砂砾地层矩形截面管廊顶管施工超挖空洞消除方法

An Eliminating Method of Over-excavated Holes in Pipe-jacking Construction of Utility Tunnel with Rectangular Cross-section in Gravel Stratum

包头市某矩形截面综合管廊需下穿市内某主干道,下穿段管廊位于复杂砂砾地层中,采用顶管法施工初期地下出现较大超挖空洞。在实地调查、分析施工参数基础上,采用原因关联分析方法找出土压表被砂石堵塞、减摩泥浆在土体中流失以及改良泥浆配合比不适用这三个主因。通过比选,采取为顶管设备增配全断面土压监测系统、采用注泥设备向管节外部注入浓泥稠浆形成不透水"泥壳"、调整膨润土泥浆配合比等应对措施,成功在后续顶进施工过程中消除了地下超挖空洞,现场顶管上方土体沉降观测结果均满足限定要求。

A rectangular cross-section utility tunnel which cross a main road in Baotou is located in a complex sand gravel stratum, and large underground over-excavated holes appear at the initial construction stage by pipe-jacking construction. Based on field investigation and analysis of construction parameters, three main reasons including the clogging of pressure gauge by sand gravel, the loss of anti-friction mud in soil and the inapplicability of modified mud mix ratio are found by means of cause correlation analysis. By comparison, corresponding measures are taken, such as adding whole section earth pressure monitoring system to the pipe jacking equipment, injecting thick mud into the external pipe sockets by mud injection equipment to form a impermeable "mud shell", and adjusting the mix ratio of bentonite mud. The underground over-excavated holes have been eliminated in the subsequent pipe-jacking construction process successfully, and the field observation results of soil settlement have met the requirements.