Pile-supported embankment is popularly used for constructing high-speed railways on soft soils. With train running at high speed, the dynamic load on the pile top generated by the train passages increases noticeably. To keep the long-term settlement of the railway track within a reasonable range, it is necessary to investigate the settlement of piles in soils simultaneously subject to the monotonic load caused by the weight of the track structure and embankment as well as the cyclic load caused by the train passages. In this paper, model tests on piles in silt soil under combined monotonic and cyclic loading were conducted. The behavior of a pile in saturated silt was investigated by measuring pile settlement, soil pressure on the pile surface, and pore water pressure in the soil adjacent to the pile. Based on the model testing results, the ratio of the mean value of cyclic load to the ultimate bearing capacity of the pile (P_m/P_u) and the ratio of the half amplitude of the cyclic load to the ultimate bearing capacity of the pile (P_cyc/P_u) were identified as the main factors dominating the development of pile settlement. A higher P_cyc/P_u leads to faster accumulation in the pile settlement, and a higher P_m/P_u facilitates this process. A chart with three zones determined by the combination of P_cyc/P_u and P_m/P_u has been proposed to distinguish the settlement trends of the piles: stable zone, metastable zone and unstable zone. The combination of P_cyc/P_u and P_m/P_u located in the stable zone generates very small settlement. Moreover, for the loading combination in the metastable zone, an analytical model was proposed to predict the cyclic pile settlement subject to cyclic load with large cycles. The advantage of the model is that the coefficient of friction at the pile surface and the cyclic strain degradation parameter are incorporated. Finally, a case study is presented to demonstrate the application of the proposed chart and the prediction method on cyclic pile settlement in the design of piled embankment of high-speed railways.

桩承式路堤通常用于在软土上修建高速铁路。随着火车高速运行，火车通道在桩顶产生的动载荷显着增加。为了使铁路轨道的长期沉降保持在合理的范围内，有必要同时研究桩在土壤中的沉降，该沉降同时承受由轨道结构和路堤的重量引起的单调载荷以及所引起的循环载荷通过火车通道。本文进行了单调和循环荷载作用下粉土中桩的模型试验。通过测量桩沉降，桩表面的土压力和桩附近土壤的孔隙水压力，研究了桩在饱和淤泥中的行为。根据模型测试结果，P _m / P _u）以及循环荷载的半振幅与桩的极限承载力之比（P _cyc / P _u）被确定为决定桩沉降发展的主要因素。较高的P _cyc / P _u导致桩沉降中的堆积更快，而较高的P _m / P _u促进了这一过程。由P _cyc / P _u和P _m / P _u的组合确定的具有三个区域的图表有人提出区分桩的沉降趋势：稳定区，亚稳区和不稳定区。的组合P _CYC / P _ù和P_米/ P _ù位于稳定地带的沉降很小。此外，对于亚稳态区域的荷载组合，提出了一种分析模型来预测大周期荷载作用下的循环桩沉降。该模型的优点是将桩表面的摩擦系数和循环应变退化参数结合在一起。最后，通过实例研究证明了所提出的图表和预测方法在循环桩沉降计算中的应用。