竖向条形锚板水平拉拔承载规律试验研究

Experimental study on horizontal pull-out bearing law of vertical strip anchor plate

针对竖向条形锚板的拉拔承载研究存在人为区分浅埋、深埋,且界定标准及对力学模型的对称性认识不统一等问题,为了理清锚板拉拔承载随埋深的演化机理,基于数字照相测量技术对砂土中竖向条形锚板的水平拉拔问题开展模型试验研究,就拉拔极限承载力及板前土体位移变形特性随埋深比的变化规律进行分析。试验研究采用自制试验装置开展了14种埋深比工况下的水平拉拔试验,并获得了相应的荷载位移曲线。试验过程中对板周区域进行拍摄,并通过数字图像分析技术构建拉拔过程中板周土体的位移场。结果表明:中密砂中竖向条形锚板的水平拉拔极限承载力随着埋深比的增加而增大,速率由快趋缓,归一化后的承载力比可用埋深比的二次多项式进行表达。随着埋深比的增大,极限拉拔下板前砂土的位移场形态总体上表现出由非对称逐渐向对称连续变化的规律,并可用上下包络角来反映;上包络角基本不随埋深比发生变化,始终保持在(π/4+φ/2)+π/2左右;下包络角则随着埋深比的增加非线性增大,并最终趋于和上包络角相等,范围介于π/2到(π/4+φ/2)+π/2之间。研究成果可为条形锚板水平极限拉拔力学模型的构建提供新的依据。

Aiming at the problems in the study on the pull-out bearing of the vertical strip anchor plate,i.e.artificial differentiation of shallow and deep buried types,non-unified understanding of both the defining standard and the symmetry of mechanical model,etc.,a model experimental study on the horizontal pull-out behavior of the vertical strip anchor plate in sandy soil is made based on the digital photogrammetric surveying technique for clarifying the evolution mechanism of the pull-out bearing capacity of the anchor plate along with the buried depth,in which the ultimate pull-out bearing capacity and the changing law of the deformation and displacement characteristics along with the ratio of the buried depth are analyzed herein.In the experimental study,the horizontal pull-out experiments under the working conditions of 14 buried depth ratios are carried out with the relevant self-made apparatus,and then the corresponding load-displacement relationship curves are obtained.During the experiment,photograph is taken on the area around the plate,while the displacement field of the soil mass around the plate during the pull-out process is built up through the digital image analysis technique.The result shows that the ultimate horizontal pull-out bearing capacity of the vertical strip anchor plate in medium dense sand increases along with the increase of the buried depth ratio,while the increasing rate gradually slows down,for which the normalized bearing capacity ratio can be expressed by a quadratic polynomial of the buried depth ratio.Following with the increase of the buried depth ratio,the pattern of the displacement of the sandy soil in front of the plate under the ultimate pull-out force generally exhibits the law of the continuously changing from asymmetry to symmetry,which can be reflected by both the upper and lower envelop angles.The upper envelop angle basically does not change with the buried depth ratio and remains the value around(π/4+φ/2)+π/2;the lower envelop angle nonlinearly increases with the buried depth ratio fromπ/2 to(π/4+φ/2)+π/2 and finally tends to equal with the upper one.The study result can provide a new basis for building up the mechanical model for the ultimate horizontal pull-out capacity of the vertical strip anchor plate.