Triaxial Ultra-Small Strain Measurements Using Laser Interferometry
Heymann, G
Department of Civil and Biosystems Engineering, University of Pretoria, South Africa

Clayton, C
Department of Civil and Environmental Engineering, University of Southampton, Southampton, UK

Reed, G
Department of Electronic and Electrical Engineering, University of Surrey, Guildford, UK

(Received 6 March 2003; accepted 7 April 2005)

Abstract
This paper describes a prototype device for ultra-small strain triaxial stiffness measurement, using laser-optic interferometry, and based upon the Fabry-Perot principle. The results of a test on an intact specimen of weak rock are presented, and comparisons made between measurements using this device and a submersible LVDT system. The displacement resolution of the interferometer was 0.0006 mm and the strain resolution 8×10^-7%. It is shown that the measurement uncertainty of the instrument was low compared with the magnitude of the displacements measured and in addition it was sufficiently accurate to detect the linear stress-strain behavior of a weak rock.

Keywords:
laser interferometry, local strain instrumentation, rock, small strain stiffness, triaxial test

Paper ID: GTJ10406
DOI: 10.1520/GTJ10406

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Author Heymann, G Affiliation Department of Civil and Biosystems Engineering, University of Pretoria, South Africa Author Clayton, C Affiliation Department of Civil and Environmental Engineering, University of Southampton, Southampton, UK Author Reed, G Affiliation Department of Electronic and Electrical Engineering, University of Surrey, Guildford, UK Author Heymann G, Clayton CR, Reed GT Title Triaxial Ultra-Small Strain Measurements Using Laser Interferometry Symposium , Committee on