TRIFARIOUS FBG SENSOR STRAIN TRANSFER CHARACTERISTICS AND ITS APPLICATION TO TUNNEL EXCAVATION MODEL TEST

Based on the similarity model material, the trifarious FBG strain sensor which is suitable for model test is developed. It overcomes the shortages of traditional fiber strain sensors. It simplifies the mechanics transferring process. The finite element method is adopted to emphatically analyze the effect of colloid elastic modulus to strain transfer characteristics of the FBG strain sensor. Then the colloid with elastic modulus 300MPa is selected in the experiment. The strain transferring coefficient of the sensor is 0.662, and the sensitivity is 0.794pm -1.The FBG strain sensors are used in tunnel excavation model test to explore the strain distributing situation in surrounding rock by supporting-step-excavation method, supporting-whole-section-excavation method and non-support and whole-section excavation method. The monitoring results of the FBG strain sensors show that surrounding rock is more stable when the supporting-step-excavation method is adopted. The experiment provides reliable data support for research different excavation method and supporting method of the tunnel.