格栅纵/横肋对筋-土界面拉拔特性的影响研究

Study of the Effect of Longitudinal and Transversal Ribs on Pullout Performance of Interface between Geogrids and Sand

为了研究格栅加筋土体复合材料的加筋机理,借助砂土中双向格栅的拉拔试验,综合研究了纵肋根数、纵肋长度、横肋数量和格栅裁剪方式等对筋-土界面作用特性和格栅横肋贡献率的影响。研究结果表明:无横肋时筋材拔出对应的极限拉拔力随纵肋根数增加近似呈线性增加,并随筋材单根纵肋长度的增加,筋材极限拉拔力对应的加载端位移增大;当筋材长度增加且大于临界长度时,摩擦阻力增量斜率降低;保持纵肋相同,增加横肋数量筋材极限拉拔力增加,且横肋端承阻力对拉拔力贡献率逐渐增加,受横肋位置影响横肋对筋材拉拔力贡献率的增幅逐渐降低;针对相同的50%横肋百分比,筋材裁剪方式对筋-土界面摩擦作用效果显著,格栅横、纵肋分布越均匀,格栅极限拉拔力越大,表明格栅网格均匀性是确保加筋效果的关键因素之一。

In order to study soil reinforcement mechanism of geogrid-reinforced soil composite materials,the middle-scale pullout tests were carried out. The effects of the number of longitudinal and transversal ribs of geogrids,the length of ribs and cutting modes of geogrids on the interaction characteristics of reinforcement-soil interface were analyzed in detail. The pullout test results show that the ultimate pullout forces of geogrids increase with the increasing number of longitudinal ribs of geogrids without transversal ribs and the increasing length of single transversal rib of geogrids;the ultimate pullout forces and the corresponding displacements at the loading position increased simultaneously.Once the length of the single rib was greater than the given critical length,the increasement magnitude of frictional resistance reduced. Additionally,keeping the longitudinal ribs identical,to increase the number of transversal ribs,both the peak pullout forces of geogrid and the rate of bearing resistance of transversal rib increased;the increment magnitude of contribution rate of transversal ribs,however,reduced gradually. When the rate of transversal ribs is 50%,the cutting mode of geogrids has a great effect on the geogrid-soil interface performance. The more uniform the longitudinal and transversal ribs are,the greater the ultimate pullout forces of geogrid are,which indicates that the uniformity of grid size of geogrids is one of the key factors to ensure the reinforcing effect.