Finite expression and models for footing resistance in substations

Footing resistance in a substation is affected by the limited crushed rock layer usually spread on the surface of the soil. A finite expression for calculation of the footing resistance is given. Two simple and fairly accurate models for determining the footing resistance are developed. The results obtained from the finite expression and the models are compared with the accurate results obtained from the infinite summation series. A method to calculate the decrease in footing resistance because of the accumulation of dirt at the lower portion of the crushed rock layer in old substations is also presented