地表超载对软、硬地层中既有盾构隧道影响的试验研究

Experimental study on influences of surface surcharge on existing shield tunnels buried in soft and hard soils

为了探明地表超载对软、硬地层中既有盾构隧道的影响,通过隧道与地层相互作用的模型试验,对地表超载作用下隧道变形、土压力及土体沉降进行了量测。试验结果分析表明,相同的地表超载作用下,软土地层中的隧道横椭圆变形要大于硬土地层中的隧道横椭圆变形。当隧道穿越土层的土体压缩模量较小时,地表超载作用下隧道上覆土层表现为被动土拱土压力;当隧道穿越土层的土体压缩模量较大时则为主动土拱土压力。隧道竖向收敛变形与其穿越土层竖向压缩量之间的关系分析表明,隧道横断面变形刚度与穿越土层的土体压缩模量共同决定隧道上覆土层的沉降状态,从而决定了地表超载对既有盾构隧道的影响。研究成果定性地揭示了软土地区既有盾构隧道在地表超载作用下极易发生变形超限的机理。

To explore the influences of surface surcharge on the existing shield tunnels buried in soft and hard soil strata,the scaled model tests on the interaction between shield tunnels and strata are carried out,and the tunnel deformation,earth pressure and soil settlement under surface surcharge are measured.Analysis of model test results shows that under the same surface surcharge,larger deformation is induced for the tunnel buried in soft soils than in hard soils.As the compression modulus of the soil strata is small,the overlaying soils over the tunnel exhibit passive earth arch pressure under surface surcharge.Under the large compression modulus of the soil strata,the overlaying soils over the tunnel show active earth arch pressure.The relation between the vertical convergence deformation of the tunnel and the vertical compression of the soil strata indicates that both the stiffness of cross section of shield tunnel and the compression modulus of soil strata determine the settlement state of the overlaying soils over the tunnel,and thus decide the influences of surface surcharge on the existing shield tunnels.The research results qualitatively reveal the reason of the mechanism why the oversized deformation is easily induced for the existing shield tunnels under surface surcharge.