METHOD OF CALCULATING THE FOUNDATIONS IN COMPACTED PIT USING BOUNDARY ELEMENT METHOD

Abstract

The main mission of civil engineer is to ensure he reliability of the structure with maximum efficiency of time, materials and energy. In construction, everything must be provided in the design workshop - both strength and economic feasibility. Balancing on the "edge of the abyss" requires a precise mathematical apparatus. The modern mathematical apparatus of soil mechanics is based on the solutions of the theory of elasticity and the theory of limit equilibrium. In this case, the calculation of the bases is carried out from the conditions of purely elastic connection and the ultimate loads are determined without connection with deformations. Most of the elastic-plastic deformation - from the end of the elastic stage to the loss of stability is not covered by the calculation models. At the same time, the reserves of the elastic-plastic zone allow to increase the load on the foundation, provided that the subsidence of the elastic stage does not yet reach the maximum allowable value for this structure. The boundary element method (BEM) allows to solve problems of this kind.

The main disadvantage of foundations on a natural basis is the complexity of its manufacture and high material consumption. These shortcomings can be eliminated by building foundations in cavities of a predetermined shape, which are formed in the soil. These include foundations in compacted ditches, which are arranged in wells with expansion at the bottom. The soil retains its full-fledged composition, so that the work includes a side surface that receives part of the vertical load and provides significant resistance to horizontal forces.

The paper presents a method of integration of a mathematical model of behavior under load of foundations in a compacted pit with a numerical BEM. A theoretical study presents the effect of the addition of sand-gravel mixture on the bottom of the compacted pit on the bearing capacity of pyramidal piles.