中—强膨胀土地区铁路路堑基床动静态特性模型试验

为研究以中—强膨胀土为地基的高速铁路路堑基床在不同服役环境下的动静态特性，在实验室内进行1∶1大比例尺模型试验，分别对基床在干燥状态、降雨和地下水位上升3种服役环境下以4 Hz频率进行100万次激振，监测路堑基床不同位置的动态响应和变形规律。结果表明：轨道正下方位置基床范围内的动应力主要受服役环境影响，与激振次数关系不大；动应力沿深度的衰减曲线近似成二次曲线型；膨胀土路堑基床变形受服役环境的影响大于振动次数；干燥状态和降雨时，基床变形随着振动次数的增加先增大后趋于稳定，地下水位上升时，基底膨胀土膨胀变形，并引起基床产生回弹变形；基底膨胀土干缩湿胀过程中的“过程性变形差”会造成轨面标高反复变化，极大的增加线路维护工作量。

Model tests on static and dynamic performances of cut subgrade of railways in medium-strong expensive soil area

In order to study the static and dynamic performances of cut subgrade of high-speed railways in medium-strong expensive soil area, model tests with a large scale of 1∶1 are performed. A cyclic load with frequency of 4 Hz and excitation of 1000000 times is imposed on the subgrade model under three kinds of working conditions (dry, raining and groundwater level rise). The results show that the dynamic stress in the subgrade beneath the track is mainly affected by the working conditions and not significantly affected by the vibrating number. The dynamic stress attenuation curve is conic in the vertical direction. The dynamic deformation is affected by the working conditions and vibrating number, that is, with the increase of the vibrating number, the deformation increases under the dry and raining conditions at first and then tends to be stable, and the subgrade rises because of the swelling deformation of expensive soil when the groundwater level increases. The in-process deformation difference is induced during the asynchronous swelling or shrinkage deformation process of expansive soil and causes the rail surface elevation to change repeatedly, and the maintenance work for track lines is greatly increased.