筋土界面变形破坏模式细观试验研究

利用自制的模型试验设备,在平潭标准砂中对玻纤网布和土工格栅进行了一系列拉拔试验,应用数字照相变形量测技术,从细观角度研究土工合成材料(片状的和格栅状的)接触界面的变形模式,得出接触面的形式和厚度,还研究了土工格栅横肋作用下土体的破坏模式。接触界面区域在传统意义上并不被认为是剪切带,本文模型试验的结果表明二者在本质上是一致的。在土工格栅拉拔试验中,土工格栅的位移逐步从前部向后部发挥,出现上下两条接触面区域,其厚度在密砂和松砂拉拔试验中相当于5倍和7.5倍平均颗粒直径;在玻纤网布拉拔试验中,只出现一条接触面,其厚度为7.5倍平均颗粒直径;随着位移的增加,格栅横肋在土中的最大剪应变集中区域呈“x”形,但并不对称。本文揭示了加筋土的宏细观力学机理,研究内容、方法和主要结论可为类似的研究提供参考,并从细观机理上为接触界面的研究提供新的认识和理解。

Mesoscopic Study of the Interface Failure Modes between Soil and Geo-Synthetics

With self-designed model-test apparatus, a series of pull-out tests were conducted on Pingtan standard sand. In use of the digital photogrammetry for deformation measurement (DPDM), the deformation and the failure mode of interface between synthetic reinforcement (flake & grid) and soil were investigated, and the form and thickness of the interface were obtained. Meanwhile, a study has been done on the deformation and the failure modes of soil affected by the transverse rib of the geo-grid. Traditionally, the interface shear zones between particulate materials and geosynthetics continuum elements have not been considered as shear bands, however, the results of presented meso-scale experiment have shown that they are indeed the same in essence. In the pull-out tests of the geogrid, there were two interfaces, whose thickness in compact sand and loose sand are five times and 7.5 times the average sand particle diameter respectively; in the pull-out tests of the fiberglass mesh, there was only one interface, whose thickness is 7.5 times the average sand particle diameter; as the displacement increases, the shear strain intense region of the transverse rib of the geogrid in soil is of the X shape but asymmetrical. This paper revealed the meso-mechanism of reinforced soil and provided some helps to similar investigation in content, method and the main conclusion, as well as some new ideas for the study of the interface between reinforcement (flake & grid) and soil in its meso-mechanism.