软黏土中盾构掘进地层变形与掘进参数关系

宁波地铁某区间单线隧道穿越地层主要为淤泥质黏土层,上覆地层主要为砂质粉土和淤泥质土.针对2类典型的上覆地层中土压平衡盾构施工,获取了相应的地表沉降监测数据,研究地表沉降与盾构施工过程的相互关系.采用经典高斯经验公式对盾构掘进引起的地表横向沉降曲线和纵向沉降发展曲线进行拟合,得到各监测断面沉降槽宽度ix及沉降槽宽度系数K.采用平移累积高斯沉降曲线对纵向沉降发展曲线进行拟合,获得盾构掘进引起的沿线地层损失率.研究盾构掘进参数取值对地层损失率的影响.结果表明,盾构推力、开挖面支护压力以及盾尾注浆率对地层损失率的影响显著.给出类似地层中各项盾构掘进参数的参考范围.

Tunnel boring machine tunneling-induced ground settlements in soft clay and influence of excavation parameters

Measurements of ground settlements induced by the construction of a single tunnel mainly in soft clay of Ningbo Metro Line were presented. The soils above tunnel were mainly sandy silt and mucky clay, and the tunnel was constructed using earth pressure balanced (EPB) tunnel boring machine. Ground settlements due to shield tunneling were back-analyzed using the classical Gaussian empirical predictions, both in the transverse and longitudinal directions. Thus the transverse settlement trough parameters ix and K were obtained. Translated Gaussian cumulative curves were proposed to better match the evolution of settlements during tunnel advancement. The ground volume loss along the alignment was obtained, and the influence of excavation parameters on the volume loss was investigated. Results indicate that the total thrust force of the shield, normalized face-support pressure and backfilling grouting ratio can markedly influence the ground volume loss. Suggested ranges of different excavation parameters were presented．