不同埋深砂土盾构隧道掘进开挖面前方土拱效应研究

Arching effect of soil ahead of working face in shield tunnel in sand with various depths

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。

The soil arching effect is closely related to the supporting force and depths during tunneling construction. The soil arching effect was studied experimentally considering various depths of embedded tunnel and densities of the sand layer. The displacement of sand particles and development of soil arching near the face of excavation were analyzed. The development of soil arching and the its failure under various depths were revealed. Comparing with the laboratory tests, the two-dimensional particle flow code（PFC^（2D）） was employed to simulate the soil arching effect. The results show that the development of soil arching under different depths are the same, closely related to the supporting force and the ground settlement. The failure of soil shows funnel shape at low density, and strip shape at high density. The range of soil arching increases with the increase of depths. The change of particle contact force, porosity and average soil pressure are the same via PFC^（2D） simulation for various depths. Finally, the conclusion is drawn that the soil arching effect obtained from the laboratory tests is similar to that of PFC^（2D） simulation.