铁路隧道基底脱空条件下的动力响应分析

列车荷载作用是诱发在役隧道基底病害的主要原因。为分析隧道基底脱空条件下对列车荷载的响应问题,以某铁路隧道工程Ⅲ级围岩正常断面为对象,通过现场在隧道铺底顶面埋设压力盒,对铺底混凝土层受力进行测试;在此基础上,通过数值计算,重点分析列车荷载作用下基底不同脱空长度下的基底中心线、轨道处与轨枕端头处的应力分布规律及铺底顶面振动特性。结果表明:在铺底顶面,动压力在轨道、轨枕端头处与基底中心线处分别为80,20 k Pa和60 kPa。经计算模拟,基底存在40 cm与80 cm宽脱空区时,在轨枕端头处、轨道处及中心线处应力规律基本一致,在脱空区处应力出现先减小再增加现象,且轨道处突变最大,脱空区侧壁处存在应力集中现象,脱空区影响深度范围约2 m。80 cm宽脱空区在数值上与40 cm宽脱空区相比,基底动应力、铺底顶面加速度与振动位移的最大增幅分别为50%、30%和3%。

Dynamic Response of Base Void Area of Railway Tunnel

The train load is the main cause of induced basal defects in the tunnel.In order to analyze the response of the base void area to train loads,the normal section of Class Ⅲ surrounding rock of a railway tunnel project is taken as the research object.The pressure box is buried on the top surface of the tunnel bedding to test the stress of the concrete floor.The stress distribution law of the center line of the tunnel bottom,the track line and the end of the sleeper,and the bottom surface vibration characteristics are analyzed under different loads.The results show that the dynamic pressures on the top tunnel bedding are 80 kPa,20 kPa and 60 kPa respectively at the track,the end of sleeper and the bedding center.The calculation and simulation indicate that when 40 cm and 80 cm wide void areas exist at the tunnel bedding,the stresses remain the same pattern at the above mentioned three places,and the stress increases first and then decreases in the void area.The stress changes abruptly at the track and concentrates at the sidewalls of the void area,and the affected depth of the void area is about 2 m.The numerical comparison between 80 cm wide void area and 40 cm wide void area shows that the maximum amplification reaches 50%,30% and 3% respectively in terms of base dynamic stress,acceleration and vibration displacement.