软弱地层盾构隧道侧穿房屋基础沉降特性分析

以广州轨道交通21号线金坑站—镇龙南站区间土压平衡盾构下穿均和村房屋群为工程依托,采用数值模拟方法研究盾构隧道侧穿房屋群基础沉降特性,对比分析不同隧道开挖顺序下房屋基础沉降响应规律,并结合现场实测数据进行对比分析,揭示软弱地层盾构隧道侧穿房屋群施工扰动特性。研究结果表明:(1)在软弱地层双线隧道侧穿既有建筑物时,优先施作受荷载作用显著侧隧道,可有效降低既有建筑物变形;(2)在软弱地层盾构隧道掘进过程中,地表既有建筑物产生的主要沉降位于隧道穿越既有建筑物前3倍洞径至穿越建筑物后6倍洞径范围内,在此区段内可加强监测力度,根据实际需求采取降低掘进速度或适当加大注浆量的控制措施来控制既有建筑物变形;(3)受软土地层特性和施工同步注浆浆液固化的影响,在盾构穿越监测点10 m左右监测点沉降达到最大,随着浆液强度的增大,存在沉降回弹现象。

Analysis on Settlement Characteristics of Building Foundation Side-passed by Shield Tunnel in Weak Stratum

Based on the earth pressure balance shield of Jinkeng Station and Zhenlongnan Station of Guangzhou Rail Transit Line 21 passing under the Junhe Village houses, the numerical simulation method is used to study the building foundation settlement characteristics side-passed by shield tunnel. The response law of building foundation settlement in different tunnel excavation sequences is analyzed based on field measured data, and characteristics of the construction disturbance to the houses side-passed by the shield tunnels in weak stratum are revealed. The results show that:(1) When two-lane tunnels in the weak stratum side-passing the existing buildings, the construction of the tunnel with the significant load is prioritized, which can effectively reduce the deformation of the existing buildings;(2) During the construction process, the main settlement of the existing buildings is located within the range from 3 times the diameter of the tunnel before the existing building to 6 times the diameter of the tunnel after passing the building. Therefore, the monitoring intensity should be strengthened in this section. According to actual needs, control measures should be taken to control the deformation of the existing building by reducing the speed of excavation or increasing properly the amount of grouting;(3) Influenced by the characteristics of weak stratum and the solidification of grouting slurry, the settlement reaches the maximum at about 10 m away from the monitoring point of the shield, and with the increase of slurry strength, sedimentation is likely to rebound.