A Study of Injection of Chemical Agents in an Expansive Clay

Expansive clays exhibit high potential for volume change because of changes in soil moisture. It is estimated that the annual cost of damage to facilities built on expansive clay in the United States exceeds $9 billion. Because of the physico-chemical nature of expansive clay behavior, the use of chemical agents to improve their behavior is common. The research reported involved development of a viable method to simulate injection of chemical agents into soils and evaluation of the results. The agents included in this study were lime, a potassium based agent and a group of what are called ionic agents. The clay utilized was weathered from the Eagle Ford Shale formation in north central Texas. An injection treated layer of the clay, using one of the differing chemical agents, was placed between a relatively wet layer and relatively dry layer of untreated clay, to test each chemical's affects on moisture movements. The sealed cylinders were allowed to have what moisture movements during a fifteen week period. The cylinders were opened and the soil layers tested for water content, dry unit weight, soil suction, and swell potential. Cylinders of untreated clay, constructed in the same way, but not injected were also analyzed. The injection process developed is believed to have simulated field injections well. The results of moisture movement, soil suction, and swelling potential provided insight into how these chemical agents can affect moisture movements and soil behavior when injected in this clay.