In this article, the authors analyzed the influence of the loading time, magnitude, and loading approach (loading device type and weight) on the vertical displacements registered in the pavement subgrade static plate load test. The three-dimensional finite element method computational model was developed. Conducted numerical analyses were verified in field tests. Three layer systems of different stiffnesses were examined. The visco-plastic behavior of the subgrade was taken into account in the numerical computations as well as the reach and superposition of the deflection (displacements) basins at different loading configurations (loading device type and weight). Essential discrepancies in both the field measurement results and computation results were observed for different loading times and approaches at the same loading level of the plate. The ambiguity of the pavement subgrade static plate load test results interpretation due to different load-time test conditions was explained.
This article analyzes the results of testing the subgrade and the lower layers of the pavement structure with the light weight deflectometer at a load of 0.1 and 0.15 MPa. It is shown that, with layer systems with an equivalent layer modulus lower than 80 MPa, significant nonlinear phenomena occur at a load of 0.15 MPa. In this situation, the identification of a reliable replacement module, a commonly used test method, at a load of 0.1 MPa, is not appropriate—it significantly overestimates the value of the modules (even by 34%), which in turn translates into a significant overestimation of the fatigue life of the structure. In a situation where intensive exploitation of the lower layers of the pavement structure is planned before the final layer arrangement is made, it is required to apply test loads corresponding to the stress conditions occurring in these layers of the structure. Such a situation takes place under the influence of technological (construction) or temporary traffic (substitute, e.g., by-pass) during construction. In order to verify the above assumptions, numerical calculations (FEM) were carried out in the elastic model for layered structures with replacement modules determined in field tests. It was found that, especially in the case of low-bearing layer systems, it is necessary to use correction factors for modules determined with a dynamic plate at a load of 0.1 MPa. Taking into account the corrected values of the modules will allow to correctly determine the change in the durability of layers at the construction stage and in the subsequent operation of the final pavement structure.
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