Zhang Qishu, Leng Wuming, Dong Junli, Xu Fang
School of Civil Engineering, Central South University, Changsha 410075, China.
School of Civil Engineering, Central South University of Forestry and Technology, Changsha 410004, China.
Materials (Basel). 2022 Sep 25;15(19):6651. doi: 10.3390/ma15196651.
Poor subgrade conditions usually induce various subgrade diseases in railways, leading to some adverse influences. An innovative technology that involves installing a prestressed reinforcement structure (PRS) that consists of steel bars and lateral pressure plates (LPP) for subgrade was introduced to improve its stress field and provide compulsive lateral deformation constraints for slope. In this study, an investigation into the dynamic acceleration responses of railway subgrade strengthened according to different PRS schemes was presented using a 1:5 scale model test, aiming to explore the effects of the axle load, the reinforcement pressure, and the loading cycles on the acceleration characteristics of the subgrade. The experimental results showed that (1) after pretension of the steel bar, prestress loss occurred due to the soil creep behavior and group anchor effect, so a moderate amount of over-tension in practices would be necessary; (2) a distinctive periodical behavior of subgrade subjected to the cyclic loads was observed, the horizontal accelerations were generally less than the vertical accelerations at the same measurement heights, and the vibration energy attenuated gradually from the shoulder to the toe along the slope; (3) in the short-term tests, the peak accelerations at all measurement points had a linear correlation with the axle load, and oppositely, it showed an approximately linear decrease with the increasing reinforcement pressure; And (4) in the long-term tests, to simulate the heavy haul wagon with a 35 t axle load, the variation in the effective acceleration with loading cycles under reinforcement pressure 100 kPa initially exhibited a decrease and subsequently tended to be stable, which is apparently less than that without reinforcement pressure. Consequently, it was demonstrated that the PRS itself and increasing reinforcement pressure can effectively mitigate the subgrade vibration, and provide an appropriate alternative to improve the dynamic performance of railway subgrade under the moving train loads.
不良的路基条件通常会在铁路中引发各种路基病害，从而产生一些不利影响。为了改善路基的应力场并为边坡提供强制性的侧向变形约束，引入了一种创新技术，即安装由钢筋和侧向压板组成的预应力加固结构（PRS）。在本研究中，通过1:5比例模型试验对采用不同PRS方案加固的铁路路基的动态加速度响应进行了研究，旨在探讨轴重、加固压力和加载循环对路基加速度特性的影响。试验结果表明：（1）钢筋预张拉后，由于土体蠕变行为和群锚效应会发生预应力损失，因此在实际操作中需要进行适量的超张拉；（2）观察到路基在循环荷载作用下具有明显的周期性行为，在相同测量高度处，水平加速度一般小于垂直加速度，且振动能量沿边坡从肩部到坡脚逐渐衰减；（3）在短期试验中，所有测量点的峰值加速度与轴重呈线性相关，相反，随着加固压力的增加，峰值加速度呈近似线性下降；（4）在长期试验中，为模拟轴重35 t的重载货车，在100 kPa加固压力下，有效加速度随加载循环的变化最初呈下降趋势，随后趋于稳定，这明显小于无加固压力时的变化。因此，证明了PRS本身以及增加加固压力能够有效减轻路基振动，并为改善列车移动荷载作用下铁路路基的动力性能提供了一种合适的选择。
