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采用自主研制的φ800 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形河谷”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。
The self-developed φ800 mm earth pressure balance shield tunneling test system was used to carry out indoor scale excavation test on sandy pebbles and sand stratum to analyze the disturbance characteristics of earth pressure balance shield tunneling to the formation. At the same time, Tunneling test and carry out discrete element numerical simulation to analyze the deformation and failure modes of shield tunneling face. The results show that the surface subsidence curved surface of sand soil shows a “circular funnel” shape which shrinks from top to bottom. The surface subsidence curved surface of sand-pebble formation presents a “V-shaped valley” shrinking from top to bottom; The width coefficient of surface sedimentation tank is smaller than that of sandy soil; the width parameters of the middle sedimentation tank in both kinds of ground show a linear increase with the increase of medium-depth ratio, and the width parameters of middle-settling tank in sand-gravel formation under the same depth ratio The sedimentary time-effect curve of sand stratum is more gradual and continuous, while the gravel stratum shows catastrophe. Both of the two kinds of stratum excavation surface have the shape of chimney. However, Horizontal or vertical should be less than the sand formation.