Feasibility and Performance Evaluation of Asphalt Concrete Cores for Rockfill Dams

This study investigated the potential use of asphalt concrete produced with locally sourced limestone and granite aggregates as an impervious core material in rockfill dams. An independent laboratory program evaluated 16 mixture conditions comprising two aggregate types, asphalt cement contents of 6% and 7%, and nominal target air-void contents of 1–4%. Marshall, hydraulic-conductivity, and consolidated-undrained triaxial tests were conducted to characterize the mixtures. The reported hydraulic conductivity ranged from 2.9549 × 10−10 to 3.8887 × 10−5 cm/s, while effective cohesion and friction angle ranged from 165.7 to 540.3 kPa and 34.07° to 55.61°, respectively. Four core-property datasets corresponding to a 2% target air-void content were evaluated using two-dimensional GeoStudio analyses under steady-state and rapid-drawdown conditions. Steady-state seepage discharge ranged from 1.967 × 10−9 to 6.7191 × 10−6 m3/s, with downstream global factors of safety of 2.209–2.215. The upstream global factor of safety at Day 7 of rapid drawdown was 2.041 for all four datasets. The granite mixture containing 7% asphalt cement and a target air-void content of 2% (Granite AC7% AV2%) was subsequently selected as a representative, rather than optimal, core-property dataset for a separate steady-state geometry comparison. Relative to the conventional clay-core baseline, a 0.50-m-thick asphalt concrete core with shell slopes of 1 V:1.5 H and 1 V:1.4 H reduced the calculated embankment volume per unit dam length by 21.11% and 24.83%, respectively, with corresponding global factors of safety of 1.655 and 1.557. A supplementary rapid-drawdown assessment of the steepest alternative yielded an upstream global factor of safety of 1.473 at Day 6, the lowest among the reported daily results. The findings provide comparative laboratory data and case-specific numerical results for preliminary assessment of asphalt concrete dam cores. Hydraulic acceptance and field-scale suitability are not established, and further experimental verification and numerical sensitivity assessments remain necessary before application.