Research on the penetration performance of rotary ground-penetrating radar in detecting coal-rock interfaces of roofs based on numerical simulation and actual exploration

Abstract

Determining the precise boundary of coal seams is a significant challenge in the field of intelligent coal mining. Traditional drilling methods have proven inefficient in detecting the coal-rock interface of the roof, failing to meet the standards required for smart mining operations. To overcome this limitation, this paper proposes a novel rotating ground-penetrating radar (GPR) observation method for detecting the coal-rock interface,the GPR will be installed within 2 m of the air layer thickness beneath the coal roof in the coal working face, enabling omnidirectional 3D rotational detection. To study the penetration characteristics of the rotating GPR in the coal-rock interface of the roof, a refined numerical model was established. The model incorporates four different gangue content levels: 0 %, 0.1 %, 0.5 %, and 5 %, and includes four detection targets: “Coal-Immediate Roof”,“Immediate Roof-Main Roof”,cavity, and “Air-Coal”. The numerical simulation orthogonal experiment investigated the waveform characteristics, energy spectrum variations, and imaging features of GPR antennae at three different central frequencies: 50 MHz, 100 MHz, and 200 MHz. This analysis aids in selecting the appropriate detection frequency based on observed patterns in energy spectrum changes and imaging characteristics. Additionally, the paper analyzes the influence of the coal wall, floor, and random surfaces (“Immediate Roof-Main Roof”) on target recognition, comparing the identification effects of different acquisition methods and modeling approaches. This study provides new insights into non-destructive detection of coal-rock interfaces in mine roofs by validating the advantages of the proposed detection method and the feasibility of frequency selection with measured examples.