BOTDR BASED DISTRIBUTED STRAIN TEST ON BORED PILE BURIED IN COMPLICATED GEOLOGICAL GROUND

This paper presents the principals of bored pile test using Brillouin optical time domain reflectometer (BOTDR). The formulas used to calculate the displacement, flexibility, axial force, skin friction and end-bearing resistance of piles were presented. This technique was applied to pile static load tests under complex geological conditions to detect the strains and internal forces in different types of bored piles. The test results indicate that the abnormities of the strain distribution along the piles were found at the positions of hole collapse, weak intercalation, and/or formation interface. On account of the differences of the field conditions and construction techniques, the end-bearing resistances didn't exert fully; the skin friction served as the main resistance to the loads. The piles bearing characteristics were different each other. 