半封闭地下空间中盾构掘进对土体的扰动分析

Analysis of Soil Disturbance Caused by Shield Tunneling in Semi-Enclosed Underground Space

为分析半封闭地下空间中盾构掘进对周围土体及结构的影响,以上海市轨道交通7号线某盾构区间侧穿地下连续墙为背景,进行了现场数据监测及三维有限元数值模拟.研究结果表明:地下连续墙在束缚了土体侧向位移的同时,盾构掘进使软土向隧道侧产生位移,并增大了土体的竖向位移;在盾构掘进过程中,地下连续墙所围半封闭空间体内土体中土压力近似正态分布,超孔隙水压力先增后减,且由于地下连续墙的挡土效应,它们的积聚过程加剧、消散过程减缓;超孔隙水压力的升降会显著影响到邻近地下结构的安全,通过调控注浆压力、盾构掘进速度和布设砂桩等措施,可有效减缓超孔隙水压力的变化和“削峰”,降低对周围土体的影响,维护邻近结构安全.

In order to analyze the influence of shield tunneling on the surrounding soil and structure in semi closed underground space, the field data monitoring and three-dimensional finite element numerical simulation were carried out on the background of a shield section of Shanghai Rail Transit Line 7 passing through the diaphragm wall. The results show that underground diaphragm wall not only restrains the lateral displacement of soil, but also makes soft soil incline to tunnel, which increases the vertical displacement of soil. The earth pressure of the soil in semi-closed space surrounded by the diaphragm wall are approximately normal distribution in the process of shield tunneling. Excess pore water pressure of the soil increases first and then decreases. And their accumulation process is intensified and dissipation process is slowed down due to the retaining action of the diaphragm wall. The rise and fall of excess pore water pressure will significantly affect the safety of underground structures. By adjusting the grouting pressure, shield tunneling speed and laying sand piles, it can effectively slow down the change of excess pore water pressure and “cut the peak”, reduce the impact on the surrounding soil and maintain the safety of adjacent structures.