The use of fibre optic instrumentation to monitor the O- Cell load test on a single working pile in London

A large diameter pile was constructed in London to support 18 MN of structural load. The pile was designed to rely heavily on the base bearing capacity which is founded in the underlying Thanet Sand material. Base grouting was also specified and the pile was designed to be tested by the Ostcrberg load cell (O-Cell) up to the working capacity. The Osterberg load cell will remain within the pile after the testing, and such an approach requires additional consideration compared to the more usual use of an O-Cell within a sacrificial pile. The pile was instrumented by both conventional Vibrating Wire Strain Gauge(VWSG) and novel Optical Fibre Sensor(OFS) during the pile base grouting and the O-Cell pile test. The distributed temperature measurement during the concrete hydration period was also captured. This paper discusses the results obtained from both VWSG and OFS during the O-Cell test, and provides information about the pile bearing capacity and recommendations with regard to the use of O-Cell within working piles