Optical Fiber Frequency Shift Characterization of Overburden Deformation in Short-Distance Coal Seam Mining

Dingding Zhang,Jing Chai,Jianfeng Yang,Zhengshuai Wang,Qiang Chen

doi:10.1155/2021/1751256

Abstract

Overburden deformation is an important concern for the safe and green mining of coal resources. Similarity simulation testing is the main approach used to study the deformation characteristics of the overburden in coal mining. In the application of Brillouin optical time-domain analysis (BOTDA) in similarity simulation tests, the capability of distributed optical fiber sensing (DOFS) to detect the characteristics of the overburden deformation and the evolution is a key factor affecting the testing accuracy. In this study, the relationships between DOFS and overburden deformation and the face impact pressure under geological conditions in short-distance coal seam mining were explored. The results show that DOFS can be used to monitor the strain conditions of the overburden during the entire mining process and can provide the peak positions of the advance support pressure on the face. A DOFS characterization model for investigating the spatial and temporal evolutions of overburden deformation was established. A new method of characterizing the face impact pressure based on the fiber frequency shift variation was developed. The method was demonstrated to be effective through comparison of monitored results of impact pressure counts detected using pressure sensors. The characteristics of the face impact pressure in short-distance coal seam mining were obtained. The results of this study provide valuable guidance for the development of similarity simulation testing and intelligent mining engineering techniques.

Highlights

The mining of coal resources can destroy the overburden rock layers, resulting in soil and water losses at the ground surface, damage to the regional ecological balance, and many other serious environmental problems [1,2,3]
Critical issues in applying distributed optical fiber sensing to monitoring overburden deformation using similarity simulation tests were investigated
(1) Overburden strain monitoring during the entire mining process was achieved at different relative positions between the distributed optical fiber sensors and the face

Summary

Introduction

The mining of coal resources can destroy the overburden rock layers, resulting in soil and water losses at the ground surface, damage to the regional ecological balance, and many other serious environmental problems [1,2,3]. Zhang et al [27] used inclined drilling to implant distributed sensing optical cables in the sampling field of their similarity simulation test in order to accomplish strain field monitoring of overburden deformation during mining. Chai et al [28] applied the distributed strain fiber technique to a three-dimensional physical similarity simulation test to conduct quantitative characterization of the internal deformation and failure of mining-induced overburden. The similarity simulation test monitoring system included a NX-6055 Brillouin scattering optical time-domain analyzer, distributed optical fiber sensors, CL-YB-114 pressure sensors, and a micrometer. Four vertically distributed optical fiber sensors (V1, V2, V3, and V4) were embedded in the similarity model to monitor the deformation characteristics of the overlying rocks. Each fiber sensor was connected in series with another fiber sensor and connected with an NBX6055 optical stress analyzer

Analysis of Monitoring Results

Optical Fiber Monitoring Analysis of the Face Impact Pressure

Conclusions