桩承式路堤中土拱效应演变规律宏细观研究

Macro and Micro Analysis on Evolution of Soil Arching Effect in Piled Embankment

基于桩承式路堤平面土拱效应研究的室内模型试验,采用PFC2D软件建立桩承式路堤颗粒流数值分析模型,通过与试验结果对比验证了该数值分析模型的正确性。首先,基于路堤自重应力荷载作用下的颗粒流数值模拟结果,验证了平面土拱效应内拱与外拱高度理论计算公式的正确性。然后从路堤中竖向应力的分布规律、应力缩减比的变化规律以及路堤中接触力的分布规律三个角度分析了路堤表面外加荷载作用下桩承式路堤中土拱效应的演变规律。研究发现:当路堤表面外加荷载由10 kPa增大至40 kPa时,桩承式路堤中的土拱效应发挥稳定;当路堤表面外加荷载由40 kPa增大至100 kPa时,桩承式路堤中的土拱结构发生了退化并有新的土拱结构形成,在宏观上表现为软土承担竖向荷载的分担比呈现增大的趋势。

Soil arching effect is the main load transfer mechanism of piled embankment.It is the key factor to analyze the load transfer and the settlement of piled embankment to correctly grasp the evolution mechanism of soil arch.Based on the model test of plane soil arching effect,the PFC2D software is used to establish the particle flow numerical analysis model of piled embankment,and the correctness of the numerical analysis model is verified by comparing with the test results.Firstly,the theoretical calculation formula for the height of inner arch and outer arch of plane soil arching is verified based on the numerical simulation results of particle flow under embankment self-weight stress.Then,the evolution law of soil arching effect in piled embankment under the external load on the embankment surface is analyzed from three aspects including the distribution of vertical stress in embankment,the variation of stress reduction ratio and the distribution of contact force in embankment.When the external load on the embankment surface increases from 10 kPa to 40 kPa,the soil arching in the piled embankment is stable.For the condition that the external load on the embankment surface increases from 40 kPa to 100 kPa,the soil arch structure in the piled embankment will degenerate and form a new soil arch structure,which shows that the vertical load carried by the subsoil presents an increasing trend.