复杂地层浅埋大断面矩形顶管上跨既有隧道加固效果分析

Analysis of the Reinforcement Effect of a Shallow Buried Large Section Rectangular Pipe Jacking Tunnel over an Existing Tunnel in Complex Strata

城市地下交通发展,临近地下结构施工作业频繁,有效地隔离保护措施对地下结构安全十分重要。以福州滨海快线某地铁枢纽车站换乘通道顶管工程为例,采用有限元软件PLAXIS建立了复杂地下空间下浅埋大断面顶管上跨既有线掘进数值模型,模型中考虑了沿海软黏土小应变硬化(HSS)特性及其参数取值方法,分析了管幕隔离-MJS地层加固联合作用下浅埋大断面顶管施工对周围环境的影响。计算结果表明:①管幕加固可有效减弱区域范围内地表沉降,“口”字形全封闭管幕对于地表沉降的控制效果可以达到87%,仅上下排管幕相较无管幕情况减小34.9%;②管幕+MJS加固时拱底隆起最大值约2.9 mm,仅MJS加固时拱底隆起最大值3.2 mm,无任何加固的情况下拱底隆起最大值3.9 mm;③既有地铁隧道,在管幕+MJS加固下最终控制最大上浮量2.36 mm。研究结果可对沿海淤泥黏性土地层中盾构、顶管施工的地表沉降控制及邻近地下结构隔离防护措施提供一定参考。

With the development of urban underground transportation and frequent construction in the vicinity of underground structures,effective isolation and protection measures are important for the safety of underground structures.Taking the pipe jacking project at an underground hub station of the Fuzhou Binhai Express Line as an example,the finite element software PLAXIS was used to establish a numerical model of shallow buried large section pipe jacking across existing lines in complex underground spaces.The influence of the construction of shallow buried large section pipe jacking on the surrounding environment under the combined effect of pipe isolation and MJS ground reinforcement was analyzed.The calculation results show that:①The pipe curtain reinforcement can effectively reduce the surface settlement in the area,and the control effect of"mouth"shaped fully enclosed pipe curtain on surface settlement can reach 87%,only the upper and lower rows of pipe curtain can reduce 34.9%compared with the case without pipe curtain;②The maximum value of arch bottom uplift is about 2.9 mm when pipe curtain+MJS reinforcement,when only MJS reinforcement is used,the maximum arch bottom uplift is 3.2 mm,and without any reinforcement,the maximum arch bottom uplift is 3.9 mm;③The existing subway tunnel,with the reinforcement of the pipe curtain and MJS,ultimately controls a maximum uplift of 2.36 mm.The results of the study can be used as a reference for surface settlement control of shield and pipe jacking construction and isolation and protection measures for adjacent underground structures in coastal silty clayey ground.