桩承式挡墙路堤三维土压力分布与变形特性试验

Experimental investigation of three-dimensional earth pressure distribution and deformation patterns of piled embankments with retaining wall

为了深入探讨桩承式挡墙路堤中的三维土压力分布及变形特性,采用自制的阵列式多活动门装置,选取路堤高度、桩间净距等参数,并考虑桩间土均匀下沉与非均匀下沉的情况,开展10组模型试验。通过粒子图像测速技术对路堤填砂颗粒位移进行监测,采用自制的荷载计与土压力盒量测桩间土、桩顶和挡墙土压力。试验结果表明:路堤变形存在三角扩展和塔形升高2种模式;应力折减比最小值与残余值均随路堤高度的增加而减小,但同时土拱效应衰减(桩间土应力恢复)速度、衰减达到稳定对应的沉降量均增加,非均匀下沉对土拱效应峰值存在削弱作用,但是对土拱效应残余值影响不大;土拱效应发挥导致土压力在桩顶和路堤中部一定高度位置产生集中。三角扩展模式的土拱效应发挥较弱,塔形升高模式中土拱效应在桩间土下沉过程中得以加强并保持了较高的水平。桩承式挡墙路堤三维土压力分布与变形随桩间土下沉演化的研究成果可为桩承式挡墙路堤设计提供参考。

To investigate the three-dimensional earth pressure distribution and deformation characteristics of piled embankments with retaining wall,ten groups of model tests considering the embankment height,the clear distance between piles as well as even and uneven settlements of soil between piles were carried out using a multiple trapdoor test setup. The displacement of sand fill was measured adopting particle image velocimetry technique(PIV),and the soil pressures between the piles,on the pile top and on the retaining wall were monitored by self-made load gauges and earth pressure cells. The test results show that the embankment has two deformation patterns including triangle expanding pattern and tower-shape development pattern. With increasing the embankment height,the minimum and residual values of the stress reduction ratio decrease,while the retrogression rate(stress recovering rate) of the soil arching effect and the settlement for the residual stage increase. The uneven settlement weakens the peak soil arching effect but has little influence on the residual value of the soil arching effect. The soil arching effect in the embankment fill induces the concentration of the earth pressures at the pile top and a certain height in the central part of the embankment. The soil arching effect in the triangular expanding pattern is weaker than that in the tower-shaped development pattern. The soil arching effect in the tower-shaped development pattern is strengthened and maintained at a high level during the settlement. This study on the evolution of three dimensional distribution of the earth pressure and deformation with the settlement between piles provides a basis for the design of pile supported retaining wall embankment.