非均质土体中盾构隧道开挖面支护力上限分析

Upper bound analysis for supporting pressure of shield tunnel in heterogeneous soil

基于对数螺旋破坏模式,考虑黏土的非均质特征,采用极限分析上限法推导了盾构隧道掌子面支护力计算公式,通过优化计算得到了不同条件下的最优上限解。采用该破坏模式与已有的模型试验、工程实例进行对比,验证了在非均质土中采用双对数螺旋极限分析上限法的适用性;同时详细分析了在土体不同参数条件下,隧道掌子面支护力、滑动面范围的变化趋势以及工程影响,结果显示在非均质土中,掌子面支护效率的主导因素是初始黏聚力与掌子面超前核心土,最后通过归一化处理得到了非均质土中极限支护力的设计推荐图,可为工程中初步确定盾构隧道掌子面支护压力提供理论依据。

Based on the logarithmic spiral collapse mechanism, and with considering the heterogeneity of clayey soil, the optimal upper bound solution of the face supporting pressure is obtained in heterogeneous soil in which the cohesive force varies linearly. The validity of the proposed solution is demonstrated by comparing the calculated results with the monitoring data and the results of model tests. In addition, the optimal supporting pressures and the logarithmic spiral sliding surfaces are analyzed in details for various soils. It is shown that in heterogeneous soils the soil cohesion and internal friction angle are the controlling factors. A design chart is developed for the limit supporting pressures in heterogeneous soils.