Design and Construction Guidelines for Deep Soil Mixing to Stabilize Expansive Soils

This paper discusses both design methodology and construction procedures for stabilizing expansive subsoils of moderate active depths, using deep soil mixing (DSM) technology/construction. These procedures were derived as a part of the research focusing on the evaluation of effectiveness of DSM technology in mitigating shrink-and-swell behaviors of expansive subsoils under actual field conditions. The design methodology formulated was based on an analytical model proposed for a DSM-treated composite section by modifying the existing heave prediction model for untreated and unsaturated expansive soils. The required area treatment ratio was determined based on the target heave magnitude for the composite section. Design charts were developed depicting estimated heave for increasing treatment area ratios and for various initial swell pressures. Based on this design methodology, DSM construction was implemented under actual field conditions at two test sites. Upon construction, both test sections were instrumented and monitored. In addition, nondestructive tests were also conducted at select time periods. Results from both instrumentation and nondestructive tests revealed that the DSM technology was effective in mitigating shrink-and-swell behaviors of expansive soils. Also, the analytical model used in the present research study has provided reasonable predictions of in situ swelling behavior of composite and untreated sections.