Evaluation of the Interference Effect and Settlement of Closely Spaced Footings of Shallow Foundation for Two Adjacent Buildings Using FEM Analysis

Abstract

Industrialization and urbanization has run to situations where Constructions of buildings are close to each other for the reason of restricted available space that causes footings of same or adjacent structures come closer. This condition causes interference, causing the stress zones under the base of foundation to overlap, resulting in bearing capacity loss and excessive foundation settling. The problem of adjacent footings contact is extremely critical in practice. The convectional solutions for bearing capacity and soil settling under shallow foundations do not take into account the interference effects of footings. Therefore, the study aims to assess the behaviour of two closely placed footings on the two layered clay soil. The sample collected from the site for laboratory analysis following ASTM testing procedures. The result of interference of two footings in terms of bearing pressure, settlement and tilt is observed using finite element analysis. The hardening soil model used to model the foundation soil medium using the finite element analysis program plaxis 3D. The spacing between the footings, load and the depth of the footings varied in a parametric analysis. The effect of spacing with each case on the load-settlement characteristic, settlement variance, and bearing pressure investigated and the effect of water variation investigated. The results are presented in terms of non-dimensional efficiency factors, which defined as the ratio of settlement or bearing pressure of interfering footings to that of the isolated footing, in order to determine the interference effect on the performance of the adjacent building's closest footing. It is found that the interference effect on the overlapping footings decreases with increase in the spacing between the footings and gets isolated footing at greater spacing (S ≥ 5BL) and increases when the spacing between footings decreases. The maximum interference has been found at S/BL = 0.5. Similarly, when the groundwater level varies, the interference effect of overlapping footings changed. It is observed that, when water depth varies from 2.20m to 2.60m the settlement effect reduces from 33% to 20%. Thus, water level from footing depth has negative influence on the interaction of footings