Tieback Retaining Wall in High Plasticity Expansive Soil

Abstract

This study evaluated the impact of moisture-induced swelling pressure on a tieback wall constructed in high plasticity expansive soil. The study was based on laboratory soil characterization, field monitored seasonal fluctuation of moisture content, and numerical simulation. Soil samples were retrieved from a construction site at the intersection of I-35 and Walters Street in San Antonio, Texas, and two boreholes were installed to monitor the moisture profile at the site. Considering the field setting, a numerical model was developed to simulate the construction and performance of a tieback wall subjected to significant lateral earth pressure due to swelling. The model further assessed the impacts of different factors on the behavior of the tieback wall, such as moisture profile, surcharge, unbonded length of the soil anchor, and wall rigidity. The study indicated that more drastic changes in soil suction profiles between construction and in-service conditions may generate lateral stresses that result in excessive wall deflections. The swelling-induced lateral stresses of the expansive soil depended significantly on the permissible lateral displacement of the retaining wall. The greater surcharge and higher rigidity led to an increase in lateral stresses. In general, this paper suggests that no simple method can predict the lateral stress due to swelling of the expansive soil and a detailed finite-element method analysis is required for designing tieback walls in expansive soils.