大断面矩形顶管近穿既有地铁隧道数值模拟分析

Numerical simulation analysis of large section rectangular pipe jacking closely passing through existing subway tunnel

为探究大断面矩形顶管近距离上穿既有地铁隧道时地表及隧道结构变形影响规律,利用PLAXIS3D有限元软件进行了顶管施工全过程模拟,同时分析了掌子面推进力、地层损失、顶管内配重等施工参数影响。结果表明:在顶管施工过程中,地表经历先隆起后沉降过程,隆起最大值达1.80 mm,沉降最大值始终位于顶管掘进中心线上方,最大沉降量达到11.40mm。既有隧道向接收井一侧隆起变形,左、右线隆起最大值介于2.76~3.97 mm之间,且隧道所受影响主要在顶管通道的投影区域。掌子面推进力增加使得前方地表土体隆起增大,并引起更大的隧道位移;地层损失率从0%提升到0.2%,顶管后方土体沉降从8.58 mm增加至11.10 mm,而隧道的最大位移量变化不超过1mm;增大顶管内配重可使得地表和既有隧道沉降均加大。实际施工过程中应适当减小掌子面推进力和地层损失,顶管内适当配重,以减小前方过大地表隆起和顶管推进后过大工后沉降。

In order to explore the influence law of construction parameters on the surface and subway tunnel deformation during the pipe jacking closely passing through existing subway tunnel,PLAXIS 3D finite element software was used to simulate the construction process.And the influence of pipe jacking on surface and existing subway tunnel deformation was analyzed by changing the construction parameters such as the thrust of the tunnel face,the ground loss,and the counterweight conditions in the pipe jacking.The analysis results show that during the pipe jacking construction process,the surface experienced a process of uplifting and then subsiding,the maximum uplift is 1.8 mm,the maximum settlement is always above the center line of pipe jacking excavation,and the maximum settlement is 11.4 mm.The existing tunnel bulges and deforms towards one side of the receiving shaft.The existing tunnel uplifted and deformed to the side of the receiving shaft,the maximum bulge of the left and right tunnel is between 2.76 mm and 3.97 mm,and the tunnel is mainly affected in the projection area of the pipe jacking channel.The increase of the propulsive force of the tunnel face increases the uplift of the front surface soil and causes greater tunnel displacement.The formation loss rate increased from 0%to 0.2%,the soil settlement behind pipe jacking increased from 8.58 mm to 11.10 mm,and the change of the maximum displacement of the tunnel did not exceed 1 mm.The increase in the pressure in the jacking pipe will cause the surface and the existing tunnel to settle.In the actual construction process,the thrust of the tunnel face and the loss of stratum shall be appropriately reduced to reduce the excessive ground uplift in front and the excessive post construction settlement after pipe jacking.