Experimental evaluation of geocell reinforcement behavior using transparent soil techniques

Geocells are a growing type of geosynthetic product used in many applications, including the reinforcement of unbound granular materials for the construction of flexible pavements. Although significant research has been conducted to quantify the performance of geocell-reinforced soil masses, there is no universally accepted design method for these structures. The Mechanistic-Empirical Pavement Design Guide (MEPDG) is a solid framework on which to base a geocell design method. The resilient modulus of a material is constitutive relationship between the imposed stress state and the resilient strain. It is the relevant design parameter that should be modified in the MEPDG for the design of pavement structures using geocells. However, a more robust understanding of the behavior and mechanisms that contribute to the overall performance of geocell-reinforced materials is necessary to develop theoretically-sound model. As such, the materials and equipment necessary to conduct a thorough analysis of geocells were conceived and implemented as part of this study. This equipment is based around the transparent soil concept – transparent soils are two-part media consisting of solid particles and a saturating fluid with matching refractive indices. Fused quartz and mineral oil were selected as appropriate materials to use as a granular soil surrogate. The large-scale equipment consists of a steel-framed tank with cast acrylic sides. Many lessons were learned with regard to the use of transparent soil techniques in large-scale experiments. Preliminary results indicate the equipment is adequate to validate the results of prior geocell experiments. Additional improvements will allow for the full utilization of transparent soil capabilities and the direct observation of geocell reinforcement behavior and mechanisms in-situ.