高铁荷载下桩承式路基动力响应及土拱效应研究

土拱效应的作用机制是桩承式路堤荷载传递的关键性技术问题，然而高铁荷载作用下桩承式路堤中土拱效应的研究尚不充分。基于高铁设计规范的相关内容，建立了高铁荷载作用下桩承式路堤三维有限元分析模型，并采用已有研究结论验证了数值模型的正确性。根据该数值分析模型，首先分析了高铁荷载作用下路基的动力响应，研究了高铁荷载作用下道床和路堤不同位置处的竖向位移随时间的变化规律，以及路基中速度与加速度沿深度的分布规律。研究发现：道床和路堤表面处的竖向位移随时间变化呈倒“M”型周期变化，而路堤底部处呈“V”型周期变化；速度与加速度在路基深度范围内衰减了80%。通过变化桩间距、路堤高度以及路堤材料参数，分析其对高铁荷载作用下路堤应力和沉降发展规律的影响，进而分析其对土拱效应的影响。研究结果表明：动载作用下土拱效应依然存在，但有所减弱，动载峰值作用下减弱程度最大，谷值情况下有所恢复；桩间距和路堤高度对高铁荷载作用下桩承式路堤中土拱效应的影响较为明显，而路堤填料内摩擦角和剪胀角的影响则相对较小。

Investigation on dynamic response of subgrade and soil arching effect in piled embankment under high-speed railway loading

The mechanism of soil arching effect is the key technical problem for load transfer of pile supported embankment. However, the soil arching in pile supported embankment under high-speed railway load is not well investigated. Based on the code for design of high-speed railway, a three-dimensional finite element analysis model of pile supported reinforced embankment under high-speed railway load is established, and its correctness is verified by the existing research results. According to the numerical model, the dynamic response of subgrade under the high-speed railway load is analyzed, including the variation of vertical displacement with time at different depths of roadbed and embankment load, as well as the distribution of velocity and acceleration along the depth. The results show that the vertical displacement of the roadbed and the embankment surface changes with time in an inverted M shape periodically, while the embankment bottom changes in a V shape periodically. It is also found that the velocity and acceleration decrease by 80% along the depth of subgrade. Then, the influence of different factors including pile spacing, embankment height and the properties of the embankment fill on the stresses and settlements are comprehensively analyzed. Hence, the soil arching effect in piled embankment under high-speed railway loading can be investigated. It shows that the soil arching effect remains valid but weakened under the dynamic loading, which weakens the maximum under the peak load, while restores under the valley load. Also it is found that the influences of pile spacing and embankment height are obvious on soil arching effect under dynamic loading, while the effects of friction angle and dilatancy angle of embankment fill are relatively small.