Estudo do comportamento mecânico de solos arenosos reforçados com microgrelhas por meio de ensaios de placa

Abstract

The pursuit of improvements in soil strength and stiffness is a significant topic in geotechnical engineering. The use of geosynthetic reinforcements has proven to be an effective solution, enhancing the stability of structures and the bearing capacity of soils. These materials are applied in projects requiring greater stiffness, shear strength, and tensile resistance, such as foundations and retaining structures. Among these, microgrids perform functions of separation and reinforcement. However, as a relatively recent geosynthetic on the market, its properties as a soil reinforcement material are still underexplored in the literature, highlighting the need for further research on the subject. This research aimed to evaluate the improvement in the mechanical behavior of a foundation on natural soil by comparing it with the performance of compacted sandy soils and compacted soils reinforced with three layers of microgrids. To achieve this, three field load tests were conducted at the same location: one on natural soil, another on compacted soil, and a third on compacted soil with the inclusion of microgrids. Due to the absence of distinct physical failure in the load tests, the stiffness extrapolation method proposed by Décourt (1996; 2008) was applied to estimate the failure stress. The analyses were based on pressure versus settlement curves and parameters obtained from plate load tests, allowing a comparison of soil behavior under different conditions. The results showed an increase in bearing capacity, stiffness, vertical reaction coefficient, and elastic modulus, as well as a reduction in settlements with the use of improvement techniques. These improvements were more significant in compacted soil with microgrids. The results were also compared to failure stresses calculated using parameters from laboratory tests in previous studies with samples from the same location. The failure stresses were estimated using Terzaghi's method (1943) for saturated soils in natural, compacted, and compacted-with-microgrid conditions, and Vanapalli and Mohamed's method (2007) for unsaturated natural soil. The theoretical methods were more conservative for natural and compacted soils; however, for compacted soil with microgrids, Terzaghi's method was less conservative than the field results. This highlights the need for adjustments to better represent the conditions of tests conducted with microgrid inclusion. Furthermore, the analyses from the stiffness method in this research indicated the absence of physical failure in the respective direct load tests, a fact already supported by Décourt (2008).