increases by 5.6%.