The influence of post-compaction saturation on the resilient behavior of a lateritic soil used in road subgrade
DOI:
https://doi.org/10.6008/CBPC2179-6858.2021.002.0025Keywords:
Soils, Subgrade, Resilient modulus, Post-compaction saturationAbstract
Aiming to improve the performance of Brazilian pavements regarding fatigue cracking and permanent deformation defects, a new dimensioning methodology is being proposed, the National Dimensioning Method (MeDiNa), which aims to replace the empirical approach applied to highways by the DNER method so far. MeDiNa promotes a mechanistic analysis and requires precise information on the properties of each material used in the pavement layers, including the subgrade resilient modulus (MR), an influential property on the structure deformability and fatigue life, whose study is fundamental for the success of highway projects. To add knowledge regarding soils MR, the present research seeks to evaluate the influence of post-compaction saturation on the resilient behavior of a soil used in road subgrade of Rio Grande do Sul. For this purpose, a clay soil with lateritic behavior was selected to be the object of this study. After compaction under optimal conditions, repeated load triaxial tests were performed to determine the MR in samples with the optimum compaction moisture and soaked samples, which were immersed in water for a period of four days. The research found a drastic decrease in the resilient capacities of this material, reaching a reduction of up to 80.5% caused by the period of immersion in water. The simulations with the MeDiNa software, in a typical pavement structure, comparing the fatigue life, with subgrade MR in optimum moisture content and soaked showed that such decrease in the subgrade MR, due to lack or inefficiency of drainage, leads to early cracking in the pavement, with an estimated reduction of 20% in the fatigue life under the simulated conditions. Relating this performance decrease to monetary parameters, the inability to support design loads and reduced durability resulted in 29% increase of the construction cost, in terms of price/km.Neq.
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