Longwall Floor Horizon Sensing

Effective control of the longwall mining horizon is critical to maintaining productivity, safety, and coal quality. While longwall automation technologies such as LASC have improved face alignment, the absence of real-time sensing of subsurface geology remains a key limitation to automated horizon control. This project investigated the feasibility of deploying ground penetrating radar (GPR) technology in an underground coal mining environment to support longwall floor horizon control under production conditions.

Rather than developing a new GPR sensor, the project focused on enabling the deployment of commercially available GPR equipment underground by addressing the practical barriers that have historically prevented its use. A key outcome was the design, development, and certification of a novel non-metallic statically pressurised enclosure suitable for housing unprotected electronic equipment in underground coal mines. The enclosure demonstrated effective pressure retention and mechanical integrity during operation and was designed to support a range of custom sizes. While developed specifically to enable GPR deployment in this project, the certified enclosure platform has broader applicability to other underground sensing and monitoring technologies requiring non-metallic, explosion-protected housings.

The integrated GPR system was installed on a production longwall and operated during normal mining activities. During operation, the system remained stationary for extended periods and moved forward only in short, discrete steps as the longwall retreated, rather than travelling continuously. A pseudo-odometry signal derived from instrumented roof support DA ram data was successfully used to convert time-based GPR measurements into distance-referenced datasets suitable for interpretation.

Results from the production trial demonstrated that the GPR system could successfully detect the key geological interface within the longwall floor, namely the coal-claystone boundary. Validation drilling confirmed strong agreement between interpreted GPR responses and measured layer thickness. Additional comparison with independently collected marker band data showed consistency between the GPR-derived seam floor position and established horizon control references used at the host site.

The trial also provided important insight into practical deployment considerations. While the explosion-protected enclosure maintained integrity and pressurisation throughout operation, mechanical damage to the enclosure hood highlighted the need for future system designs to explicitly account for physical interaction with other equipment.

Overall, the project demonstrated that commercially available GPR technology can be deployed and operated in a production longwall environment when supported by appropriate enclosure design, certification, and system integration. In addition to validating sensing performance, the project delivered a certified non-metallic enclosure platform with broader applicability to future underground sensing systems. These outcomes provide a clear and defensible pathway for further development of GPR-based horizon control sensing to support improved longwall mining operations.