Instrumented laterally loaded pile test using distributed fibre optic sensor

Abstract

Instrumented horizontal pile load test is widely used to evaluate lateral soil resistances/parameters and to verify design assumptions. Recent technological advancement of optical fibre sensing has led new ways in measuring the lateral load-deflection profile. The distributed sensing, namely Brillouin Optical Time Domain Analysis (BOTDA) is a novel technique of measuring strains in a spatially continuous manner. By installing distributed fibre optic strain sensing cables, continuous strain profile and deflection curve throughout the pile can be obtained. The objective of this article is to present one of the earliest deployment of BOTDA optical fibre sensors in lateral pile load test in Malaysia under offshore environment and share invaluable lessons learned from the instrumentation process. Installation method, lateral load test setup and data interpretation are also discussed. The computed lateral pile load-deflection profile was in excellent agreement with the measured pile top deflection using displacement sensors. The location of cracks detected based on continuous strain profile was also in good agreement with result of Low Strain Integrity Testing.