粒孔比对筋-土界面循环剪切特性的影响

加筋土结构的动力性能对公路、铁路、边坡和挡墙等实际工程具有重要意义，因此研究筋-土界面的动力剪切特性具有重要意义。试验选用填料为4种不同粒径范围的粗颗粒土：0.5~1.18 mm，1.18~2.36 mm，2.36~4.75 mm，4.75~8 mm，一种方形网孔的土工格栅，土工格栅的网孔尺寸为30 mm×30 mm，在剪切速率分别为0.25，1，2，5 mm·min^-1，相对密实度分别为22%、55%、75%的条件下，研究填料平均粒径与土工格栅网孔尺寸的比值（粒孔比）对土工格栅-粗粒土界面循环剪切特性的影响。研究结果表明：当粒孔比从0.04增大到0.20时，土工格栅-粗粒土界面的剪应力峰值先增大后减小，粒孔比为0.07时，土工格栅-粗粒土界面的剪应力峰值最大；粒孔比分别为0.04，0.07，0.11，0.20时，土样的最终剪缩量分别为2.547，2.583，3.150，5.021 mm，表明随着粒孔比的增大，土样的最终剪缩量增大；同一循环次数下，粒孔比为0.07时，土工格栅-粗粒土界面的剪切刚度最大；粒孔比为0.20时，土工格栅-粗粒土界面的阻尼比最大；同一循环次数下，当剪切速率从0.25 mm·min^-1增大到5 mm·min^-1时，土工格栅-粗粒土界面的剪应力峰值先增大后减小；随着剪切速率的增大，土工格栅-粗粒土试样的最终剪缩量增大；相对密实度分别为22%、55%、75%的条件下，粒孔比为0.07时，剪应力峰值均达到最大值，分别为66.63，76.79，79.17 kPa。

Influence of Aperture Ratio on Cyclic Shear Behavior of Geogrid-soil Interface

The dynamic properties of reinforced soil structure are important for practical engineering such as construction of highways, railways, slope and retaining walls. Hence, it is necessary to study the dynamic shear characteristics of geogrid-soil interface. Four types of sand, with particle diameters ranging between 0.5-1.18 mm, 1.18-2.36 mm, 2.36-4.75 mm, and 4.75-8 mm, and geogrids with square aperture of size 30 mm×30 mm were tested to study the effect of aperture ratio, i.e., the ratio of the average sand particle size to geogrid aperture size on the dynamic shear behavior of geogrid-coarse soil interface using a large-scale direct shear device. The shear rates obtained are 0.25, 1, 2, and 5 mm·min^-1, respectively, and the corresponding soil densities are 22%, 55%, and 75%, respectively. Experimental studies reveal that when the aperture ratio increases from 0.04 to 0.20, the peak shear stress of interface first increases and then decreases, with the largest peak shear stress of interface occurring at an aperture ratio of 0.07. For aperture ratios of 0.04, 0.07, 0.11, and 0.20, the ultimate vertical displacement of interface are 2.547, 2.583, 3.150, and 5.021 mm, respectively. Thus, the ultimate vertical displacement increases with an increase in the aperture ratio. Under the same cyclic times, the largest shear stiffness of interface and damping ratio of interface occur for aperture ratios of 0.07 and 0.20, respectively. with the increasing of the shear rate from 0.25 mm·min^-1 to 5 mm·min^-1, the peak shear stress of interface first increases and then decreases, while the ultimate vertical displacement increases continuously. The peak shear stress of interface is the largest for an aperture ratio of 0.07. For soil densities of 22%, 55%, and 75%, the peak shear stress of interface are 66.63, 76.79, and 79.17 kPa, respectively.