复合地层土压平衡盾构压力舱渣土改良研究

为降低土压平衡盾构在复合地层中掘进时进行渣土改良的工程成本,以广州地铁21号线朱村至象岭区间为工程依托,通过对粉质黏土和砾砂不同比例组合的渣土进行颗粒分析,计算得到复合地层的粒径分布曲线,并结合室内试验和现场测试研究混合渣土的流动状态和渗透性。结果表明:当复合地层中含有粉质黏土层时,粗粒土层渣土流动状态和渗透性有较大的改善,添加少量的气泡或者膨润土泥浆,渣土状态即可满足盾构掘进的要求。粉质黏土层的含量在30%～70%之间时,渣土能够达到良好的塑性流动状态。粉质黏土层的含量超过70%时,存在结泥饼的风险。

Study on Improvement of Residual Soil in Pressure Chamber of EPB Shield in Composite Stratum

In order to reduce the engineering cost of muck improvement during the process of the excavation of Earth Pressure Balance (EPB) shield in composite stratum, based on the project of Guangzhou metro line 21 from Zhucun to Xiangling, the particle size distribution curve of composite stratum was calculated by particle analysis of different proportion combination residual soil of silty clay and gravel sand in this paper. Besides, combined with laboratory test and field test, the flow state and permeability of mixed residue soil were studied. The results show that when there is silty clay layer in the composite stratum, the flow state and permeability of the coarse-grained soil muck are greatly improved. Adding a small amount of bubbles or bentonite slurry, the muck state can meet the requirements of shield tunneling. When the content of silty clay is between 30% and 70%, the slag can reach a good plastic flow state. When the content of silty clay exceeds 70%, there is a risk of mud cake.