软、硬地层中局部堆载对隧道横向变形影响的试验研究

Experimental Study of the Influence of Surface Surcharge on Tunnel Lateral Deformation in Soft and Hard Soil

摘要:

通过缩尺模型试验研究了局部堆载位置对软、硬地层中隧道横向变形的影响机理，考虑不同堆载位置和隧道穿越土层性质，测量了分级加?卸载过程中隧道管片的椭圆度、接头张开量和附加土压力的变化情况。试验结果表明，当荷载大小相同时，随堆载偏心距增加，隧道椭圆度先迅速减小然后趋于平缓，堆载导致软土层隧道的椭圆度大于硬土层隧道，并且增加偏心距后软土层隧道椭圆度的减小更明显。增加堆载偏心距可以有效减小隧道接头的张开量，正上方堆载时变形主要发生在隧道左右肩部与顶部接头，偏心堆载时变形主要发生在荷载对侧的肩部与顶部接头。堆载作用下砂土层隧道土压力分布较均匀，而软土层隧道土压力主要集中于水平方向，随着偏心距增加，土压力逐渐减小且主要集中点向荷载对侧的斜截面转移。最后，采用有限元模拟进行了主要影响因素的参数分析，对运营隧道上方堆载与保护提出了相关建议。

Abstract:

The influence mechanism of surface surcharge position on tunnel lateral deformation in soft and hard soil is studied by using the scale model test. Considering different surcharge position and tunnel traversing soil layer properties， the changes of ellipticity， the joint opening， and the additional earth pressure of tunnel segment during the graded loading-unloading process are measured. The test results show that when the load is the same， the tunnel ellipticity decreases rapidly first and then tends to smoothen with the increase of eccentricity of surcharge， the ellipticity of the tunnel in soft soil layer is larger than that of the tunnel in hard soil layer due to loading， and the decrease of tunnel ellipticity in soft soil layer is more obvious with the increase of eccentricity. Increasing the eccentricity of surcharge can effectively reduce the opening of the tunnel joint. The deformation mainly occurs in the left and right shoulder and the top joint of the tunnel when the load is directly above， and mainly in the shoulder and the top joint on the opposite side of the load during eccentric loading. Under the action of surcharge， the earth pressure of the tunnel in the sandy soil layer is uniformly distributed， while that in the soft soil layer is mainly concentrated in the horizontal direction. With the increase of eccentricity， the earth pressure decreases gradually and the main concentrated point shifts to the oblique section of the opposite side of the load. Finally， based on the results of finite element parameter analysis， the protection suggestions on the surface surcharge in the operating tunnel are proposed.