预应变土工格栅与砂垫层界面特性试验研究

Experimental Investigation on Interface Characteristics Between Pre-Strained Geogrid and Sand Cushion

采用拉拔试验研究了预应变土工格栅与砂垫层的界面特性,通过对比分析试验结果,对法向应力、垫层厚度和预应变初值对筋土界面特性的影响进行了研究,结果显示:砂垫层厚度为5 cm时,低应力条件下预应变土工格栅与普通格栅的拉拔阻力峰值相差不大,随着法向应力的增大,预应变土工格栅的抗拔性逐渐优于普通格栅,而应变软化现象也愈明显;法向应力为50 kPa时,垫层厚度的增大对格栅抗拔性有一定提高,当厚度达到15 cm后提高效果明显减弱,且高预应变水平的土工格栅随着垫层厚度的增大会出现应变软化现象。最后通过数据拟合得到了界面抗剪强度包络线,预应变加筋法能显著提高格栅与砂垫层界面似摩擦系数,减小界面似粘聚力,可为预应变加筋法的推广提供参考。

The interface characteristics between pre-strained geogrid and sand cushion were studied through a serious of pullout tests.The experimental program was divided into two parts,the influence factors,such as,normal stresses,cushion thickness and initial strain,on the interface characteristics of pre-strained reinforcement were investigated by comparing the results of the comparative analysis.Under the low normal stress condition,the results showed that the pre-strained geogrid and the conventional geogrid have little differences on the peak value of tension resistance when the thickness of sand cushion is 5 cm.The tensile stress of the pre-strained geogrid is much higher than that of the conventional geogrid and the strain softening phenomenon is becoming obvious with the increase of the normal stress.When the normal stress is 50 kPa,the increase of the thickness of the sand cushion has an improvement to the tension resistance.When the thickness reaches 15 cm,the effect is obviously reduced,and the strain softening will occur on the geogrid with a high pre-strain level.Finally,the envelope of the shear strength of the interface is obtained by fitting the experimental data.It is concluded that the pre-strained reinforcement can significantly increase the coefficient of quasi friction between the geogrid and the sand cushion and reduce the quasi interface cohesive force at the same time and provides theoretical basis for the popularization of pre-strained reinforcement method.