加筋土结构筋-土界面特性和筋材位移变化规律试验研究

Experimental study on interface properties between geogrids and sand and reinforcement displacement distribution of reinforced soil structures based on pullout tests

基于拉拔试验研究加筋土结构筋-土界面正应力、填土压实度与含水率、拉拔速率等对筋-土相互作用特性和筋材位移变化的影响,分析筋材位移的演变规律。研究结果表明:土中筋材各点位移均不同程度滞后于加载端位移,且随与加载端的距离增加而增加,筋材位移呈非线性递减趋势;增加界面正应力、压实度或含水率,相同拉拔力下同一位置处筋材位移呈减小趋势,且距加载端越远,筋材位移受影响越小;筋材拉拔以整体拔出和拉断破坏模式为主,筋材拔出破坏时拉拔力峰值与加载端位移呈近似线性关系,且格栅拉拔力峰值与界面正应力、压实度、含水率或拉拔速率呈正相关关系;增加压实度或含水率,筋-土界面相互作用增强,筋-土界面摩擦角略有增加,但筋-土界面似黏聚力增加明显,且接近填土最佳含水率时界面似黏聚力较大。拉拔特性试验表明,加筋土工程中应严格控制填土含水率,适当的筋-土界面变形有利于发挥筋材作用。

Based on pullout tests,the effect of normal stress,compaction degree as well as water content of backfills on interaction mechanism of reinforcement-soil interface and reinforcement displacement were investigated and the evolving pattem of reinforcement displacement was analyzed.The results showed that geogrid displacements along the full-length obviously lagged behind the displacement at loading end,and with increase of distance away from loading end,the geogrids displacements tended to decrease nonlinearly.An increase in normal stress,compaction degree or water content caused to the decrease in geogrid displacement for the identical pullout force and the same measured points.Moreover,the farther the location of measured points is,the weaker the effect of above-mentioned factors on geogrids displacements.During the pullout tests,the main failure modes included the geogrid pulled out fully and breakup failure of geogrid,and the peak pullout forces were approximately linear with the displacement at loading end.The peak pullout forces were closely related with the normal stress,compaction degree,water content or pullout rate.To increase compaction degree or water content of backfills,which caused to enhance interface interaction of reinforcement and soil,contributed somewhat the increase of friction angle of reinforcement-soil interface made the apparent cohesion of interface to increase remarkably,and the apparent cohesion of reinforcement-soil interface reached the greater value when the water content of backfills equals to the optimum water content.The test results showed that it is necessary to strictly control the water content of the backfill soil,and allowing the reinforced structure to deform properly is conducive to playing the role of reinforcement.