Avaliação dos métodos de cálculo da capacidade de carga de sapatas assentes sobre solo melhorado com cimento.

Abstract

Shallow foundations are widely used as a foundation solution for small and medium sized works in engineering, however, their use depends directly on the quality of the soil on which it will be laid. Once the soil does not present adequate resistance, more expensive solutions, such as deep foundations, are required. In order to reduce costs in the face of this problem, the improvement of soil characteristics with cement, discussed in this paper, presents itself as a possible viable and affordable solution, however, it is necessary to know the gain in compressive strength achieved with the soil improvement with cement. For this study, the natural cohesive frictional soil from the experimental field was treated with a mixture of Osório sand with a 7% content of Portland cement CP V-ARI, used in the proof loading tests taken from the literature, which were tested with a 30 cm diameter plate for three different layers, with a constant thickness of 30 cm, and variable width of 45, 60 and 90 cm, in which all showed significant gains in load capacity of the soil, thus proving to be a viable alternative for use in the foundations of footings, so it is necessary methods that reliably assess the load capacity of this new soil, so that its application is safe and effective. Therefore, the present study evaluated the best method to calculate the bearing capacity of a soil improved with cement. The methods Myerhof, Thomé, Meyerhof and Hanna and Brinch-Hansen were evaluated. Thus, it was possible to realize that the Meyerhof method overestimated the values of bearing capacity, with a tendency for the values to move away from the higher the treated layer when compared to the proof load tests, as in the 90 cm layer, reaching 520.75% of the test value, thus presenting itself as inadequate for this purpose. The Thomé method proved ineffective because it did not consider the effect of the change in the treated width, presenting fixed values for the three layers. The Meyerhof and Hanna method overestimated by about 300% the values for the three layers studied, also proving ineffective in the analysis for soil improved with cement. The Brinch-Hansen method, on the other hand, showed the best results, reaching a difference of 16.04% for the 45 cm layer. However, it showed a tendency to deviate from the test values the larger the treated layer, reaching a difference of 102.78% for the 90 cm layer. Thus the results achieved by the methods mentioned above showed to be ineffective to evaluate the load capacity of soils improved with cement, reinforcing the need for further studies in this area in order to establish a safe and effective method, since the advantages that this solution can bring in economic terms.