砂卵石地层盾构施工对地层扰动与地表沉降的影响分析

ANALYSIS ON INFLUENCING OF THE CONSTRUCTION OF SHIELD TUNNEL ON STRATUM DISTURBANCE AND GROUND SETTLEMENT IN SANDY PEBBLE STRATUM

以成都高漂石含量砂卵石地层为研究对象,采用PFC2D模拟了双线隧道盾构掘进时对砂卵石地层的扰动规律,并通过Midas有限元模拟分析了双线隧道盾构掘进时的地表沉降规律。结果表明砂卵石地层在掘进过程中将形成一个倒三角的松动区,并引起掌子面前方土体向此区域移动,最终形成楔形移动面;同一里程处隧道引起的地表沉降随着盾构推进呈增大趋势,根据监测数据显示,地表沉降规律与模拟结果基本一致;双线盾构施工时,左右两侧的地表沉降相互影响,最大沉降位置将随着开挖方向发生偏移,并呈中心轴线沉降量最大,两侧地表沉降亦呈现出基本对称分布的规律。

Taking the sandy pebble stratum with high boulder content in Chengdu as the research object,this paper used PFC2D to simulate the disturbance law of double track tunnel shield tunneling on sandy pebble stratum,and Midas finite element to simulate and analyze the surface settlement law of double track tunnel shield tunneling.The results showed that:(1)an inverted triangle loose area will be formed in the sandy pebble stratum during excavation,which will cause the soil in front of the tunnel moving to this area,and finally form a wedge-shaped moving surface;(2)the surface settlement caused by the tunnel at the same mileage increases with the shield tunneling.According to the monitoring data,the surface settlement law is basically consistent with the simulation results;(3)during double-line shield construction,the maximum settlement position will deviate along the excavation direction.The maximum settlement amount will be at the central axis and the surface settlement on both sides will show a basic symmetrical distribution law.