CORRELATING PILE DRIVING ANALYZER (PDA) AND CASE PILE WAVE ANALYSIS PROGRAM (CAPWAP) RESULTS TO INFER SUBSURFACE SOIL VARIABILITY: A CASE STUDY ON DRIVEN SPUN PILES

Abstract

Dynamic pile testing using the Pile Driving Analyzer (PDA) combined with Case Pile Wave Analysis Program (CAPWAP) signal-matching analysis provides a rapid method for evaluating pile capacity while offering insight into subsurface behavior. This study investigates 25 driven spun piles (Ø400 mm, L = 40 m) installed in layered clay–sand stratigraphy in Dumai, Indonesia. PDA tests were performed during restrike and refined using CAPWAP analysis to obtain resistance distribution and ultimate capacity. Energy transfer efficiencies ranged from 17.24% to 26.02% (average 20.9%). Statistical evaluation indicates that energy efficiency does not strongly correlate with ultimate capacity, confirming that capacity variability is primarily governed by soil resistance rather than hammer performance. Linear regression between PDA and CAPWAP capacities shows very strong agreement (R² ≈ 0.98) with low prediction error. CAPWAP capacities varied from 139 to 218 tons. Shaft resistance contributed 85–94% of total capacity, confirming friction-dominated behavior, while toe resistance remained minor. Distribution and correlation analyses reveal a bimodal capacity pattern (140–170 tons and 190–220 tons), corresponding to localized soft clay pockets identified in CPT data. Measured capacities generally align with design predictions (180–220 tons), producing safety factors between 1.2 and 1.8. The findings demonstrate that dynamic testing, when integrated with statistical analysis and site investigation data, can function not only as a capacity verification tool but also as an indicator of subsurface heterogeneity in large-scale foundation projects.