颗粒粒径对立体格栅网–砂界面剪切特性影响

Effect of Particle Size on Shear Characteristics of Three-dimensional Geogrid–Sand Interface

传统平面格栅限制土体侧向位移的能力较弱,而立体格栅网在传统平面格栅基础上增强了横肋与土体的侧阻力作用,有助于增强加筋土结构中筋土界面的相互作用,提高加筋土结构抗变形能力和整体稳定性。为了研究网孔尺寸和颗粒粒径对立体格栅网–石英砂界面剪切特性的影响,通过3D打印技术制作不同网孔尺寸和不同增强型横肋数量的立体格栅网,利用室内大型直剪仪进行一系列单调直剪试验。试验分析了颗粒粒径、格栅网孔开口率和增强型横肋数量变化时界面的似黏聚力、摩擦角及剪切强度系数的变化规律;基于试验,建立了界面剪胀系数模型,定量分析了颗粒平均粒径和格栅网孔开口率对立体格栅网–砂界面剪胀特性的影响。结果表明:当颗粒粒径增大,界面似黏聚力最大提高了65.53%,摩擦角最大提高了7.85%,表明颗粒粒径对立体格栅网–砂界面的似黏聚力影响更明显,对摩擦角的影响较小。当竖向应力从20增大至60 kPa,不同立体格栅网–砂界面最大剪胀角降幅为38.1%~60.8%,表明界面最大剪胀角随竖向应力的增加而逐渐降低。当颗粒粒径较大、格栅网孔开口率较小时,界面的剪胀量较大;剪切强度系数随粒径的增大而增加,增幅最高可达8.76%,表明立体格栅网与粒径较大的填料之间具有更好的互锁作用。

Based on the traditional planar grid,the lateral resistance between transverse ribs and soil is enhanced by the vertical grid,which is helpful to enhance the interface interaction between reinforcement and soil,and improve the anti-deformation ability and overall stability of the reinforced soil structure.To analyze the effect of mesh size and particle size on the shear characteristics of the three-dimensional geogrid-quartz sand interface,a series of monotonic direct shear tests were carried out with three-dimensional geogrids with different mesh sizes fabricated by 3D printing technology.The effects of particle size,normal stresses,the percent open area of geogrid on the friction angle,dilatancy angle,and inter-face shear strength coefficient were analyzed.The interface dilatancy coefficient model was established,and the effects of the average particle size and the percent open area of geogrid were quantitatively analyzed on the three-dimensional geogrid-sand interface dilatancy.The results show that with the increase of particle size,the maximum apparent cohesive force increases by 65.53%and the maximum friction angle increases by 7.85%,indicating that particle size has a more obvious effect on the apparent cohesive force of geogrid-sand interface,but has little effect on the friction angle.With the increase of normal stress from 20 kPa to 60 kPa,the maximum dilatancy angle decreases by 38.1%~60.8%,respectively,indicat-ing that the maximum dilatancy angle decreases gradually with the increase of the normal stress.It is found that,as the increase of particle size,or decrease of the percent open area of geogrid,the shear dilatancy increases obviously.The shear strength coefficient is with the increasing of particle size,the increase was as high as 8.76%,indicating that the coarse particle has a better reinforcement effect with three-dimensional geogrid.