顶管隧道施工掌子面极限支护压力计算及影响因素研究OA

Based on limit equilibrium theory,a face instability failure model that explicitly accounts for stratified ground conditions is developed,and an analytical expression for the critical support pressure is derived.The formula is verified using a finite-element model calibrated to the pipe-jacked tunnel section of the Hefei segment of the Yangtze-to-Huaihe Water Diversion Project,with parametric analyses evaluating the influence of ground properties on the ultimate support demand.The results indicate that:(a)the critical support pressures predicted by the proposed formula differ from the numerical results by less than 10%,thereby validating the rationality of the model and calculation formula;(b)the deformation is more pronounced in the upper half of the face,and with the increase of internal friction angle,the sensitivity of the required support pressure to cohesion diminishes,and moreover,both the increases of the internal friction angle and cohesion will lead to a decrease in the ultimate supporting pressure;and(c)despite the larger stress release induced by increasing the cover-to-diameter ratio,the concurrent gain in soil strength leads to a progressive reduction in the normalized ultimate support pressure.