土工格栅-砂土界面特性的拉拔试验研究

Pull-out test of interface characteristics between geogrid and sand

为研究筋-土界面摩擦特性,借助双向格栅与砂土的中型拉拔试验,研究界面正应力、横肋百分比、格栅宽度和拉拔速率对筋-土界面作用机理和格栅横肋受力的影响.研究结果表明,随着界面正应力的增加,筋材抗拔能力显著增强,单宽拉拔力达到格栅极限抗拉强度时拉拔位移变小;由于砂土对格栅的挤压作用,格栅横肋分布越均匀越有利于筋材受力,界面摩擦力占总拉拔力的比值随横肋百分比的增加而减少,相同拉拔位移下较窄格栅拉拔力略小于较宽格栅;格栅纵向应变沿长度方向先增后减,应变峰值位置随着拉拔力的增加逐渐远离加载端,表明拉拔过程中格栅的受力具有传递性和不均匀性,且最大值受筋材拉拔变形的影响逐渐向筋材中部移动.

In order to study the friction characteristics of the reinforcement-soil interface,the effects of normal stress,percentage of transverse ribs,. geogrid width and pull-out velocity on the interaction mechanism of reinforcement-soil interface and the forces acting on the transverse ribs of geogrid are studied by means of the middle-scale pull-out test of the bidirectional geogrid and soil. The results show that with the increase of the normal stress of the interface,the pull-out resistance of the ribs increases significantly and the pull-out displacement becomes smaller when the single-width pull-out force reaches the ultimate tensile strength of the grid. Due to the squeezing effect of sand on the geogrid,the more uniform distribution of the cross-ribs of the geogrid is,the more favorable the force of the reinforcement is;the ratio of the interfacial friction to the total pull-out force decreases with the increase of the percentage of the transverse ribs,and the pull-out force of the narrower geogrid is slightly smaller than that of the wider grid under the same pull-out displacement. The longitudinal strain of the geogrid increases first and then decreases in the length direction,and the strain peak position gradually moves away from the loading end as the pull-out force increases,which indicates that the force acting on the geogrid is the transferable and inhomogeneous during the drawing process,and the maximum value is gradually moved toward the middle of the reinforcement due to the influence of the drawing deformation of the reinforcement.