桩承式路堤土拱效应形成机制离散元模拟

针对桩承式路堤,分别建立二维和三维离散元分析模型,开展土拱形成过程数值模拟。从细观角度研究不同路堤高度条件下桩承式路堤土拱形态和荷载传递机制,获得土拱效应充分发挥条件下的土体沉降模式,其模式呈现为椭圆形拱状。二维分析结果表明,当路堤填土高度达到一定值时,其高度约为0.8倍桩净距。由于二维土拱模型只能反映一个截面上的土拱效应,因而高估了路堤荷载传递效率。相比二维Trapdoor分析结果,三维条件下土拱效应充分发挥时所需的桩-土差异沉降更大,桩顶和桩间土压力随差异沉降的变化速率更慢,荷载传递效率更低且受填土高度影响更高。

Discrete Element Simulation of the Formation Mechanism of Soil Arching in Piled Embankment

Two-dimensional and three-dimensional discrete element models were established to study the formation of soil arching in a pile-supported embankment. The shape of soil arch and the load transferring mechanism of pile-supported embankment under different embankment height were investigated from microscopic point of view, and the obtained settlement profile of soil shows an elliptical mode. In the two-dimensional case, the height of soil arch is about 0.8 times of the pile spacing, as long as the embankment fill is thick enough. Since two-dimensional model can only reflect the soil arching effect in a cross section, the load transfer efficiency of the embankment will be overestimated. Compared with the two-dimensional case, the full mobilization of soil arching under three-dimensional condition requires a larger differential settlement, the changing rate of the soil pressures on the pile and subsoil with differential deformation becomes slower, the load transfer efficiency is lower, and the soil height becomes more affected by the embankment height.