Effect of Glass Fiber Reinforcement on Bearing Capacity and Settlement of Foundations on Soft Clay

In today’s rapidly developing infrastructure sector, which includes the construction of mega structures such as express highways, railways, tunnels, bridges, and tall buildings worldwide, finding suitable ground for these civil engineering projects poses a significant challenge for geotechnical engineers. Fortunately, several ground improvement techniques exist to strengthen weak and soft soils, tailored to the specific requirements of each application. In recent times, the use of Fiber-Reinforced Polymer (FRP) materials has gained popularity due to their multifunctionality, particularly in reinforcing concrete sections. This research delves into innovative approaches by employing FRP bars to enhance the bearing capacity and stiffness of soft clay soils. Specifically, two different polymer materials are investigated: uniaxial geogrid (an elastic–plastic material) and FRP (an elastic material). These materials aim to improve the bearing capacity of soft soil and enhance stability under loaded square footings. To explore their effectiveness, a model test was conducted using a square footing resting on soft clay. The study examined the impact of embedded FRB layers on controlling soft clay settlement and enhancing shear strength. The experimental model results were compared with analytical solutions obtained using the finite element program ABAQUS, revealing good agreement between computed and measured data. Further understanding of FRP—soil interaction outside the calibrated model is required to bridge the gap of the knowledge. Accordingly, a set of parametric studies were carried out using the calibrated numerical model. These studies investigated various parameters affecting the interaction mechanism between the soil and geogrid or FRP. Comparing reinforced and unreinforced cases, it was evident that using FRB is more effective than geogrid in improving the soft clay properties particularly in terms of settlement reduction and increased bearing capacity. Employing the FRP as reinforcement material significantly reduces soft clay settlement by approximately 48% while increasing its bearing capacity by about 93%. However, employing the geogrid reduces the settlement by about 30% of that developed unreinforced soil, while the bearing capacity of original soil increases by about 50%. Also, the efficiency of FRB layers is clear by adopting it at depth not less than 2.2B where, the first FRP net located at distance U = 0.7B under the footing. Also, the length FRB should be not less than 2B to be effective in reducing the consolidation settlement of the soft clay. Moreover, utilizing sand replacement with FRP layers proves effective in further reducing settlement and improving of bearing capacity of soft clay by about 90% and 130% respectively of that calculated in the unreinforced case.