Investigation of the cause of failure of building structures in Damaturu, Northeastern Nigeria, using electrical resistivity method

Abstract

In this study, building failures were investigated in Damaturu metropolis, using Electrical resistivity method which involves, both Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT). The study reveal that the area is composed of five geologic layers, which are the topsoil, clay, sand, sandy-clay, and sand. The topsoil thickness ranged from 0.7 to 1.9 m and has resistivity values which ranged from 127.6 to 171.5 Ωm. The second layer which is a clay formation has a thickness which ranged from 6.9 to 12.6 m. The topsoil is thin in most parts of the study area and it is mostly excavated during the building process for foundation laying and thereby leading to a situation where the foundation of the buildings are footed on the second layer which is a clay formation. The study reveal that the foundation of most buildings in the study area are underlain by clay. Clay soils often swell during rainy season and shrink during the dry season. Considering the appreciable thickness of clay in the study area, the swelling and shrinking behavior of clay is responsible for the failure and collapse of buildings in the study area. The resultant swelling and shrinkage of the clay under the foundation, subjects the buildings to shear stress which culminate in cracking of walls and deformation of the buildings. The study revealed that the materials underlying the building foundations in the study area are incompetent and they deserved to be compensated during building construction by using appropriate foundation types or by engineering reinforcement, using concretes to enhance the load bearing capacity of proposed building sites in the study area.