Estudo experimental, numérico e analítico de colunas granulares encamisadas

Abstract

Structures on soft soil deposits are a challenge for geotechnical engineering due to their low bearing capacity and high compressibility. Stability with granular encased columns is one of the most used solutions, however, when applied to extremely soft soils, there may be no lateral confinement. For this, a geosynthetic casing is used, which promotes additional confinement, leading to the mobilization of greater shear strength. Thus, it’s important to deepen the study on the action of lateral loading, since the request can occur at the tip of the embankments and in the movement of soil during earthquakes. Thus, the objective of this document is to analyze the behavior of granular encased columns behavior subjected to shear, approaching the methodology of Raithel and Renne (2000), performing direct shear tests in miniaturized GEC's, and numerical modeling representative of the behavior observed in the reduced model. (1g type). In the field, the use of granular encased columns takes place in soft soil, however, for the simulation, sandy was used to fill the column and the area surrounding it. The material was rained with relative densities of 40% and 100%. Direct shear strength tests were carried out with a granular encased columns with LDPE plastic canvas (stiffness equal to 20, 40, 80 and 160 kN/m) and plastic film (1.34 and 3.46 kN/m), seeking to obtain rigidities equivalent to those used in practice. A group analysis was also performed with LDPE plastic tarpaulin lining with 1, 2, 4 and 9 columns. Numerical analyses were carried out using the PLAXIS 3D software in order to verify the occurrence of liner rotation during shear and the deformation of the geosynthetic associated with the post-peak condition. The comparison of the tests with the metodology of Raithel and Henne (2000) was carried out with the results obtained with the lining in plastic film. The results showed that the addition of columns and the stiffness of the casing increases the shear strength of the set. The calculation method for increased friction angle led to satisfactory values. The calculation method for increased cohesion had a small correspondence with the values obtained in the tests. The numerical modelling has shown that GEC's do not rotate significantly at the base of the shear box and its fixation is not necessary