Vertical stresses within granular materials in containments

Abstract

Containments are used to store granular materials, such as grain, sugar, flour, and pharmaceuticals. They undergo different types of loadings during their operational lifetime. There are several techniques used by the design engineers to evaluate the vertical stresses within these containments. This paper summarizes the numerical analysis of vertical normal stresses within the granular material in containments, and validation of these simulations through model tests in the laboratory. Analytical methods were developed in the past to quantify the vertical stresses in containments and trenches. As a result of arching, the vertical stresses within the granular material contained within the containments are significantly less than that expected from the overburden weight. The dependence of arching on material properties and the geometry of the containment is studied through several laboratory trials. Sand, placed at 30% relative density, was used in the laboratory model tests. Numerical simulations were carried out using fast Lagrangian analysis of continua (FLAC), a commercially available finite difference software, and the variation of vertical stress variation with depth was compared with test results, then the implications were discussed. Although an aspect ratio of 6 (height/diameter) was used in the laboratory study, extrapolation for higher aspect ratios is discussed using the FLAC simulations.