Wire mesh has been used as ground support in mining since the 1950’s to protect the mine and its workers. Steel meshes are often deployed in open cast mines to provide dynamic surface support and to act as an immediate preventative measure for rockfalls and small landslides. The mesh may consist of welded wire or expanded or woven (chain link) metal. The wire used in manufacturing the mesh may vary widely in its physical and mechanical properties.
Various geospatial safety systems are now deployed on mine sites as tools to help monitor slope stability, but many of these technologies are unable to distinguish the wire mesh from the rock face behind because it is anchored so closely to the slope face. One technology that can overcome this problem is a LiDAR sensor that can perform echo digitization analysis, such as those used in SITEMONITOR LIVE +SLOPES.
Data from a mine showing wire mesh in yellow and the rock face behind in blue
LiDAR sensors scan the rock face with a pulsing laser beam. Each time the laser beam intersects an object, a portion of the pulse is reflected back towards the LiDAR sensor. Smaller objects return a smaller pulse and allow the remainder of the beam to continue until reaching another object. With echo digitization, each return pulse is processed to provide a discrete measured distance. As a result, where wire mesh is present in front of a rock face, the LiDAR sensor will receive two return pulses, and the instrument will calculate a distance to mesh (the first target) and to the rock face behind it (the last target).
Data showing the last returns of the laser scanner which has scanned the slope and eliminated the wire mesh
In practice, there may also be intermediate target echoes caused by vegetation, etc. All of these measured distances are present in the raw scan data, but SITEMONITOR LIVE software is designed to filter out all of the targets except the last target (the object furthest from the LiDAR sensor) for slope monitoring. SITEMONTOR LIVE +SLOPES also has the ability to automatically filter out other obstructions such as mining machinery that may move in front of the rock face, which would otherwise cause false alarms.
Wire mesh highlighted in yellow, with a cross-sectional view of the mesh provided on SITEMONITOR LIVE software.
GeoSLAM has developed SITEMONITOR LIVE to work in harmony with the surrounding safety measures and regulations installed by mine planners in their ever-changing environment. Not only can SITEMONITOR LIVE help analyse deformation and falling debris, but it can also monitor the accumulation of rock and ice behind the wire mesh which can compromise the mesh’s effectiveness.
Without echo digitization analysis filtering out the wire mesh and vegetation, crucial information from the monitoring area would be lost.