August 2012

Preview: The Slope Rehabilitation tool

Reconditioning of slopes into lasting, permanent rehabilitated slopes can be a time-intensive process. The new MineSight Slope Rehabilitation tool will revolutionize the way in which slopes are manipulated and processed. An easy to install plugin for MS3D, it allows you to quickly adjust the slope angles of surfaces.

Not only can the tool handle the conversion of complex existing surfaces, converting from benches and road cuts into smoothed, more natural slopes, but it also accounts for the volumetrics of the adjusted slopes. Any material that is removed (cut) as a result of the slope adjustment will be accounted for elsewhere (filled).

Image 1. The Slope Rehabilitation tool as accessed from OP Eng tools.

The process starts by selecting the rehabilitation surface. Slope angle parameters and any restrictions to the area affected are required before the rehabilitation of the slope can begin. The panel interface used to select surfaces, angles and polygons is seen in image 1.

The tool works by converting the rehabilitated surface into a virtual gridded surface based on the engine parameters. This surface is then manipulated according to the entered slope angles. To adjust a slope, the surface is firstly selected in the rehabilitated surface option. Two options allow the surface to be selected either through the object contents browser or by selecting the open object in the viewer.

Image 2. Target dump with boundary polygon (red).

Once the appropriate surface is selected, a maximum slope angle can be entered in the default option. This option will apply the specified angle to the whole surface. Sometimes, you need to apply a resloping angle only to a certain area and not to the whole surface, like in image 2. In the case above, only the dump is being resloped and not the surrounding topography. To restrict the influence of the Slope Rehabilitation tool, a polygon is used to constrain the target area. The maximum slope angle entered for the polygon affects everything within the polygon, and the default angle now affects everything outside of the polygon. Multiple polygons can be used with varying angles. Where polygons overlap, the lower angle will be chosen.

The engine parameters dx and dy control the size of the gridded surface. These are automatically populated with the default cell sizes provided in the project settings. Changing these parameters will affect the resolution of the produced surface and consequently how material is moved around when resloping. The decrement represents the axis of elevation, but is used as an adjustable factor to control the amount of material that is removed in a single iteration. So, when using a dz value of 0.1, this defines a volume of dx*dy*0.1 that can be moved. This volume represents the capacity of your equipment. Accurately considering equipment capacity in this way will give a realistic operational design.

Surfaces selected with the Slope Rehabilitation tool are required to have sufficient area for material to be moved and reallocated. Surfaces that do not have sufficient surface area for a slope to be reordered will still be adjusted. But the surface perimeter will become detached from the original elevation and not stretched. It is instantly apparent in such cases that the output is unsuited and can be corrected by adding the surrounding topography to allow material to be successfully moved and reordered.

Image 3. Cross-sectional view of the original dump surface (blue) and modified surface (red).

In the example seen in Images 3 and 4, a dump surface is rehabilitated from an initial operating angle of 37° to a permanent rehabilitated slope angle of 30°. In order to specify only the resloping of the dump, a polygon was picked to target only the dump area, as seen in Image 2. The maximum slope of the polygon entered was given as 30° and the default angle was changed to 89° so no other slope outside the polygon would be affected. Image 3 clearly shows the rehabilitated surface (in red) being significantly different to the original surface (blue). Roads and benches have been removed and the overall slope angle reduced.

In order to meet the needs of reducing the slope angle, material was displaced outwards from the original footprint of the dump. The initial volume of the dump was 59,414,099 cubic meters and after rehabilitation the volume remained the same, but the surface area changed from 934,000 square meters to 112,000 square meters.

Image 4. A 3D view of how the slope has been rehabilitated (rehabilitated surface is in red with the original dump surface in yellow/purple and displayed for reference).

After a successful run of the Slope Rehabilitation tool, important information relating to the run appears in the message window. This includes the amount of cells used, the amount of cells left unresolved, the amount of passes made, the cut volume encountered and the push distance. The push distance is the cumulative distance that the displaced material from resloping requires moving. Such information is critical for calculating the time it will take to rehabilitate a slope. Prior to completion, a virtual preview of the modified surface will appear in the viewer. If unsatisfactory, this can be cleared by hitting ‘cancel’ or it can be committed to a selected geometry object by clicking ‘apply’.

While immediately applicable to the rehabilitation and mitigation of long-term dump surfaces, the tool has many other practical mining applications. For example, the Slope Rehabilitation tool can be used in a much larger context of resloping and smoothing any surface, whether a dump, pit wall or other type of surface. Ensuring slope stability based of geotechnical failure analysis is a critical part of safety on all mine sites. The Slope Rehabilitation tool is an additional function for engineers to quickly adjust and manipulate slopes without the need to remove material.

The cut and fill logic behind the tool enables advanced functionality much beyond CAD smoothing functions. The Slope Rehabilitation tool is another example of how MineSight is consistently responding to clients’ needs by developing new tools to quickly accomplish common workflows. Expect its release later this summer.