盾构穿越始发段土体加固区时土体沉降扰动分析

摘要

In the whole tunnel construction,shield construc-tion in launching section is prone to accidents. Based on the Jianghan-Jiyu Under-river Tunneling Project of Wuhan metro Line 2,program FLAC3D is adopted for numerical simulation of the soil disturbance regularity in the reinforced area of the launching section. The result shows that settlement trough in soil cross-section takes on a normal distribution during the shield construction in launching section. The soil settlement turns into diminution after soil reinforcement,showing smaller influence on the disturbance in the reinforced area than in the non-reinforced area. When shield machine passes through the interface of the reinforced and non-reinforced areas,the rate of soil settlement acceleration in the middle part is faster than it in the forepart and tail parts. When shield passes through the non-reinforced area,the soil settlement curve underground ap-pears a normal distribution: the main impacts of the process act on 18~22 meter in the transverse range,15~20 meter in the longitudinal range.%在整个盾构的掘进施工过程中,其始发段施工是事故频发的危险区段.为此,以武汉市地铁江汉路到积玉桥越江段施工为背景,选用FLAC3D软件对盾构穿过始发段全过程的土体扰动规律进行分析.数值仿真分析结果表明:在始发阶段盾构经过土体加固区时,土体横断面沉降槽呈现正态分布规律;将土体加固后,加固区的地表沉降很小,表明加固区土体受到的盾构施工扰动效应较非加固区明显减小;盾构中部通过加固区和非加固区分界面时地表沉降增加速率最大,盾构机前部和尾部通过时地表沉降增加的速率较小;盾构掘进过程中非加固区土层的沉降槽均呈现正态分布,盾构掘进主要影响盾构开挖洞口横向两侧18~22 m范围内土体,以及纵向15~20 m范围内的土体.