Climate‐Controlled Soil Design Parameters for Mat Foundations

Abstract

Mat foundation design requires an analysis of the mat when subjected to unsupported regions due to swelling or shrinkage of expansive soils. A study was conducted to investigate simple rational methods for calculating the active zone depth (z) and from it the edge moisture penetration distance $\left(L_m\right)$ in expansive soils. Analysis of soil moisture diffusion assuming a periodic variation in surface‐soil suction indicated that z can be a function of the maximum suction change imposed, minimum suction change considered significant, climate frequency, and field diffusion coefficient. The $L_m$ may be given by $z-D$ where D is the depth of the foundation or perimeter stiffening beam below ground surface. Data required to evaluate z and $L_m$ were obtained from field observations made during an 18‐month study on airport pavements on expansive soils. These climatic parameters may also be used in design of mat foundations supporting structures.