Development and Performance Test of FBG Six-direction Pressure Sensor for Deep Soft Rock Stress Measurement

Rheological stress recovery method is an innovative in-situ stress measuring method for deep soft rock mass. This method is able to monitor the original rock stress and long term disturbance stress by embedding pressure sensors. A new FBG six-direction pressure sensor is designed and manufactured. The exterior shape of the sensor is sphere. The sphere contains six independent pressure sensing elements. Each sensing element is arranged at a different angle. The sensing element consists of a ram, spiral buckle and an arch-beam fiber grating strain gauge. The performance of the sensing element is calibrated by the method of multi-stage loading. The results show that all error indexes meet the requirements of the sensor with the accuracy level within 2%. This indicates that the sensor meets the actual use requirements.