桩承式路堤土拱效应有限元研究

Study of soil arching in piled embankment with FEM

路堤下设置的带承台桩,除了承担承台上方的填土重量外,通过土拱效应还承担桩间土上方的部分重量。将填土重量的大部分传递到地基深部,既增加了路基的稳定性,又减小了路基的沉降。上海国际赛车场建造在软土地基上,为了满足工程需要,除使用了EPS轻质填筑材料外,还在填筑高度较高的地段采用了桩承式路堤作为地基加固方式。为了深入研究土拱效应的工作机制,对上海国际赛车场路堤桩的承台与承台间土压力分布进行了原位测试,并结合实际工况进行有限元分析。结果表明:除了承台上方的土压力相对承台间土有应力集中现象外,承台边缘相对承台中部也有应力集中现象。对EPS的加入和桩体性质的各项参数对于土拱效应产生的影响进行了分析。

A pile-cap foundation system is an effective way to support an embankment in order to minimize total settlement.Due to the higher stiffness of the piles in relation to the surrounding soft soil,the vertical stresses from the embankment are concentrated on the piles.Soil arching develops as a result of differential settlements between the stiff pile caps and the soft ground between them.The three-dimensional arches span the soft soil and the applied load is transferred onto the piles and then the firm-bearing stratum.This research was initiated from the Shanghai F1 speedway project.Shanghai F1 speedway has been built on the typical soft ground of Shanghai.The fill of Shanghai speedway includes not only the lime fly-ash which has been widely used but also EPS which aimed to alleviate the total load;piled embankments method is employed at the region where the height of fill is relatively high.The field test has been done in Shanghai F1 speedway to investigate the distribution of earth pressure on the cap and between the caps.In addition,numerical method is used to in comparison with the field test results.The results show that the earth pressure obtained in the soil right above the cap is relatively higher than in the soil surrounding the cap.And the earth pressure distribution shows the same way for the soil lies on the edge of cap and the centre of cap.The influence of EPS and piles character on soil arching is discussed.