Stability monitoring of surrounding rock mass on a forked tunnel using both strain gauges and FBG sensors

A geo-mechanical physical model test is conducted to study the structural stability of the surrounding rock mass of a forked tunnel during excavations in this paper. The excavations of the tunnel would result in the redistributions of the stress field and even have significant impacts on the structural stability. To measure the variations of the real-time stress state of surrounding rock mass during excavations, two strain measuring techniques have been utilized to the geo-mechanical physical model test. One is the conventional static resistive strain measuring technique, and the other is the advanced Fiber Bragg Grating (FBG) sensing technique. The methods and working principles how to apply the two techniques on the stress field monitoring in the geo-mechanical physical model test are also introduced. The whole variation process of the stress field during excavations has been collected and analyzed. Then, the testing measuring results are compared with those obtained by numerical simulations, which are found to be in a good agreement. It is finally concluded that better experimental results for the stress field during excavations could only be obtained by the combination of the static resistive stain measuring technique and the FBG sensing technique. (C) 2019 Elsevier Ltd. All rights reserved.