Theoretical Study of Coupling Mechanism between FBG and Shock Waves of Rock Burst

Shiming Wei,Zesheng Zhang,Yao Wang

doi:10.4236/wjet.2020.84057

Shiming Wei, Zesheng Zhang + Show 1 more

Open Access

https://doi.org/10.4236/wjet.2020.84057

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Abstract

To achieve the monitor of rock burst in coal mine with fiber Bragg grating (FBG) sensing, the coupling mechanism between FBG and shock waves was theoretically analyzed. Based on Housner’s random shock model, the coupling mechanism between shock waves and FBG was theoretically analyzed. The result shows that the wave will change the period &#581 and effective refractive index n of FBG, and further affect the initial wavelength value. The amplitude, phase and frequency of shock wave are directly related to the wavelength drifts of FBG. The transmitting velocity of shock wave in rock is affected by lithologic characteristics. The Elastic modulus, density and Poisson’s ratio of rock influence the initial wavelength value of FBG. This study provided a theoretical basis and practical application guidance for coal or rock burst monitoring with FBG sensing.

Highlights

With mining depth of China increasing gradually, the occurrence rate of rock burst increases [1] [2]
This study provided a theoretical basis and practical application guidance for coal or rock burst monitoring with fiber Bragg grating (FBG) sensing
According to Equation (5), when shock waves of rock burst are monitored by the FBG sensor, the waves will be coupled with the FBG, and the initial wavelength of the FBG will be changed

Summary

Introduction

With mining depth of China increasing gradually, the occurrence rate of rock burst increases [1] [2]. Wu Jianhui et al [20], based on FBG sensing, set up a monitoring system of seismic wave with sensitivity of 0.54 pm/ms2 Because both earthquake and rock burst origin from sudden release of energy under high compressive stress concentration in rock, the shock waves generated are similar. Wang Jianda et al [21] applied FBG sensing to underground coal mines, and developed early dynamic warning technology of rock burst as the early warning indexes of monitoring system of mining stress and stress gradient. The research on mechanism of FBG sensing for rock burst, especially the transmission characteristics and influencing factors of shock waves in different rock are not involved. 2. Mechanism of Lithologic Characteristics for Shock Wave Monitoring of Rock Burst with FBG Sensing

Coupling Mechanism between Shock Waves and FBG

Analysis of Influence Mechanism of Lithologic Characteristics

Conclusions