基于3D打印的立体格栅网筋土界面剪切特性研究

A three-dimensional grid network is formed by increasing the thickness of the transverse ribs on the basis of the traditional planar geogrid. The passive impedance effect generated by the enhanced transverse ribs can effectively limit the deformation of the soil. In order to study the influence of the enhanced transverse ribs in the three-dimensional grid network on the shear characteristics of the soil-reinforcement interface, based on 3D printing technology, geogrid models with 5 different transverse rib thicknesses (t = 3, 6, 9, 12, 15 mm) were fabricated. The influence of different transverse rib thicknesses and vertical stresses (σ = 20, 40, 60 kPa) on the direct shear characteristics of the three-dimensional grid network interface was analyzed through indoor large-scale direct shear tests. And on the basis of the tests, the influence of the thickness of the enhanced transverse ribs on the passive lateral resistance in the shear mode was further explored, and a theoretical calculation formula for the lateral resistance of the transverse ribs was proposed. The results show that: under different vertical stresses, the average values of the failure shear stress of the three-dimensional grid network interface (t = 6, 9, 12, 15 mm) are increased by 4.2%, 19.3%, 29.7% and 39.1% respectively compared with the planar geogrid (t = 3 mm), and the final interface dilation amounts are increased by 0.093, 0.192, 0.282 and 0.337 mm respectively; the existence of the enhanced transverse ribs increases the apparent cohesion and friction angle of the interface, and the values of the apparent cohesion and friction angle show an increasing trend with the increase of the thickness of the transverse ribs; a calculation formula for the passive lateral resistance provided by the transverse ribs to the soil particles was established, and the calculation formula for the lateral resistance was corrected by the direct shear test results, and the corrected theoretical calculation values are in good agreement with the test results.

在传统平面土工格栅基础上增加横肋厚度构成立体格栅网,其增强型横肋产生的被动阻抗作用可有效限制土体变形。为了研究立体格栅网中增强型横肋对筋土界面剪切特性的影响,基于3D打印技术,制作了5种不同横肋厚度(t=3,6,9,12,15mm)的土工格栅模型,通过室内大型直剪试验分析不同横肋厚度和竖向应力(σ=20,40,60kPa)对立体格栅网界面直剪特性的影响;并在试验基础上,进一步探讨了剪切模式下增强型横肋厚度对被动侧阻力的影响,提出横肋侧阻力的理论计算公式。结果表明:不同竖向应力下立体格栅网界面(t=6,9,12,15mm)的破坏剪应力平均值较平面土工格栅(t=3mm)分别提高了4.2%、19.3%、29.7%和39.1%,界面最终剪胀量分别增加了0.093、0.192、0.282、0.337mm;增强型横肋的存在提高了界面的似黏聚力和摩擦角,似黏聚力和摩擦角值随着横肋厚度的增加而呈现出递增趋势;建立了横肋对土颗粒提供的被动侧阻力计算公式,并通过直剪试验结果对侧阻力计算公式进行了修正,修正后的理论计算值与试验结果吻合度较好。