双向和三向土工格栅筋土界面特性对比试验研究

Comparative Experimental Investigation of Geogrid-soil Interface Behavior of Biaxial and Triaxial Geogrid

以双向土工格栅SS20和三向土工格栅TX160为对象,通过开展室内直剪试验和拉拔试验,并对拉拔试验中土工格栅试样4个断面的位移进行量测,研究了SS20和TX160的变形及筋土界面特性,对比分析了SS20和TX160方案的筋土界面剪应力发挥过程和作用机制、土工格栅变形、筋土界面剪胀(缩)特性和强度参数,同时探讨了试验方法对试验结果的影响.研究结果表明:拉拔试验中,TX160的筋土相互作用集中在拉拔端附近,而SS20沿试样全长均能较好地发挥其作用;相比于SS20,增大竖向压力可以更好地增强TX160与周围填料颗粒的相互作用;SS20方案的峰值摩擦角和残余摩擦角均大于TX160方案,但黏聚力刚好相反;竖向压力对直剪试验和拉拔试验所得筋土界面强度参数均有明显影响,实际工程应用中应根据土工格栅的实际应力状态确定合理的试验竖向压力.

Laboratory direct shear test and pullout test were conducted focusing on biaxial geogrid (SS20) and triaxial geogrid(TX160) to investigate the deformation and geogrid-soil interface behavior.The displacements of geogrid specimens were recorded at 4 sections in the pullout test.The development of geogrid-soil interface shear stress,geogrid deformation,shear dilatancy/shrinkage behavior and interface parameters were analyzed,and the effect of test methods on the testing results was also investigated.The results show that the interaction between the geogrid and soil of TX160 concentrates at the vicinity of pullout end.However,this interaction is well developed along the full length of SS20 specimens.Meanwhile,this interaction of TX160 can be better enhanced with the increase of vertical stress compared with that of SS20.Both the peak and residual friction angles of SS20 case are greater than that of TX160 case,while the cohesion is just opposite.The vertical stress has obvious effect on the geogrid-soil interface strength parameters obtained from both the direct shear test and pullout test.Thus,the vertical stress adopted in the test should be determined based on the actual stress status of the geogrid for engineering application.