隧道下穿高速公路施工引起的道路变形分析

隧道下穿高速公路或铁路是隧道建设中的技术难点之一,因设计或施工不当引起的路面变形甚至坍塌,将会导致巨大的经济损失和不良的社会影响。文中以杭州市第二水源千岛湖配水工程为背景,结合隧道在不中断路面交通情况下穿越S305省道的工程特点,采用有限元软件PLAXIS 3D对该标段的开挖进行数值模拟,研究隧道下穿高速公路施工引起的围岩、路面变形机理。通过对开挖过程中不同交通荷载工况下的地层扰动情况进行对比分析,得出交通荷载-地层变形的关系,并进一步探究一般交通荷载工况下的地层变形规律。利用建立的有限元模型对不同的支护方案进行计算分析,对比加固效果,优化支护参数,确定施工工艺,并与施工期间的现场监测值对比,发现结果基本接近。研究表明:随着交通荷载的增大,路面最大沉降和拱顶最大沉降均呈先缓慢增长,后快速增长的趋势;粉砂岩地层采用全断面开挖的施工方法以及自进注浆锚杆和注浆小导管超前支护相结合的加固方式,在有效控制沉降变形的同时,还能加快施工进度,可供类似工程借鉴。

Analysis of Road Deformation Caused by Tunnel Construction underpass Expressway

Tunnel under the highway or railway is one of the technical difficulties in the tunnel construction,deformation or even collapse of roads caused by improper design or construction will lead to huge economic loss and adverse social impact.This paper is based on the Qiandao Lake Water Distribution Project in Hangzhou City,combined with the engineering characteristics of the tunnel passing through the S305highway without interruption of the traffic on the road,the finite element software PLAXIS 3Dis used to simulate the excavation of the section and to study the deformation mechanism of surrounding rock and pavement due to the construction of the tunnel under the expressway.Through the comparison and analysis of stratum disturbance under different traffic load conditions during excavation,the relationship between traffic load and stratum deformation is obtained,and the stratum deformation law under general traffic load conditions is further explored.The established finite element model is used to calculate and analyze different support schemes,compare reinforcement effect,optimize support parameters,determine the construction process,and compared with the on-site monitoring during construction,the results are basically similar.The research shows that with the increase of traffic load,both the maximum settlement of the road surface and the maximum settlement of the dome show a slow growth first and then a rapid increase;the construction method of full-face excavation in the siltstone stratum and the reinforcement method combining the self-injection grouting anchor and the grouting small pipe advance support can effectively control the settlement deformation and also accelerate the construction progress,which can be used for similar projects.