循环荷载下低填方桩承式路堤动力响应分析

Dynamic response analysis of a low-filled piled embankment under cyclic loading

低填方桩承式路堤在交通荷载下的动力响应特性与路堤的承载能力及其稳定性密切相关。基于前人的室内模型试验,采用PFC2D软件建立了桩承式路堤离散元数值分析模型;采用数值双轴试验、数值单向压缩试验分别对路堤填料和桩间土的细观参数进行了标定;同时,根据路堤荷载传递效率对模拟结果与试验数据进行了对比分析,验证了离散元数值模型的正确性及适用性。在此基础上,在低填方路堤表面施加正弦波循环荷载,并对路堤荷载传递效率、接触力分布及路堤沉降等的变化规律进行了分析。模拟结果表明:在循环荷载作用下,低填方路堤中土拱结构的承载力先逐渐弱化并最终趋于稳定;该弱化作用在宏观上表现为路堤荷载传递效率的逐渐降低,而在细观上则表现为桩顶及桩间土上方接触力差异程度的逐渐减小;同时,土拱结构的弱化将不断加剧路堤表面的不均匀沉降。

The dynamic response of a low-filled piled embankment under traffic loading is closely related to its bearing capacity and stability. In this study, a series of discrete element numerical models of piled embankments is established by using PFC2D based on the previous indoor model tests. The microscopic parameters of embankment filling and soil between piles adopted in the discrete element model are calibrated by numerical biaxial tests and uniaxial compression tests, respectively. Meanwhile, the validity and feasibility of the discrete element model are verified by comparison of load-transfer efficacy between the discrete element results and experimental data. Then, a cyclic loading in an ideal sinusoidal wave is applied to the surface of a low-filled piled embankment, and the analyses of load-transfer efficacy, distribution of contact force and embankment settlement are performed in detail. Numerical simulation results indicate that the bearing capacity of soil arching in a low-filled embankment would be gradually weakening firstly under the cyclic loading and reach a steady state finally. Specifically, the weakening of soil arching performs as the decreases of the load-transfer efficacy in macroscopic and the difference between the contact forces upon piles and soil between piles in microscopic. Meanwhile, the weakening of soil arching would result in the aggravation of differential settlement on embankment surface.