砂土拱效应的挡板下落试验及机理研究

土拱效应对考虑拱效应时土压力的计算非常重要，而目前对土拱效应的形成机理认识还不深刻。通过自行设计的室内挡板下落试验对砂土拱效应的问题进行了试验研究。得到了不同的土体埋深情况下，随挡板下移挡板上土体重量、箱内土体的应力和侧压力系数的变化规律。试验结果表明，挡板微小的位移挡板上土体的重量就会快速降低；随着挡板继续下移挡板上土体重量降低的趋势逐渐减缓，认为挡板下移2.5 mm时上部土体达到临界状态；随挡板下移箱底挡板上部中心线上的竖向土压力减小，挡板两侧上部土体的竖向土压力增大；挡板上部中心线上的侧压力系数明显增大。通过土体内的应力变化规律对砂土拱效应的形成机理进行了分析。

On baffle drop test and mechanism of sand arching effect

Soil arching effect is very important to the soil pressure calculations. The problem of the sand arching effect was studied through the indoors baffle drop test designed by the authors. Along with the baffle’s drop, the sand’s weight on the baffle, the sand’s stress and the lateral pressure coefficient that under different buried depths of sand in the box were characterized. It is shown that the sand’s weight on the baffle reduces quickly when the baffle has a small displacement. The sand’s weight on the baffle reduces slowly when the baffle drops gradually. We consider that the sand reaches the critical state when the baffle’s displacement is 2.5mm. While the baffle drops, the vertical soil pressure reduces in the central line on the top of the baffle and the vertical soil pressure increases in the line on the top of the baffle’s sides. Lateral pressure coefficients in the central line on the top of the baffle increase obviously. Finally, the formation mechanism of the sand arching effect was analyzed through the stress variety regularities in the sand.