PERFORMANCE OF SLOPE TREATMENTS OF EARTHFILL DAMS TO PREVENT SURFICIAL FAILURES

摘要

Surficial failures of earth dams are predominantly rainfall-induced preceded by soil desiccation. Desiccation cracks accelerate the infiltration during rainfall events, which in turn increase pore water pressures and saturation of soil mass in upper layers. As a result, a drastic decrease of shear strength occurs, thereby causing surficial slope failures. Maintenance of the slopes costs millions of dollars annually. In order to mitigate these failures, a research study was undertaken by The University of Texas at Arlington (UTA) with the objective of exploring the best field stabilization method to mitigate desiccation cracks in the upper embankment soils of Joe Pool and Grapevine Dams; two dams owned, maintained, and operated by the U.S. Army Corps of Engineers (USACE), Fort Worth District (SWF). Four admixtures selected and used to treat surficial soils were 20% compost, 4% lime with 0.30% polypropylene fibers, 8% lime with 0.15% polypropylene fibers, and 8% lime. Five test sections, including four treated sections and one control section without any surface treatment were constructed at each dam site. The test sections were instrumented with moisture probes, temperature probes, and inclinometers. The sites have been monitored for a period of 2.5 years at Joe Pool Dam and 1.5 years at Grapevine Dam. Additionally, numerical modeling studies were attempted using available numerical finite element methods (FEM) based software. According to the analysis of the monitored data so far and numerical modeling studies, the 8% lime with 0.15% fibers has been found to be the most effective admixture treatment at both sites to prevent desiccation cracking and surficial failures.