Investigation of the dynamic strain responses of sandstone using multichannel fiber-optic sensor arrays

Abstract

In the process of rock mechanical experiments, strain-response measurement is a most fundamental and most essential procedure for geomechanical researchers. The main objective of this paper is to point out the feasibility and the superiority of the application of a novel multichannel fiber Bragg grating (FBG) sensor arrays for dynamic strain-response measurements of cylindrical specimen subjected to uniaxial compression. The principle, design, and embedment of multichannel FBG sensors used in the experiment are briefly described. To fully monitor the strain history of the sandstone cylinder in uniaxial compression, six circumferential FBG sensors, four lateral FBG sensors, linear variable differential transformers (LVDT) built-in machine have been utilized for spatially monitoring small radial and axial strains along the height of the specimen, respectively. The experimental results indicate that the proposed FBG sensors can successfully provide a full-field view of the surface strains, as well as detect the potential crack locations within the specimen, and strains measured by multichannel FBG sensors are in good agreement with the results of LVDT, especially in the axial strains. Hence, it could be inferred that multichannel FBG sensor arrays are capable of measuring dynamic strain responses of sandstone specimen in multistage compression, which would greatly strengthen experimental basis for further application and theoretic research of in-situ field monitoring.