Influence of Base Reinforcement on Stress Reduction in Soft Soils

This paper investigates the effectiveness of shallow base reinforcement approaches, including Aggregate Base Course (ABC) layer with geosynthetics (geotextiles and geogrids) and lime-stabilized soil layer, in reducing stress transferred from embankments supporting pavement sections on soft soils. A combined approach of laboratory cyclic plate load tests on large-scale samples, subsequent numerical modeling using FLAC software, and field testing with stress measurements was employed. The findings revealed that geosynthetic reinforcement at the ABC layer-soft soil interface improved stress attenuation compared to unreinforced sections, particularly during post-rut repair scenarios. Back-calculated elastic modulus ratios (E1/E2) between the granular base and soft soil layers indicated a strong correlation between a stiffer base layer (higher E1) and improved stress distribution, with lime stabilization exhibiting the most pronounced stiffening effect (E1/E2 = 13). Field testing corroborated the laboratory observations, demonstrating a reduction in stress near the interface for reinforced sections. However, the observed E1/E2 ratios in the field were lower compared to the laboratory tests. Results indicated that the classical assumption of a two-layer linear elastic system led to an underestimation of stress increase in the soft soil. This underestimation is likely due to the neglect of modulus dependency on stress level and strain accumulation with an increasing number of traffic cycles.