Pengaruh Kepadatan Zona Inti Bendungan Karian Terhadap Tekanan Air Pori pada Tahap Impounding

Abstract

This study analyzes the relationship between core zone density and pore water pressure development during the initial impoundment phase of the Karian Reservoir in Lebak Regency, Banten. This zoned embankment dam features a vertical clay core compacted using a wet compaction method from elevations +6.90 m to +28.0 m, followed by dry compaction for the overlying layers up to the core crest. Field and laboratory quality control data (September 2018–February 2022) were evaluated alongside piezometer data from four elevations (−8 m, 10 m, 30 m, 45 m) recorded during the impoundment period (October 2023–May 2025). The core material exhibited a water content of 44.0–60.0%, a dry unit weight of 1.025–1.178 t/m³, and a permeability coefficient of 6.05 × 10⁻⁹–3.11 × 10⁻⁹ m/s, demonstrating strong inter-parameter correlations. Analyses of excess pore water pressure (∆U) and the pore pressure ratio (Ru) revealed development patterns consistent with theoretical predictions; Ru values below 0.5 indicated stable conditions free from hydraulic instability. Negative pore pressures at upper elevations (−294 to −441 kPa) indicated incomplete saturation, while an effective filter and drainage system accelerated pore pressure dissipation and maintained the dam's integrity. The study confirms that controlling water content and density through wet compaction is effective in maintaining pore pressure stability within a tropical climate characterized by high rainfall.