摘要:
软土深部地层进行盾构隧道开挖，所引起的土拱时效与隧道埋深及软土蠕变特性有着直接的联系。本文通过离心机试验，模拟软土深埋盾构隧道在开挖以及后期长时间蠕变阶段的全过程，获得了开挖面的土压力值时效变化规律。本试验设置多组独立的模型试验，模拟4D 埋深与6D 埋深两种覆土厚度的工况。根据离心机性能指标以及模型尺寸限制条件，重力加速度选为50g、70g、90g，以对应实际工况中的中埋、深埋、超深埋三种情况，每组试验中均采取主动卸荷、被动加荷两种开挖模式，通过不同埋深、不同开挖方式对土拱效应影响的对比，共进行12 组对比试验，分析盾构开挖的掌子面压力变化、土拱产生以及衰减规律。由试验得到，在软土深部地层（≥4D）开挖，采取卸荷开挖模式，则盾构机以及管片在开挖 2 年后所承受的长期土压力比静止土压力减小约 20%；采取加荷土压力开挖模式，在后期长期蠕变过程中，管片所承受的被动土压力逐步减小，盾构管片长期承受的土压力维持值比静止土压力增加约 20%，为软土深部地层盾构开挖提供了重要的时效性参考数据。
Abstract:
The soil arching caused by shield tunnel excavation in deep soft soil layers is directly related to the tunnel depth and creep characteristics of soft soil. This article simulates the entire process of excavation and long-term creep of a deep buried shield tunnel in soft soil through centrifuge experiments, and obtains the temporal variation law of soil pressure values on the excavation surface. This experiment sets up multiple independent model tests to simulate two types of soil cover thickness conditions: 4D burial depth and 6D burial depth. Based on the performance indicators of the centrifuge and the size limitations of the model, the gravity acceleration was selected as 50g, 70g, and 90g to correspond to the three situations of medium burial, deep burial, and ultra deep burial in actual working conditions. In each experiment, two excavation modes, active unloading and passive loading, were adopted. By comparing the effects of different burial depths and excavation methods on soil arch effect, a total of 12 comparative experiments were conducted to analyze the changes in face pressure, soil arch generation, and attenuation laws of shield tunneling. According to the experiment, when excavating in deep soft soil layers (≥ 4D) using unloading excavation mode, the long-term soil pressure borne by the shield machine and pipe segments after 2 years of excavation is reduced by about 20% compared to the static soil pressure; Adopting the excavation mode of adding soil pressure, during the long-term creep process in the later stage, the passive soil pressure borne by the tunnel segments gradually decreases, and the long-term soil pressure maintained by the shield tunnel segments increases by about 20% compared to the static soil pressure, which provides important time sensitive reference data for shield tunneling excavation in deep soft soil formations.
百度学术
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