地表均布超载作用下盾构隧道上覆土层竖向土压力转移分析

Analysis for vertical earth pressure transference on overlaying soils of shield tunnel under uniform surface surcharge

通过对地表均布超载的模型试验实测既有盾构隧道上覆土层竖向土压力、土体沉降进行分析,结果表明:地表均布超载作用下,与隧道顶部的垂直距离越近,隧道上覆土层中的竖向土压力分布不均匀程度越大,同时土体沉降的不均匀程度也越大。隧道上覆土层出现不均匀沉降时,土体单元之间发生竖向相对位移而产生竖向剪力,隧道上覆土中表现出竖向土压力转移现象,从而使隧道上覆土层中的竖向土压力分布不均匀。隧道上覆土层中土体单元之间的竖向剪力大小与单元之间的竖向相对位移及土体力学性能有关,因此,地表超载作用下隧道上覆土沉降的不均匀程度及上覆土的力学性能对隧道上覆土层的竖向土压力分布不均匀程度有影响,进而对隧道变形产生影响。

Scaled model test for the influence on an existing shield tunnel induced by surface surcharge is carried out,and vertical earth pressure and soil settlement for the stratum above the shield tunnel are analyzed.Results show that under uniform surface surcharge,the less of the vertical distance from the top of the tunnel,the more extent for the nonuniform vertical earth pressure in the stratum above the shield tunnel,and the more extent for the nonuniform soil settlement of overlaying soils of the shield tunnel.The overlaying soils show vertical earth pressure transference for vertical shearing force among soil elements,which is induced by vertical relative movement among soil elements as the stratum above the shield tunnel has nonuniform soil settlement,so the vertical earth pressure in the stratum above the shield tunnel is nonuniform.As vertical shearing force among soil elements for overlaying soils is related to vertical relative movement among soil elements and soil mechanical property,the extent of nonuniform vertical earth pressure in the stratum above the shield tunnel is affected by the extent of nonuniform soil settlement and soil mechanical property of overlaying soils when the tunnel suffers from surface surcharge,so the tunnel deformation is influenced.