TABLE OF CONTENTS Expansive soils are a worldwide problem, causing extensive damage to civil engineering structures. Jones and Holtz estimated in 1973 that the annual cost of damage in the United States due to expansive soil movement was $2.3 billion (Jones and Holtz, 1973). A more up-to-date figure is about $9 billion in damages annually to buildings, roads, airports, pipelines, and other facilities (Jones and Jones, 1987).
Chapter 8 discussed the consolidation of clay, which is basically the compression of soft clays that have a high water content. Expansive clays are different in that the near-surface clay often varies in density and moisture condition from the wet season to the dry season. For example, near- or at- surface clays often dry out during periods of drought but then expand during the rainy season or when they get water from irrigation or leaky pipes.
There are many factors that govern the expansion behavior of soil. The primary factors are a change in water content and the amount and type of clay size particles in the soil. Other important factors affecting the expansion behavior include the type of soil (natural or fill), condition of the soil in terms of dry density and moisture content, magnitude of the surcharge pressure, and amount of nonexpansive material such as gravel or cobble size particles (Ladd and Lambe, 1961; Kassiff and Baker, 1971; Chen, 1988; Day, 1991b, 1992a). These main factors are individually discussed below:
Change in Water Content. An important factor for expansive soils is...
