软土地区盾构掘进引起的深层位移场分布规律

DISTRIBUTION OF DEEP DISPLACEMENT FIELD DURING SHIELD TUNNELING IN SOFT-SOIL AREAS

在城市环境中,如何预测和控制盾构掘进引起的地层移动以保证地下既有构筑物的安全,是设计和施工亟待解决的技术问题。以上海某盾构隧道施工段为工程背景,应用现场监测和数值模拟相结合的方法,研究盾构掘进施工引起周围地层位移场的分布规律。研究结果表明:盾构掘进对周围地层位移场的影响主要分为接近、穿越和远离测孔3个阶段。在盾构掘进接近和穿越阶段,隧道侧向土体以隆起、沿盾构掘进方向向前和向隧道外侧的位移为主;在远离阶段,侧向土体则发生沉降、向前和向隧道内的三维运动趋势。由于该工程隧道埋深大,隧道中心上方土体主要发生沉降和向前的位移趋势。根据数值计算所得隧道上方不同深度土层的横向沉降槽曲线,建立用于预测隧道上方深层土体沉降的修正Peck公式,计算结果与数值结果吻合较好。

The main issue considered both in design and construction in urban environments is constrolling ground movement to keep the safety of existing buildings. Based on a shield tunnel construction in Shanghai, the ground displacement distribution around tunnel is studied by field measurement and numerical analysis. It is shown that the influence of shield excavation on soils around tunnel can be divided into three stages, including shield approaching, crossing and leaving the measuring holes. While the shield approaches and crosses the measuring holes, the ground movements of lateral soil behave heaving, moving along the shield tunneling direction and outward the tunnel. Settlement, moving along the shield tunneling direction and inside the tunnel are main deformation characteristics when the shield leaves the measuring holes. Settlement and forward movement the soils above tunnel because of the large buried depth. According to the calculated layered settlement above tunnel, modified Peck formula used to predict the settlement of deep soils is established; and the results are compared with those of simulation.