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对武汉市某超大型超深基坑10幅邻近地连墙跳跃式施工过程进行了三维有限差分数值模拟。数值模拟步骤依次为泥浆护壁成槽开挖、混凝土浇筑及混凝土硬化3个过程。泥浆护壁成槽开挖及混凝土浇筑分别采用常静液压力和变静液压力的方式加载,混凝土的硬化过程采用变弹性模量和泊松比的线弹性实体单元完成。数值计算结果与实测数据吻合较好。对单个跳跃式开挖过程墙上土压力的监测揭示了地下连续墙施工影响应力重分布的变化规律。模拟施工完成后10幅地下连续墙上的土压力值沿墙长度方向随静止土压力值上下波动,波谷出现在槽段连接处附近,波峰接近槽段中心轴,波动幅度大小与土体深度有关。分析表明,泥浆压力、混凝土灌注压力及土压力差值是影响墙后应力重分布波动幅度的主要原因,适当的泥浆重度及合理的注浆方式能避免土体扰动。
A three-dimensional finite difference numerical simulation was made on the leaping construction of 10 adjacent contiguous walls in a very large ultra deep foundation pit in Wuhan. Numerical simulation step followed by mud retaining wall into the trench excavation, concrete pouring and concrete hardening three processes. Slurry excavation into trenches and concrete pouring are carried out by using the normal hydrostatic pressure and hydrostatic pressure respectively. The hardening process of the concrete is completed by linear elastic solid elements with variable modulus of elasticity and Poisson’s ratio. The numerical calculation is in good agreement with the measured data. The monitoring of earth pressure on a single leaping excavation process reveals the variation of stress redistribution affected by the construction of diaphragm wall. After simulating the construction, the earth pressure values of 10 underground continuous walls fluctuated along the length of the wall with the value of the static earth pressure. The trough appeared near the joint of the trough segment and the peak was close to the central axis of the trough segment. The fluctuation amplitude was related to the soil depth . The analysis shows that the difference between the mud pressure, the concrete pouring pressure and the earth pressure is the main reason that influences the amplitude of the stress redistribution after the wall. Appropriate mud weight and reasonable grouting method can avoid soil disturbance.