地铁隧道穿越砂-黏地层沉降控制技术研究

依托广州地铁区间隧道下穿条形浅基础密集民居建筑群工程,通过渣土改良试验,明确各改良参数对渣土力学性能的改良效果及其合理范围。利用FLAC3D软件模拟盾构穿越松散富水砾砂、粉质黏土和风化花岗岩复合地层的施工过程,探究可有效控制地层沉降变形的盾构施工参数范围。研究表明:基于室内渣土改良试验用发泡剂浓度为3%的泡沫剂进行渣土改良,控制渣土含水率在16.95%、20.95%左右,泡沫剂掺入比分别为21%~46%、71%~92%,可将渣土塌落度、渗透性等力学性能改良至理想状态;根据盾构实况,应调整土仓压力大于原应力平衡体系静水土仓压力;通过增大注浆压力,最大化密实地层空隙与盾尾脱空间隔,提高加固层弹性模量,控制地层不均匀沉降;对比分析试验段、下穿段和危害建筑物的沉降监测数据,施工过程中采取渣土改良措施与设定优化的盾构参数,可将地层与危害建筑物的变形控制在规定的安全范围内。为类似盾构隧道提供技术指导。

Study on Settlement Control Technology for Subway Tunnels through Sand-Clay Strata

Relying on Guangzhou Metro Interval Tunnel underpassing the strip shallow foundation dense residential building group project, the effect and reasonable range of the modified parameters on the mechanical properties of muck were clarified based on muck improvement tests. FLAC3D software was used to simulate the construction process of shield tunneling through composite stratum of loose water-rich gravel sand, silty clay and weathered granite. The construction parameter range of shield tunneling which can effectively control the formation subsidence deformation is explored. Study shows that based on the indoor slag improvement test, a foaming agent with a foaming agent concentration of 3% is used to improve the slag, and the moisture content of slag is controlled at about 16.95% and 20.95%, and the foaming agent blending ratio is 21%~46% and 71%~92% can improve the slump, permeability and other mechanical properties of the muck to an ideal state. According to the actual situation of the shield, the pressure of the soil bin should be adjusted to be greater than the pressure of the static water soil bin of the original stress balance system. By increasing the grouting pressure, the gap between dense formation and the gap between the shield tail is minimized, the elastic modulus of the reinforcement layer is increased, and the uneven settlement of the formation is controlled. Comparing and analyzing the settlement monitoring data of the test section, the underpass section and the hazardous building, it is known that the muck improvement measures and optimized shield parameters set during the construction process can control the deformation of stratum and hazardous building to the specified level within a safe range. The study can provide technical guidance for similar shield tunnels.