Mining
Slope Stability Movement and Monitoring in open pit mines
October 28, 2024 / Ignatius Kamwanje
Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement, Slope stability Analyses are generally aimed at understanding the causes of occurrence of slope failures, or other factors that can potentially trigger slope movements, resulting in a landslide, as well as at preventing the initiation of such movement, slowing it down or arresting it through mitigation measures.
The stability of a slope is essentially controlled by the ratio between the available shear strength and the acting shear stress which can be expressed in terms of a factor of safety.
Slope Monitoring techniques
There are various slope monitoring techniques ranging from simple visual inspection to complex GPS and radar scanning. All these techniques can be classified into conventional and modern-day techniques.
Conventional Techniques
Conventional or traditional monitoring techniques
These involve physical examination and mapping of tension cracks along the slope face. All mine personnel are involved in slope monitoring directly or indirectly. The initial stage in slope monitoring is a visual inspection, which is the foundation of any monitoring program. Mine workers search for any evident signs of deformation and then report them to management for a more thorough examination and monitoring. Routine inspections of active mine slope and dumps slopes is done by mine management.
Modern-Day Techniques
Ground-based radar devices and Global Positioning Systems
These are increasingly integrated into most large open-pit mines’ slope monitoring and management programs. Global Positioning System (GPS) is a navigation and positioning system that follows GPS satellites’ electro-magnetic signals. It measures the movements of slopes, landslides, and subsidence on a continuous-periodical basis. The amount of deformation and slope movements are calculated by comparing the starting and ending positions of the GPS stations. An an improvement to GPS, Differential GPS (DGPS) improves location precision in the range of operations of each system real-time information on slope stability and deformation rates. GPS is also being used as a control point for monitoring mine slope stability in conjunction with photogrammetry, total station networks, and remote sensing pictures. LiDAR (Light Detection and Ranging) directs a laser beam at the area of monitoring, which provides a graphical/digital depiction of slope and their relative motions based on the journey time of the radiation. They produce virtual replicas of the slope in minutes, similar to photographic images emphasizing crucial regions. Modern LiDAR scanners can be placed on static and mobile surveying platforms and instantly give Digital Elevation Models (DEM) that can precisely identify the deformation zone’s relative magnitude, displacement rate, and position.
Seismic Technique
Seismic technique has been used in open-cast mining to anticipate slope movements and failures. Micro-seismic events caused by tiny rock movements are collected by data recorders and relayed to the processing system. The events are then analysed to identify the zone of weakness, stress conditions, deformation mechanics, and deformation rate within the rock mass. Significant advancements in mine seismology information effectively reduce risks far before they occur.
Limitations of the Techniques
Selecting a proper monitoring system depends on several parameters, such as area coverage, mode of operation, cost, installation and maintenance concerns. Conventional methods are time-consuming and of low accuracy, and inclinometers, TDRs, extensometers, and LIDAR’s are not appropriate for real-time information and early failure prediction. slope monitoring radar has radically revolutionized the evaluation of geotechnical risk in surface mines.
Advancements
In the past years or so, radar has developed into a cutting-edge technology for monitoring pit wall movements in surface mining with real-time slope monitoring. The radar beam emitted by the antenna scans the slope faces vertically and horizontally. Movements along the slope are tracked both quickly and constantly, in addition to broad area coverage in all-weather conditions. In recent years, 3D imaging of the damaged surface has also been made available by radar monitoring. Radar can be either space-borne or ground-based depending on the application. Recently, Slope Stability Radar (SSR) advances have included broad areal coverage, remote operation from greater distances, and better spatial resolution. Radar systems pro-vide long-range monitoring, broad aerial coverage, and customized aerial coverage with sub-millimeter precision and accuracy. Techniques and recommendations for predicting the moment of failure or outlining the conditions of a predicted slope collapse offer in scientific literature. Getting an overview of the benefits and limitations of these different methods has become complex To simplify things, available works are classified on slope monitoring techniques based on the based on input and output data.
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