PERFORMANCE-BASED OPTIMIZATION OF PILE SOCKET DESIGN IN SRI LANKAN METAMORPHIC BEDROCK
A.U.V.B. Bulathsinhala1* and U.G.A. Puswewala2
1Institute of Technology University of Moratuwa, Homagama, Sri Lanka, 2Sri Lanka Institute of Information Technology, Malabe, Sri Lanka
Session: Technical Session A
Abstract
Pile socketing into bedrock is a common foundation technique in Sri Lanka. However, current design practices remain excessively conservative, leading to unnecessary construction costs. Despite the prevalence of competent metamorphic rocks, local designers continue to apply methods developed for sedimentary formations, significantly underestimating the available skin friction capacity. Field load tests have demonstrated that actual mobilized skin friction values frequently exceed design predictions by up to three times, as per local design guidelines. This conservatism stems from the use of high safety factors (often 3.0 or more) and outdated assumptions regarding rock-concrete interface behaviour. This study investigates the optimization of pile socket design by critically evaluating current practices and proposing data-driven improvements. Through an extensive review of case studies and pile load test results across Sri Lanka, the research highlights discrepancies between theoretical predictions and actual field performance. The analysis focuses on key parameters influencing socket capacity, including rock quality, socket roughness, and construction techniques specific to metamorphic formations. The findings reveal that existing design approaches fail to account for the superior mechanical properties of Sri Lanka’s crystalline bedrock, resulting in over-designed and costly foundations. This study develops refined design recommendations that reduce reliance on excessive safety margins while ensuring structural reliability. The proposed optimization framework has the potential to achieve significant cost savings of 50% in foundation construction without compromising safety. This research provides a foundation for updating national design standards and promotes more efficient use of Sri Lanka’s favourable geotechnical conditions. The outcomes will benefit practicing engineers, contractors, and clients by enabling more economical, yet safe pile designs. Future studies should expand the database of load test results to further validate and refine the proposed methodology.
Keywords: pile socket design, skin friction, metamorphic rocks, foundation optimization, load test analysis
DOI: 10.64752/GCNL4751