Graduate Defense: Ajay Kumar Reddy Pisati

Thesis Information

Title: Maximizing the Performance of Geocell Reinforced Pavement Bases with High-Fines Content Soils through MICP Treatments

Program: Master of Science in Civil Engineering

Advisor: Dr. Bhaskar Chittoori, Civil Engineering

Committee Members: Dr. Nick Hudyma (Co-Chair), Civil Engineering; and Michael Dickey, Civil Engineering

Abstract

Crushed stone and gravel have long been favored for their stability and interlocking properties in Geocell reinforced base course layers of flexible pavement structures. However, their drawbacks, such as depleting reserves, escalating permit costs, environmental compliance, and extensive quarrying impacts, have led researchers to seek alternative options like recycled and on-site materials. Within this framework, utilizing native soil emerges as a promising solution to tackle these challenges. Nevertheless, the grading specifications impose limitations on the fines content allowed in base courses, as determined by the No. 200 sieve. However, the grading specifications pose restrictions on the permissible fines content in Geocell reinforced base courses, as defined by the No. 200 sieve. Extensive research has consistently demonstrated that exceeding the established fines content limit significantly undermines the performance of the soil, particularly in terms of its strength characteristics. This poses a significant challenge when it comes to incorporating native soil into base courses. The primary objective of this study was to enhance the performance of geocell-reinforced pavement bases utilizing soils with high fines content as a substitute for traditional crushed stone and gravel. The focus was on evaluating the effectiveness of combining Geocells and Microbial Induced Calcite Precipitation (MICP) treatments to achieve this objective. The soil characteristics were evaluated through three laboratory tests: the California Bearing Ratio test, the Calcium Carbonate Content test, and the Free Swell Index test. Although the results indicate a decline in performance as fines content increases, this approach widens the possibilities of allowing relatively higher fines content compared to current specifications.