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基于村山氏极限平衡法和极限分析上限法研究了盾构隧道开挖面稳定性,推导了维持开挖面稳定的最小极限支护压力计算公式。类似于Terzaghi地基承载力的叠加原理,将极限支护压力表示为土体黏聚力、地表超载和土体重度三项贡献的叠加,并对各自影响系数进行了分析。分析结果表明,极限平衡法得到的黏聚力影响系数随土体内摩擦角增大而增大,随隧道埋深比增加而减小,地表超载和土体重度影响系数均随土体内摩擦角增大而减小,地表超载影响系数随隧道埋深比增加而减小,土体重度影响系数随隧道埋深比增大而增大。当内摩擦角较小时,极限分析法得到的三项系数与土体内摩擦角和隧道埋深比的关系表现出与极限平衡相同的规律,但当土体摩擦角达到一定值时,土体黏聚力和土体重度的影响系数则不再随隧道埋深比而变化,地表超载影响消失。极限分析法得到的极限支护压力及三项系数均低于极限平衡法,但更接近现有文献中的有限元数值模拟结果。
Based on the Munsan’s limit equilibrium method and the upper bound limit analysis method, the stability of shield tunnel excavation surface is studied and the formula of the minimum limit support pressure for maintaining the stability of excavation surface is deduced. Similar to the superposition principle of Terzaghi’s foundation bearing capacity, the ultimate supporting pressure is expressed as the superposition of three contributions of soil cohesion, surface overloading and soil mass, and their respective influence coefficients are analyzed. The results show that the Coefficient of Cohesion (CLC) obtained by the limit equilibrium method increases with the increase of the frictional angle inside the soil and decreases with the increase of the buried depth ratio of the tunnel. Both the surface overloading and the soil mass influence coefficient increase with the increase of the friction angle The influence coefficient of surface overloading decreases with the increase of tunnel depth ratio, and the influence coefficient of soil mass increases with the increase of tunnel depth-depth ratio. When the internal friction angle is small, the relationship between the three coefficients obtained by the limit analysis and soil internal friction angle and tunnel depth ratio shows the same law as the limit equilibrium. However, when the soil friction angle reaches a certain value, the soil viscosity The influence coefficient of cohesion and soil mass no longer varies with the tunnel depth ratio, and the effect of surface overloading disappears. The ultimate support pressure and the three coefficients obtained by the limit analysis method are lower than the limit equilibrium method, but more close to the finite element numerical simulation results in the existing literature.