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在泥水平衡盾构施工过程中,如何确保施工安全并减少对周边环境的影响受到国内外学者的广泛关注,地层土体稳定性问题显得尤为重要,但对于砂质地层开挖面稳定性的失稳机制及其稳定性分析尚处于经验阶段。利用大尺寸模型试验,研究了不同水头高度(无水、0.9 m和1.1 m)下两种地层中开挖面主动破坏的发展模式和受力情况。试验中分析了不同水头高度对开挖面主动破坏的影响,研究结果表明:砂质土层中盾构隧道开挖面失稳时,存在土拱效应,使得地表对开挖面主动破坏的响应存在滞后效应;根据水头高度不同,可将砂质地层中开挖面主动破坏发展模式划分为无水模式、低水头模式和高水头模式;在形成泥膜和提供支护力的过程中,会在砂质土层中产生超孔隙水压力,在确定支护力时,应在静止土压力和静水压力的基础上,考虑超孔隙水压力的影响。研究结果对确定开挖面极限支护压力有重要的指导意义。
How to ensure the construction safety and reduce the impact on the surrounding environment during the construction of the slurry balance shield has drawn wide attention from domestic and foreign scholars. The stability of the formation soil is particularly important. However, for the stability of the excavation face of the sandy formation, The stability mechanism and its stability analysis are still in the empirical stage. The large-scale model test was used to study the development modes and forces of the active failure of the excavation face in two kinds of stratum with different water head height (no water, 0.9 m and 1.1 m). The effect of different head height on the active failure of the excavation face is analyzed in the experiment. The results show that the soil arching exists in the shield tunnel when the excavation face is unstable in the sandy soil, and the response of the earth’s surface to the active failure of the excavation face There is a hysteresis effect; according to the different head height, the active failure mode of excavation face in sandy strata can be divided into waterless mode, low head mode and high water head mode. During the formation of mud membrane and supporting force, The excess pore water pressure is generated in the sandy soil layer. When determining the supporting force, the influence of the excess pore water pressure should be considered on the basis of the static earth pressure and the hydrostatic pressure. The research results have important guiding significance for determining the limit supporting pressure of excavation face.