近接开挖与列车振动对既有铁路隧道的沉降影响研究

选取不同近接距离基坑开挖来研究隧道的沉降变化规律,利用激振荷载经验公式来模拟高速列车的轮-轨激振力,并运用有限差分动力分析方法分析不同距离基坑开挖作用下隧道衬砌结构的车振动力响应.结果表明:近接基坑开挖会造成隧道掌子面的非对称变形,离开挖中心越近非对称变形越明显;随着近接开挖距离的增加,这种非对称变形逐渐趋于缓和,其中隧道靠近开挖侧的隧道拱脚、拱腰和拱顶区域可作为施工期间既有隧道的重点监测部位;隧道左右两侧帮底部区域相对拱顶区域而言受到列车振动影响较大,列车靠近开挖侧行驶时隧道衬砌结构动力响应比远离开挖侧行驶时大.

Study on settlement deformation of railway tunnel under approaching excavation and train vibration load

The unloading effect of excavation near a railway tunnel is seen to not only create additional stress and deformation on the tunnel, but as well affect the dynamic response of tunnel under train vibration load. This paper considered different approaching distances to study the law governing the settlement deformation of tunnels and utilized the vibration load empirical formula to simulate the wheel-rail excitation force. Finite difference analysis software FLAC^3D was used to analyze the dynamic response of tunnel lining under different approaching distances. The results show that the excavation causes asymmetric deformation of the tunnel section, the deformation becomes more and more evident as it gets closer to the center of excavation. It is further demonstrated that as the excavation distance increases, the asymmetric deformation gradually weakens. The arch spring, haunch and vault may serve as key monitoring locations. The influence of train vibration is greatest on the arch springing, and the dynamic response on the side near the excavation is greater than on the far side.