Experimental Evaluation of Relative Soil–Geotextile Displacements Induced by Strip Footing Pressure on a Reinforced Foundation Bed over Soft Subgrade

This paper presents insights from small-scale model tests on a statically loaded strip footing placed on dense base sand with a single geotextile layer over a loose subgrade. The evaluation of the geotextile's benefits involved comparing the load-settlement curves obtained for the improved soil model against those observed in the unreinforced beds. The influence of inclusion on relative soil–geotextile displacements is assessed using LVDTs attached to the geotextile, digital image correlation technique, and digital microscopes. The soil–geotextile interaction mechanism was experimentally analyzed by closely observing the displacements of both the geotextile and surrounding sand. Additionally, the microscopic particle motion around the geotextile was tracked to verify the macro-behavior of the sand–geotextile interface during footing pressure increment. The results improve the understanding of sand–geotextile interaction during strip surcharge on soft subgrade reinforced foundation beds, indicating negligible relative soil–geosynthetic displacements at lower footing pressures. However, as the load increases, the relative displacements along the anchorage length become more pronounced, revealing distinct behavior at the upper and lower interfaces of the reinforcement.