The interaction behavior of geogrid reinforced soil is significantly influenced by the direction of force transmission between geogrid and soil. Moreover, a distinction is to be made between geogrids with a directly applied tensile force and geogrids which are indirectly loaded via the surrounding soil. In particular, the latter case of indirect geogrid activation, that occurs e.g. in base layers of embankments or foundation pads, involves a fundamental need for research with regard to forces and deformations.
This paper gives an overview of the existing concepts of interaction and classifies them into a global and a local approach, distinguishing between direct and indirect geogrid activation. Furthermore, a new test device for the investigation of the local interaction mechanisms during indirect geogrid activation is presented. For this purpose, transparent geogrid reinforced specimens are biaxially loaded, whereby an area-wide and undisturbed insight into the geogrid-soil interface is enabled. The transparent soil is created as a two-phase medium consisting of crushed quartz glass and a white oil with a corresponding refractive index. First experimental results show the displacement fields of geogrid and surrounding transparent soil, whereby the “pushout”, “pullout” and “interlocking” mechanisms can be identified. The present investigations serve as a basis for soil-mechanical approaches in order to describe the interaction mechanisms and to create an interaction model for the case of indirect geogrid activation.
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