Digest 2008, December 2008 1263-1279 Experimental Determination and Numerical Analysis of Vertical Stresses under Square Footings Resting on Sand † 1 M. Salih KESKİN* Mustafa LAMAN** Tarık BARAN*** ABSTRACT In this study, the vertical stress values occurring under the center line of uniformly loaded square footings were investigated experimentally and analytically. The results of the study were compared with the results obtained from the Boussinesq method. Tests were performed in a square shaped test box and a pressure transducer was used to measure the stresses. In the numerical analysis, soil was modeled using the finite element method with two dimensional axi-symmetric and three dimensional conditions as linear elastic and non- linear elasto-plastic materials and the effect of these models on the vertical stress values was investigated. Finally, a general agreement was observed between the experimental, numerical and theoretical results for the values obtained for predetermined depths of sand and the obtained results are discussed. Keywords: Sand, stress, square footing, finite elements 1. INTRODUCTION The self weight of the soil layers and applied external loads create stresses within the soil. The estimation of stress distribution in soil is quite important for the solution of a wide variety of geotechnical problems and design of foundations. The stress distribution in soil depends on the value of the applied load, the dimensions of the loaded area and the properties of the soil. Due to the complexity of the soil medium, it is quite difficult to perform realistic stress- deformation analyses [1]. The problem of stress increment in soil is generally predicted with the theory of elasticity, which assumes that stress is proportional to strain and the soil is a linearly elastic half space. In these solutions vertical stress distributions are independent from the material properties. Furthermore, the type of soil and parameters like density can not be considered and the same stress distributions are obtained for different types of soils [2]. However, the experimental and numerical studies show that, stress distribution in granular soils varies significiantly, especially depending on the soil density [3]. For that * Çukurova University, Adana, Turkey - skeskin@cu.edu.tr ∗∗ Çukurova University, Adana, Turkey - mlaman@cu.edu.tr ∗∗∗ Çukurova University, Adana, Turkey - tbaran@cu.edu.tr † Published in Teknik Dergi Vol. 19, No. 4 October 2008, pp: 4521-4538