Interpretations of Instrumented Bored Piles in Johor Bahru Old Alluvium Formation

Abstract

In evaluating pile foundation performance, static load tests (SLT) play a critical role, as they offer a direct and reliable measure of how a pile responds under both working and ultimate load conditions. Traditionally, these tests focus on pile head load–displacement relationships. However, when piles are instrumented with vibrating-wire strain gauges (VWSG) and extensometers, the amount and quality of information obtained increase substantially. Such instrumentation allows designers and engineers to observe the mobilisation of shaft friction at different depths, distinguish the contribution of end-bearing resistance, monitor toe movement, as well as quantify elastic shortening along the pile shaft. Most importantly, it provides a clear understanding of how shaft friction and end-bearing components develop progressively with increasing pile displacement, forming a complete picture of the load transfer mechanism. Therefore, detailed interpretations of static load test results from instrumented bored piles constructed within the Johor Bahru Old Alluvium formation are carried out in this study. Through careful evaluation of strain distributions and load transfer profiles, ultimate shaft friction values of 6.35N for layers with SPT N-value ≤ 15, and 2.35N for layers with SPT N-value > 15, are established. These correlations offer meaningful insight into the behaviour of Old Alluvium materials under pile loading and provide practical parameters for use in design. The findings contribute directly to improved optimisation of pile lengths, particularly for projects with varying pile diameters and embedment depths in similar geological settings. By adopting design values grounded in instrumented test data, engineers may prevent unnecessary conservatism, reduce material usage, and achieve substantial savings in foundation construction costs while ensuring safety and performance.