隧洞拱冠砂土位移与破坏的离心模型试验研究

A Study of the M ovem ent and Failure Characteristicsof Sand M ass Above the Crow n of a Tunnel

通过离心模型试验，对隧洞拱冠以上地层位移与隧洞内支护压力的关系及临界支护压力进行了研究。结果表明：在砂土中开挖隧洞，由于砂土抗剪强度的发挥，隧洞拱冠以上砂土在远小于原位上覆土压力的支护压力下仅发生一定的位移而不致塌落；因此，若允许地表面发生少许沉降，隧洞内支护压力可以比原位上覆土压力有较大程度的降低。

A series of centrifugal tunnel tests in sandy soil ground w ere conducted to investigate thebehavior of sand above the crow n of a tunnel during excavation. The centrifugal test results show that thecritical (m inim um ) support pressure needed to avoid collapse of sand m ass above the crow n of a tunnel ism uch sm aller than the overburden pressure. If a certain value of displacem ent is allow ed, the supportpressure m ay have a significant decrease during shield tunnelling process.