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盾构施工过程中,开挖面前方土拱效应与掌子面盾构机推力大小和埋深密切相关。通过室内模型试验,研究不同砂土密度和不同隧道埋深条件下,盾构开挖面前方土拱效应,分析了砂土颗粒位移变化模式和土拱发展的时变特征,并揭示了不同埋深下土拱的发展规律和对失稳破坏机制的影响;同时基于室内模型试验,采用颗粒流程序进行模拟,从细观角度进一步研究了土拱效应。结果表明:不同埋深条件下,土拱发展规律一致且与支护力大小,地表沉降密切相关;低密度时土体破坏模式呈漏斗状,高密度为条带状,且土拱范围随埋深比增大而增大;颗粒流模拟得到不同埋深条件下,颗粒接触力、孔隙率和平均土压力变化规律一致。最后得出室内试验和PFC~(2D)颗粒流模拟得到的土拱效应相似的结论。
In the process of shield construction, the soil arching effect in front of the excavation face is closely related to the thrust size and depth of the shield face machine. The soil arching effect in front of the excavation face under different sand densities and different tunnel burial depths was studied through indoor model tests. The time-varying characteristics of the displacement of sand particles and the evolution of soil arches were analyzed. The law of soil arching and its influence on the mechanism of instability failure are also discussed. At the same time, the soil arching effect is further studied from the view of meso-scale based on the indoor model test and particle flow program. The results show that under different burial depths, the law of soil arching is consistent and closely related to the size of supporting force and surface subsidence. The soil failure mode in the low density is funnel-shaped and the high density is strip-shaped, And the depth of the particles increases. The particle flow simulation results show that the particle contact force, the porosity and the average earth pressure are consistent under different depths. Finally, the conclusion of indoor test is similar to that of PFC 2D flow simulation.