既有建筑箱基荷载对邻近浅埋隧道开挖效应影响的模型试验研究

Modeling Experimental Study on the Influence of Pre-Existing Building Box Foundation Load on the Effect of Adjacent Shallow Buried Tunnel Excavation

建立由试验台架和加载装置、地层—箱基荷载—隧道开挖—隧道支护模型,以及箱基荷载、地层应力、隧道拱顶沉降和支护应变的量测装置所构成的平面(垂直于隧道开挖方向的)应变模型试验系统;通过模型试验,研究不同水平、竖向位置处既有建筑箱基荷载对邻近浅埋隧道开挖效应的影响,分析地层应力重分布、隧道拱顶沉降和隧道支护弯矩等的变化特征。试验结果表明:箱基荷载会明显地改变邻近隧道开挖引起的地层应力重分、隧道的拱顶沉降和支护弯矩;箱基荷载对其正下方地层应力重分布的影响明显大于对其他部位地层应力重分布的影响;地层应力随着箱基埋深的增加而增大;隧道拱顶沉降随着箱基荷载位置与隧道中心线水平距离的减小而增大、随着箱基埋深的增加而增大且增加速率越来越大;箱基荷载对隧道支护弯矩的影响随着箱基荷载位置与隧道拱顶水平距离、竖向距离的增加而减小。

An experimental model system was set up,which in nature plane strain perpendicular to thetunnel drive encompassed a ground model,a box foundation load model,a shallow tunnel excavation model and an associated tunnel support model,together with devices and instruments for measuring box foundation load,stratum stress,tunnel crown settlement and support strain.Experiments were conducted to study the influence of existing box foundation load of various horizontal and vertical positions on the stratum stress redistribution,tunnel crown settlement,and the bending moment of tunnel support for a nearby shallow buried tunnel excavation of fixed ground loss.The experimental results showed that the pre-existing box foundation load might obviously change the stratum stress redistribution,the tunnel crown settlement and the bending moment of the tunnel support induced by adjacent tunnel excavation.The box foundation load exerted more influence on the stress redistribution of the soil directly underneath than other locations.The stratum stress increased with the buried depth of box foundation.The settlement of the tunnel crown increased with the decrease of the horizontal distance between the position of box foundation load and tunnel central line,meanwhile,it also increased with the buried depth of box foundation and its increasing rate became larger and larger.The influence of box foundation load on the bending moment of tunnel support decreased with the increase of the horizontal and vertical distances between the position of box foundation load and tunnel crown.