NIOSH ground control safety research program at Spokane, Washington, is exploring applications of photogrammetry to rock mass and support monitoring. This paper describes two ways photogrammetric techniques are being used. First, photogrammetric data of laboratory testing is being used to correlate energy input and support deformation. This information can be used to infer remaining support toughness after ground deformation events. This technique is also demonstrated in a field application. Second, field photogrammetric data is compared to crackmeter data from a deep underground mine. Accuracies were found to average 8 mm, but have produced results within 0.2 mm of true displacement, as measured by crackmeters. Application of these techniques consists of monitoring overall fault activity by monitoring multiple points around the crackmeter. A case study is provided in which a crackmeter is clearly shown to have provided insufficient information regarding overall fault ground deformation. Photogrammetry is proving to be a useful ground monitoring tool due to its unobtrusiveness and ease of use.

Deformation and support conditions in underground mines are typically monitored through visual inspection and geotechnical instrumentation. However, the subjectivity of visual observation techniques can result in ambiguous or incomplete analyses with little quantifiable data. Monitoring displacements with conventional instrumentation can be expensive and time-consuming, and the information collected is typically limited to just a few locations. Moreover, conventional methods usually provide vector rather than tensor descriptions of geometry changes, the latter of which offer greater insight into rock movements and potential ground fall hazards. To address these issues, researchers from the National Institute for Occupational Safety and Health's Spokane Mining Research Division have developed and evaluated photogrammetric systems for ground control monitoring applications in underground mines. In cooperation with the Hecla Mining Company, photogrammetric surveys were conducted over a three-year period at the Lucky Friday mine in northern Idaho, United States of America, as underhand cut-and-fill mining methods were used to mine Ag-Pb-Zn ore in rockburst-prone ground conditions at depths approaching 2,100 metres. A photogrammetric system was developed for underground use at the mine that is not only mobile, rugged, and relatively inexpensive, but also capable of producing measurements comparable to conventional displacement-measuring instrumentation. This paper describes the components of the photogrammetric system, discusses the use of point cloud analyses from photogrammetric surveys to monitor bulk deformation in underground entries, and explains the advantages of full tensor descriptions of three-dimensional (3D) ground movement, particularly in regard to the interpretation of potential movement along fault intercepts. The practical use of photogrammetry to augment measurements from conventional instruments, such as crackmeters, is presented, as well as the use of photogrammetric data in conjunction with 3D visualisation software to synthesise and integrate complex information from diverse sources including geology, mining configuration, seismicity, and geotechnical instrumentation.

Corrosion of ground support can lead to falls of ground, posing a significant risk to miner safety. To address this problem, the Spokane Mining Research Division of the National Institute for Occupational Safety and Health is investigating ground support corrosion at the Greens Creek mine, located near Juneau, Alaska, United States of America. Field and laboratory studies include surveys of weld-wire mesh corrosion, rock mass conductivity measurements, and sample analyses using a scanning electron microscope, energy dispersive spectrometry, and Fourier transform infrared spectrometry. Current field studies demonstrate a correlation of rock mass conductivity to the degree of weld-wire mesh corrosion and the relationship of ground conductivity surveys to support corrosion potential. Laboratory analyses of mine samples identify the presence of sulphate, which is a determinant for sulphate reducing bacteria activity. Identification of sulphate reducing bacteria (SRB) would provide evidence for microbial influenced corrosion in this mine. Ongoing research is evaluating methods of SRB inhibition. These results provide engineers with a means to map corrosion potential of the rock mass, and identify a number of paths for design of focused mitigation efforts for problem areas.

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The Spokane Mining Research Division (SMRD), of the U.S. National Institute for Occupational Safety and Health (NIOSH) is continuing research on the mechanical behavior of primary surface support components in mining ground support systems. Mining ground control safety often depends on supporting, or at least containing, the ground between rockbolts using what is referred to as local, surface, or areal ground support. Steel mesh, in various combinations and with other components, is often used to accomplish this, as well as to retain loose rock. Local ground support is an integral part of maintaining a safe underground operation. However, as underground hard rock mining continues moving towards automation, increased challenges regarding support installation and maintenance will create a need for a new generation of mesh support systems. Advanced materials engineering has created various synthetic meshes to meet this need. This study begins a process of compiling technical information on multiple types of mesh performance, leading to an eventual comprehensive index for industry use. Using SMRD’s high-energy high-deformation (HEHD) testing machine, a program was developed to assess the behavior of a variety of steel and synthetic mesh products in quasi-static loading conditions. The data from these tests were used for comparative analyses of the force-displacement and energy-displacement characteristics of conventional steel meshes to synthetic meshes. Considerations were also given to several additional operational and performance factors, including corrosivity, flammability, durability, and handling. This work was completed as part of the SMRD mission of improving the health and safety of underground metal mine workers, and this paper presents the findings of these tests.