高铁桩网复合结构路基长期运营沉降模型试验研究

Model tests on the long-term settlement of pile-net composite structure subgrade for high-speed railways

高铁路基沉降控制是保证列车安全性和舒适性的重要因素。随着高铁运营时间增长,软土地区高铁路基长期沉降问题越来越引起关注。针对京沪高速铁路徐沪段某试验段,开展了桩网复合结构路基长期循环动态加载物理模型试验,获得了路基沉降、桩土应力分担及桩身轴力分布的变化规律。试验结果表明:在初始1000次加载时,路基沉降随加载次数增加明显,之后达到稳定;桩上部位置土体变形大于桩身变形,桩侧呈现负摩阻力,中性点位于距桩顶约2/3桩长位置;桩身轴力随加载次数增加而增大,说明桩分担荷载增加,当达到4万次加载后,轴力随加载次数增加不再明显。

The settlement control of the high-speed railway subgrade plays an important role in comfortable and safe running of high-speed train. With the growth of operation time, the long-term settlement of railway in soft subgrade has been concerned. Based on the Xuzhou-Shanghai section of Beijing-Shanghai high-speed railway, the model tests on the pile-net composite structure subgrade under dynamic loading were carried out, and the variation rules of subgrade settlement, stress ratio of pile-soil, and axial force distribution were obtained. The results show that in the first 1000 loading cycles, the subgrade settlement increases with loads significantly, and then it reached a constant value. The deformation of soil is larger than that of pile at the upper pile position, the negative friction resistance appears, and the neutral point of pile is located near 2/3 pile length away from the pile top. The axial force of pile increases with the increase of the cycles of loads, when the loading cycles reach 40000, the axial forces doesn't obviously increase.