盾构隧道穿越粉细砂层时的地表沉降分析

当盾构拱顶遇到粉细砂层,地表沉降累积值和速率均易超标。通过绘制单线盾构隧道地表沉降空间分布图,发现沉降大的区域与粉细砂层有明显的相关性。原因是粉细砂的粘聚力较小,自稳性差,容易受扰动坍塌,引起较大超挖。采用有限元软件Plaxis进行数值模拟。结果表明,相同盾构掘进参数下,含粉细砂区域的地层地表沉降明显偏大。

Analysis of Surface Subsidence with TBM Boreing through Fine Sand Stratum

Boring through the fine sand stratum with TBM (tunnel boring machine) will cause great and fast surface subsidence,which may exceed the limits given by designers,By drawing the spatial distribution of surface subsidence for single shield tunnel,the obvious correlation between large area of surface subsidence and the fine sand stratum is detected,because the fine sand is vulnerable to collapse due to its weak cohesion,which results in unnecessary over-excavation.Numerical simulation with finite element software Plaxis also indicates that fine sand stratum is more susceptible to surface subsidence than clay layer when the shield driving parameters are the same.