A New Three-Dimensional Pressure Transducer for Measuring Soft Rock Stress

Commonly used methods of measuring rock stress, including hydraulic and borehole relief methods, are difficult to apply in deep soft rock masses. This study proposes a new method to measure stress in soft rock by taking advantage of the strong rheological behavior of soft rock masses. Rock stresses can be gradually measured over time by embedding pressure transducers into soft rock masses; this can be accomplished with a newly developed vibrating-wire pressure transducer that can monitor three orthogonal normal stresses. Based on the elastic theory, this study derives the relationship between applied pressures and frequency changes of the vibrating wire. Uniaxial and triaxial calibration tests were performed using a rock mechanical testing system to investigate the repeatability, linearity, and interference characteristics of the new transducer. The performance of the transducer was also verified in a model test using a true triaxial loading system, in which the transducer was tested under different stress states in a cement mortar body. The results indicate the transducer performs well and is applicable for soft rock stress measurement.