高速铁路膨胀土路堑全封闭基床动力特性现场试验

膨胀土路堑基床病害是铁路建设中的难题之一。在分析膨胀土地区路堑基床病害特点和产生机理基础上,开展了半刚性防水结构层研发和全封闭基床设计工作。为研究新型基床结构的动力特性,在云桂铁路典型膨胀土路段填筑了100 m全封闭基床试验段,并进行大型现场激振试验。试验结果表明：①动应力、速度和加速度大小与基床服役环境有关,基床浸水后三者在干燥状态的基础上均出现不同幅度增大；②路基面动位移随距离的增加呈幂函数型衰减,其衰减拟合曲线函数表达式为y=0.562x^(-0.37)；③基床动应力与激振频率关系曲线存在“双峰”现象,峰值频率分别为10 Hz和18 Hz；④激振频率位于16～21 Hz范围内时,速度和加速度随频率增加而迅速增大,其余频段二者随频率的变化不明显。

In-situ tests on dynamic character of fully-enclosed cutting subgrade of high-speed railways in expansive soil areas

The subgrade defect of expansive soil cutting is one of difficult problems in railway construction. Based on the analysis results of the character and mechanism of subgrade defects, semi-rigid water proof structural layer is studied, and fully-enclosed subgrade is designed. In order to study the dynamic character of this new type of railway subgrade, a 100 m-long fully-enclosed subgrade is constructed in typical expansive soil cutting section of Kunming-Nanjing high-speed railway, and in-situ dynamic tests are carried out. The results show that: (1) The dynamic stress, velocity and acceleration are affected by the working conditions. Compared to those under the dry conditions, all the three dynamic indexes become larger when the surface of subgrade is soaked. (2) The dynamic displacement of subgrade surface decreases with the increasing distance, and the attenuation curve can be fitted by power function: y=0.562x^(-0.37). (3) The relation curve between dynamic stress and excitation frequency has double peak phenomena, and the peak frequencies are 10 and 18 Hz, respectively. () The excitation frequency spectrum is 16～21 Hz when the velocity and acceleration increase rapidly.