The Bearing Capacity of Circular Footings in Sand: Comparison between Model Tests and Numerical Simulations Based on a Nonlinear Mohr Failure Envelope

Sven Krabbenhoft,Johan Clausen,Lars Damkilde

doi:10.1155/2012/947276

Abstract

This paper presents the results of a series of triaxial tests with dry sand at confining pressures varying from 1.5 kPa to 100 kPa at relative densities of 0.20, 0.59, and 0.84. The results, which are in reasonable accordance with an equation given by Bolton, show that the friction angle is strongly dependent on the stress level and on the basis of the test results, a nonlinear Mohr failure criterion has been proposed. This yield criterion has been implemented in a finite element program and an analysis of the bearing capacity of a circular shaped model foundation, diameter 100 mm, has been conducted. Comparisons have been made with results from 1g model scale tests with a foundation of similar size and a good agreement between numerical results and test results has been found.

Highlights

In conventional design of shallow foundations, earth retaining structures, slopes, and the friction angle of sand are regarded as a constant, being primarily dependent on the relative density of the material
The results, which are in reasonable accordance with an equation given by Bolton, show that the friction angle is strongly dependent on the stress level and on the basis of the test results, a nonlinear Mohr failure criterion has been proposed
The values of the friction angle according to Bolton’s equation are, in general, smaller than the test values. These differences are greater for smaller values of the relative density and the confining pressure and this tendency has been confirmed by the tests carried out by Ponce and Bell, while the tests by Fukushima and Tatsouka have shown no variation of the friction angle with confining pressures below 50 kPa

Summary

Introduction

In conventional design of shallow foundations, earth retaining structures, slopes, and the friction angle of sand are regarded as a constant, being primarily dependent on the relative density of the material. In cases where the mean effective stress is above 150 kPa the equation developed by Bolton [3] for a sand with a given mineralogy takes this dependency into account in a simple but sufficiently accurate way, but for the lower stress levels typically encountered in connection with simple model tests in a soil laboratory higher accuracy is desirable. This is due to the strong dependency of the bearing capacity factors and soil pressure coefficients on the angle of friction. As examples of this Hansen [4] and Zadroga [5] reported that the bearing capacities of model foundations found in tests are considerably higher than the ones found in calculations

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