Predicting subsidence of cohesive and granular soil layers reinforced by geosynthetic

Subsidence can result from the collapse of underground cavities. The impact of such subsidence on existing structures and infrastructures is generally dramatic. Geosynthetic reinforcement (GSY) is an attractive mitigation solution that can be used to reduce this impact. This paper focuses on the mitigation solutions over existing cavities mainly on the GSY mitigation method. A large-scale physical model (1-g) is used to study the subsidence mechanisms and to estimate the efficacy of GSY for both cohesive and granular overlying soils. The results show that the presence of GSY reduces the ground movement due to the cavity progress toward surface, even under significant overload (traffic, localised foundation, etc.). The deformation of the GSY and the scenario for ground surface movement (subsidence or sinkhole) depend on both the soil type and overload intensity. The experimental results are compared to the analytical solutions proposed to design the GSY for cohesive and granular soils. In particular, the influence of the vertical stress distribution acting on the GSY is investigated. Different geometries of stress distribution are proposed for granular soils as a function of the loading mode (self-weight or localised overload). For cohesive soils, the action of the collapsed soil on the GSY sheet is found to be well estimated by considering the effect of a simplified system composed of two well localised punctual forces. The analytical and experimental results obtained are rather similar, proving the relevance of the analytical models in predicting the behaviour of reinforced soil layers taking into consideration the real stress distribution deduced from the experimental results.