土压平衡盾构掘进对散粒体地层扰动和开挖面破坏特性研究

 采用自主研制的? 800 mm土压平衡盾构掘进试验系统，对砂卵石与砂土地层开展室内缩尺掘进试验研究，以分析土压平衡盾构掘进对地层的扰动特征；同时，针对室内缩尺掘进试验，开展离散元数值模拟以分析盾构掘进开挖面的变形与破坏形态。研究表明：砂土地层地表沉降曲面自上而下呈现逐渐收缩的“圆形漏斗”状，砂卵石地层地表沉降曲面自上而下呈现逐渐收缩的“V型河谷”状；砂卵石地层地表横断面沉降槽宽度系数相比砂土地层要小；2种地层地中沉降槽宽度参数都随地中深度比的增加而呈线性增大，相同深度比条件下砂卵石地层地中沉降槽宽度参数要小于砂土地层；砂土地层沉降时间效应曲线较为渐进和连续，而砂卵石地层则呈现突变性；2种地层开挖面破坏形态均为烟囱状，但砂卵石地层的开挖影响范围无论在横向还是纵向上都要小于砂土地层。

Study on the disturbance and excavation face failure feature of granular mixtures stratum due to EPB shield tunneling

The scaled driving test was carried out to study the disturbance of EPB shield tunneling to the sandy cobble stratum and sandy stratum using ? 800 mm EPB shield tunneling system. The deformation and failure mode of the excavation face were analyzed using DEM. The profile of three-dimensional trough of surface settlement in sandy stratum has the shape of “round funnel” with a gradual contraction from top to bottom while that in sandy cobble stratum looks like a “Valley”. The width coefficient of surface cross-section trough of sandy cobble stratum is smaller than that of sandy stratum. The subsurface trough width parameter of both stratum increased linearly with the depth ratio. When the depth ratios are the same，the subsurface trough width parameter of sandy stratum is larger than that of sandy cobble stratum. The time-effect curve of ground settlement of sandy stratum shows gradual and continuous characteristics while that of the sandy cobble stratum shows settlement jumps. The deformation and failure modes of the excavation face in both stratum show a chimney shape，but the disturbance scope in sandy cobble stratum due to excavation is smaller than that in sandy stratum.