露天矿排土场土工格栅加固机制试验研究

Experimental research on reinforcement mechanism of geogrid in open-pit dump

运用底摩擦试验方法对比研究多种条件下土工格栅加固排土场的失稳过程,基于图像散斑分析与测点追踪技术获取土工格栅加固排土场的位移场和应变时程,重点分析排土场的破坏模式、稳定性以及土工格栅加固机制。研究结果表明:(1)未加固或土工格栅长度不足时,排土场发生深层破坏,破坏机制为整体式圆弧型滑动,剪切效应自下而上进行传递;全长土工格栅加固后排土场破坏模式由整体破坏转换为局部破坏,排土台阶更陡情形边坡浅层的剪切效应更显著。(2)排土场变形可分为3个阶段:第I阶段为均匀变形阶段,测点位移较小;第Ⅱ阶段为变形局部化阶段,部分测点产生了位移加速,模型内部产生了滑裂面;第Ⅲ阶段为破坏阶段,测点位移产生分叉现象,滑体测点位移持续增加,稳定区域测点位移趋于恒定;土工格栅对排土场变形具有显著的抑制作用。(3)采用初始开裂时间和局部破坏时间作为评价指标研究了土工格栅加固排土场的稳定性。相同排土场几何要素条件下,土工格栅加固能够明显提高排土场稳定性。此外,通过布设土工格栅能够在确保稳定性的前提下有效提高排土场容积,以模型A1和B1为例,土工格栅加固后排土场稳定性提高的同时容积扩大约6.33%。(4)对于基底条件较差的高陡排土场,建议采用全长土工格栅的加固方式;对于基底条件较好、堆置高度小的排土场,可根据实际情况,适当缩减土工格栅的铺设长度以节省材料成本。相关成果对于排土场稳定和增高扩容、节省占地面积具有指导意义。

A series of base frictional tests were conducted to study the failure process of mine waste dump reinforced with geogrid under various conditions.By the image speckle analysis and point-tracking technology,the displacements and strains of mine waste dump were obtained,and the failure mode,stability of the dump and mechanism of the geogrid were analyzed.The results show:(1)When there is no geogrid or the length of the grogrid is insufficient,the mine waste dump will suffer deep failure,showing an integral arc sliding from bottom to top.When the full-length geogrid is used,the failure mode of the dump changes from the overall failure to local failure,and the shear effect of the shallow layer of the slope becomes more significant when the bench slope is steeper.(2)The deformation process of the dump can be divided into three stages.The first stage is the uniform deformation stage,and the displacement of the measuring points is small.The second stage is the deformation localization stage,in which some measuring points produce displacement acceleration and slip crack forms inside the model.The third stage is the failure stage,where the displacement of the measuring point shows a bifurcation phenomenon.To be specific,the displacement of the measuring point of the sliding body continues to increase,while the displacement of the measuring point in the stable body tends to be constant.The geogrid has a significant control effect on the deformation of the dump.(3)The initial cracking time and local failure time are taken as the evaluation index to study the stability of geogrid-reinforced dump.The geogrid can be used not only to improve the dump stability,but also to expand the volume of the dump.Taking Model A1 and B1 in this study as examples,the dump expands the volume by about 6.33%with geogrid reinforcement under the promise of ensuring stability.(4)For high and steep dumps with weak foundations,we recommend using full-length geogrid;however,for dumps with fine foundations and smaller heights,the length of geogrid can be reduced to save costs according to the practice.The results have guiding significance for the stability and expansion of the dump and saving the land area of the mining area.