列车振动下隧道基底合理结构型式的研究

采用弹塑性二维非线性有限元法分析了隧道及周围环境在列车振动下的响应，分析中考虑了仰拱的不同结构形式、不同曲率、不同刚度、仰拱与边墙的不同联结方式。根据分析得到的仰拱中和仰拱下部围岩中的应力分布图，评价了仰拱对列车振动反应的影响，认为列车振动下隧道基底结构较为合理的结构形式和措施为：(1)采用矢跨比较大的仰拱；(2)采用较厚的隧底填充；(3)将仰拱、隧底填充和道床用同级混凝土浇灌成为一个整体结构；(4)采用各种排水措施排除隧底以下积水，避免长期振动下引起的岩土液化；(5)采用注浆和安设锚杆加固基底围岩，以提高其强度。

STUDY ON RATIONAL STRUCTURE OF RAILWAY TUNNEL BED UNDER DYNAMIC VIBRATION LOAD

Based on in-situ measurements carried out by the authors at Jinjiayan railway tunnel,a simulated vertical dynamic load of passing trains is put forward. 2D finite element method is adopted to analyze the dynamic responses of tunnels and their surrounding masses to the traffic vibration. In the analyses various structure types,various curvatures,various stiffnesses of the invert and various types of connection of the invert with side wall are considered. The stresses of invert and stress distribution of the surrounding masses under the invert are obtained,and the effect of the structure type of invert on vibration responses is assessed. As a result,a rational structure type of railway tunnel under dynamic vibration load is put forward. The effective measures and rational structure for the railway tunnel bed under dynamic vibration load are that (1) the tunnel invert with the larger ratio of rise to span is recommended,(2) the filling on invert is as thick as possible,(3) a entire rigid structure should consist of invert,filling and road bed with help of concrete of the same strength,(4) the water stocked under the invert must be drained away to avoid rock-soil liquefaction under long-term vibration,and (5) grouting and bolting should be employed to reinforce the surrounding rock masses under invert.