板岩地层盾构掘进对地层扰动的现场试验研究

长沙地区板岩的特点是遇水易软化、崩解,目前未见对该地层盾构掘进引起地层扰动的相关研究。以长沙地铁2号线西延线一期工程为依托进行了现场试验,监测内容包括:地表沉降、土体水平位移、土压力和孔隙水压力,同时记录掘进参数。通过分析得知:(1)板岩地层盾构总推力、扭矩和土仓压力是同步变化的,埋深不变时土仓压力随着隧道断面内微风化板岩所占比例的增加而增大;(2)地表沉降、土体水平位移、土压力和孔隙水压力随着切口到断面距离的变化规律基本一致;(3)各测点横向地层位移最大值约为轴向的1.1~2.6倍;(4)根据土体应力随切口到断面距离变化规律,将应力扰动分为缓慢减小段、波动段、缓慢变化段和恢复段4个阶段。

Field Test Research of Ground Disturbance by Shield Tunnelling in Slate Strata

Slate is easy to be disintegrated and be softened after absorbing water in Changsha area. No relevant researches are found about ground disturbance caused by shield tunnelling in slate strata. Field test of disturbance is done in the engineering background of first phase of west extension line of Changsha metro line 2. The monitoring items includ ground surface settlement, soil displacement, earth pressure and pore water pressure. Shield tunnelling parameters are recorded simultaneously. Monitoring data analysis indicates that: (1) total thrust, torque and chamber pressure are synchronized changes, and chamber pressure increases with ratio of light weathered slate in excavation face when depth unchanged; (2) the variation rules of surface settlement, soil displacement and soil stress with distance between shield cutter and testing section are basically consistent; (3) the maximum transverse soil displacement of each measuring point is about 1.1~2.6 times of axial value; (4) ground stress disturbance can be divided into 4 stages, slowly decreases stage, fluctuations stage, slowly changing stage and recovery stage, according to the rules of soil stress.