The design of rail tracks is often challenged by the highly compressible behaviour of soft estuarine clays over which they must pass. It is prudent that the realistic long-term behaviour of subgrade materials under repeated loading applied by fast moving heavy haul trains is properly understood. One feature that should not be ignored when estimating the long-term performance of track foundations is the continuous principal stress rotation (PSR) induced by moving wheel loads. The main purpose of this research is to combine the traditional cyclic triaxial test results (fixed axes, no PSR) with those obtained from the dynamic hollow cylinder apparatus (allowing PSR) to examine the relative influence of cyclic stress ratio (CSR) and frequency on the behaviour of soft subgrade subjected to simulated heavy haul train loading. Employing these two types of equipment applying contrasting stress path regimes, a series of cyclic undrained laboratory tests was conducted on reconstituted sandy clay specimens at varying frequencies (f = 0.1–1 Hz) and cyclic stress ratios (CSR = 0.2–0.3). The hollow cylinder test results have shown that higher CSR values and lower frequencies induce greater permanent deformations and excess pore water pressures at a given number of loading cycles (N). For CSR = 0.2, pore pressures and axial strains were found to increase even after a large number of cycles (N = 50,000). However, when the higher CSR value of 0.3 was imposed, the soil failed in less than 300 cycles by reaching 5% of axial strain. Undoubtedly, PSR adversely affected the accumulation of axial strains and soil degradation, whereas in contrast, the development of pore water pressure was less influenced by PSR.

铁路轨道的设计经常受到软河口粘土必须通过的高可压缩性的挑战。谨慎地理解，路基材料在快速移动的重载列车施加的反复载荷下的实际长期行为已得到适当理解。估算轨道基础的长期性能时，不应忽略的一项功能是由移动车轮载荷引起的连续主应力旋转（PSR）。这项研究的主要目的是将传统的循环三轴测试结果（固定轴，无PSR）与从动态空心圆柱体设备获得的结果（允许PSR）结合起来，以研究循环应力比（CSR）的相对影响。）和频率对在模拟重载火车荷载作用下软基的性状的影响。利用这两种类型的设备采用相反的应力路径制度，在不同频率（f  = 0.1-1 Hz）和循环应力比（CSR  = 0.2-0.3）下，对再生的砂质黏土样品进行了一系列循环不排水的实验室测试。中空圆柱体测试结果表明，在给定的加载循环次数（N）下，较高的CSR值和较低的频率会引起较大的永久变形和过多的孔隙水压力。对于CSR  = 0.2，即使经过大量循环（N = 50,000）。但是，当施加更高的CSR值0.3时，土壤在不到300次循环中破坏，达到轴向应变的5％。毫无疑问，PSR不利地影响了轴向应变的积累和土壤退化，而相比之下，PSR对孔隙水压力的发展影响较小。