云桂高速铁路新型全封闭路堑基床动响应特性研究

膨胀土地区路堑基床病害是高速铁路建设中倍受关注的问题。结合云桂高速铁路工程实际，以典型膨胀土新型路堑基床为基础，借助有限差分软件FLAC3D，建立了三维路堑基床动力分析模型，探讨了列车荷载作用下新型全封闭路堑基床动力特性，并结合现场试验进行了分析。分析结果表明：数值模拟结果可较好地反映基床动响应变化规律，且与现场实测变化趋势相同；基床竖向动应力随深度呈指数型衰减，基床竖向动位移随深度呈幂函数型衰减；路基面动位移值为0.95 mm，满足高速铁路规范要求；基床动响应特征受服役环境影响显著，浸水条件下会引起基床表层动应力及振动速度增大；铺设防排水结构层可改善基床内的动应力分布，并减小路基面的动位移及增强基床抗振性能。研究成果可为膨胀土地区高速铁路工程实践及理论研究提供参考。

Dynamic response of the new fully-enclosed cutting subgrade of Yun-Gui high-speed railway

The subgrade defect of expansive soil is of main concern in high-speed railway construction. Based on the monitored data of the cutting subgrade of Yun-Gui high-speed railway and using software FLAC3D, a three-dimensional dynamic analysis is performed to study the dynamic behavior of the cutting subgrade under the moving train load. It is shown that the dynamic response can be described by numerical model and the predicted variation is consistent with the observations. The vertical dynamic stress of subgrade is exponentially attenuated and the variation of vertical dynamic displacement with depth follows a power law. The dynamic displacement value of railway surface is 0.95 mm which satisfies the requirement of high-speed railway specification. The effect of working conditions on dynamic responses of subgrade is significant. The dynamic stress and vibration velocity of subgrade surface increase due to immersion condition. Laying waterproof and drainage structure layer will improve dynamic stress distribution, reduce dynamic displacement of railway surface and enhance anti-vibration performance of subgrade. The conclusions can provide references for engineering practice and theoretical research of high-speed railway in expansive soil area.