Risks & Dangers Faults Cause in Open Pits & Surface Piles
Faults in open pits cause problems, as block movements in terms of geology and production, and cause problems as mass slides, landslides, water outflows on slopes in terms of geotechnical issues. As the open cut expands and deepens during the operation, faults are revealed, and in the ongoing process, you witness the ground tending to move along these faults, which were detected in the upper levels perhaps years ago. In addition to the geotechnical problems with the groundwater reaches saturation as a result of long-term heavy rain or snowmelt, you will experience problems reasoned by sliced & slipped orebody while you need a clean extraction of ore body. If we have collected sufficient data at the planning stage to understand the underground and identified the dangers that we need to foresee with knowledge and experience, we can quickly get what we need and complete the operation without any problems. Nature will increase the price to be paid for every minute we hesitate, and will issue the bill when the time comes.
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Procedures take the burden off employees to take initiative. In open pit operations, where downtimes are of utmost importance, it is naturally quite difficult to decide that there is a danger and to stop work. It is important to foresee where the danger may come from and to keep the development of the danger under control step by step. If there is no design above the critical slope angle in open pit mines, the source of all the problems you will experience will be faulting and the resulting crack systems, even if your problem is in extremely weathered ground. In the steps and video file below, the problems that faults will cause in open pit mines and the practices that can be done to predict them are discussed. You can follow the details of the items in the video from our article below.
Since determining the definition or degree of danger is a subjective phenomenon and initiative, providing instructions with detailed preliminary definitions will help business managers to make the right decision at the right time.
Cutaway Topics
You can also follow the topics in the video with the item number. It will be useful to stop the video at the point where the relevant topic title is found, watch the episode again, and re-evaluate it in detail.
Additionally, you can explore the related articles listed below.
1. Let's state from the beginning: You must examine all the data you will obtain in a 3D digital environment.
This process requires meticulous follow-up, assign your personnel with sufficient equipment (Geotechnical engineers, geology, mining team), as well as train your personnel working in the mine at a basic level to provide information in important situations. Make slope and level maps regularly and on time. Calibrate your structural criteria and compass measurements as a team, and get constant help from the survey department if possible. Obtain topography data periodically by drone / aerial measurement and photography, and compare it repeatedly with previous data. Determine criterias by which you will log your drillholes, and follow the appropriate procedure to obtain photographs of the drilling cores in the most meticulous way. You will use all of this data for frequent retrospective confirmation purposes on new levels / floors or in anticipated danger situations. Rather than evaluating it in parts, the only place where you can see all the data together by cross-checking and confirming it with each other, is the computer screen. Before the project begins, obtain a 3D design program suitable for your work. By including data from your in-pit seismic or video monitoring tools, you can examine all the structural elements you have created one after the other and foresee possible dangers well in advance.
2. Understand your mineralization: The "issue" that forms the ore may have weakened the surrounding rock
While mineralisation precipitated millions of years ago, it may naturally cause some changes in the rock in which it is located. Although these changes, which constitute negative conditions for the operation, will harden over time and become somewhat stable, they will bring about some risks in the production pits that will be excavated. You can foresee these risks, such as alteration clays and weathering in rock, with the concept which you have developed through your work from the exploration process to the beginning of the mining project. You can obtain positive results by supporting geochemistry and hydrogeology laboratory studies.
3. Fault slip on ore body: What does this to ore body, imagine what it could do to slopes...
When the fault slip on ore body is concerned, there will be many difficulties in terms of both modeling and production. Separating and spotting the ore zones requires serious experience, especially in production, grade control work and when updating the grade control model. It would be beneficial to use all your means to see the big picture by observing the pit level floor from the upper elevations or photographing it from the air (with a drone), if possible, during grade control work or at convenient times. It will be very useful to show the results you have obtained, especially the locations of large faults, in 3D on the computer screen to samplers / spotters in order to turn them into an advantage in production. We can say that ore contamination in production occurs most in such regions where faults have vertical and horizontal slips that are difficult to understand in which direction. Considering this situation, whenever possible, equip the relevant staff with the most up-to-date information you have obtained and ensure that they pass on to each other during shifts.
Do not forget that you will also see the faults that you detect on the ground (Before project) by observing the slips on the slopes, or conversely, do not forget that the fault you detect on the slope will have a continuation on the ground. Under all circumstances, follow the fault you observe in the ground, if possible, by scraping the ground in a particular width with bulldozer or grader. When you fully examine the fault behavior you will observe in your pit, you will see that it is in harmony. When you detect faults that are sometimes opposite each other, sometimes parallel to each other and arranged periodically, you will maximize your modeling and therefore your command of the structural elements in the open cut.
Before going out to the field for grade control studies, it will make your job much easier if you examine the upper level maps and note the lines / slices where you expect to encounter important faults and the locations on them on your map form.
4. Faults are best observed in the “open pit”, work your fingers to the bone: Mapping
You can see the best geological outcrops on earth in the slopes, level floor and production faces within the open pit mine. The main reason for this is that you can find the widest and clearest sections and the opportunity to observe the big picture in these environments so that you can distinguish structural and lithological units. Open pit mining, which reveals the freshest undecomposed rock protected from surface conditions, provides unique opportunities for us to examine what nature can do, especially after a long rainstorm, when the dust on the pit surfaces is washed away and the rock gains a bright appearance with this moisture. When it comes to such an environment, do a job safety analysis (JSA) without wasting time and go down to the pit with your map form and camera. You will be quite satisfied when you examine the images and data you obtained before the slopes dried. If you are in a region or season with low rainfall, it is very important to do your mapping immediately after the excavator’s slope scraping. Mapping and photography will provide you with data not only for production but also to foresee all possible hazards.
5. Drillholes: We spent so much money, those “cylindrical stone pipes” must be useful
Drillholes are your most important and reliable pre-operation data not only for your resource modeling and estimation but also for your geotechnical evaluations. You can make the most reliable comments about the underground by extending the fault directions and dips you have obtained with your mapping on the surface and within the operation, and combining them with the faults you have detected in the drillholes. Naturally, you will need to do this through 3D design programs. In this case, the importance of drilling plans and execution, therefore the drilling log and photographs, and therefore your coreyard / core shack, reveals itself here.
6. Introduce faults and ore body to your colleagues: A geologist wasn't the first to see these in the world
Or maybe a geologist, or may have become one later. Anyway…
Operation activities are very fast-paced processes, and the resulting outcrop can be produced within a few hours and sent to the stockpile or covered with dust in the ongoing excavation environment. As a geologist and mining engineer, you may need to see all kinds of structural elements when the outcrop first forms. Even if you are not there at the time, the operators doing the excavation should notify you when they see this structural difference. Train all your staff, if possible, stop production and demonstrate on-site when you detect faults or special situations in the ore body. You will gain more than this downtime that you will lose for one or a few times.
To all your colleagues; tell them to immediately mark the faults, fault-related fractures or gaps they detect with spray paint or stakes, and if possible, completely barricade the area where the cracks extend and inform the relevant geotechnical units / department immediately. The smallest detection can prevent huge dangers.
7. As the operation progresses, faults will become more difficult to detect: Catch and take them out from where they are hidden
During the excavation, the dust and particles in the environment will soon cover the details on the slopes, and in addition, as the fresh rock surface gets rid of moisture, the surfaces will turn into dry and light tones. Or, on the contrary, the mud flowing with the rain will plaster the slopes, or even more, the faults will become visually unrecognizable as the argillized, weathered rock swells. These situations will generally be the biggest problems encountered in making the distinction under all circumstances.
Groundwater rising or mobilizing with rainfall will not fail to reveal itself along the faults extending into the pit. Of course, we should not forget that every natural phenomenon that benefits us has a price, because the fractured and clayey zone of variable thickness that forms along the fault surfaces will use this water against us. Clay and clay-containing weathered lithology, which absorbs water and swells, will push the blocks towards the pit space opened in the direction of the fault surfaces. It should not be forgotten that the hourglass turns upside down as soon as you start applying this force, you should know that you do not have much time. Tens of thousands of cubic meters of swollen material released from the fault surfaces will attack the open cut in block form. This situation will usually manifest itself when the rock becomes saturated with water as a result of several days of continuous heavy rain activity.
8. Follow the geomorphology, starting with the pit excavation: Continue tracing by smell
You must have certain acceptances in the exploration process regarding the main geological elements prevailing in the region, the late-stage structural movements and their directions. When you examine the latest geomorphological structures, your ideas about what will sit underground and in what position will develop with these assumptions. Simply put, it will be very useful to examine the faults you have drawn in 3 dimensions due to sudden elevation changes in streams or hills and discuss them before or during the design of pit plan.
9. Landslides occur on earth: Or the block under the ground is sliding, do we only see the top?
Although what we define as a landslide is generally a vertical sliding movement in the soil, it should not be forgotten that the rock under the soil is also included in this movement. Soil, which we define as a partially free material consisting of organic content such as fine rock crumbs of sand and clay, plants and residues, which is generally represented on the earth with a thickness of a few meters, loses its intergranular adhesion as it becomes saturated with water and is destroyed by gravity as a result of the sudden change in the angle of internal friction. takes action. What we often see on slopes is a simple landslide consisting of soil or fine material flowing.
Open pit or surface landslides, unlike soil or fine material flow, can also develop with the sliding of blocks that lose their adhesion along deeper fault surfaces. Open pits are normally areas of instability open to mass movement in the existing equilibrium topography. The force that activates the blocks here may be the sudden triggering of liquefaction activity due to water-saturated swelling clays and groundwater on the discontinuity surfaces.
10. Pay attention to the pile you place on the fault: There may be a loose mass under the ground
When waste, ore and heap leach stocks are placed on fault surfaces extending into pits, slopes and slopes, the stability of the ground on which these masses rest may change suddenly with seasonal conditions. Water activated by precipitation or melting snow can penetrate into the structure of low-hardness clastic piles and increase the bulk density values by more than 1.5 times, which will cause a serious increase in mass. This sudden load increase may cause the ground along the fault surfaces to begin to migrate towards open mining or the slope where it can be released. As a result, it should not be forgotten that large blocks may slide under the thin or thick rock mass that may flow into the pit or on the slope, and that the starting point of this movement may be fault surfaces.
Remember that the stack you make will have its own internal friction angle, but this should not be relied on due to precipitation and changing humidity. Note that the intergranular adhesion of the stack is created solely by gravity rather than rock hardening, and that with water saturation this adhesion disappears and the grains become mobile. The filling you place on the faults can be deeply activated by water percolating along the fault surface due to groundwater saturation, fundamentally disrupting the stability of the sequence.
11. Ground survey: Should be examined in 3D digital environment
Large-scale ground investigation should be carried out not with traditional vertical drillings, but with expertly planned directional and inclined drilling programs that will scan all underground structures based on data obtained from geological mapping and geomorphology. Otherwise, there is a high probability of missing many structural elements.
In the ground survey conducted for the legal procedure related to mining operations, faults should be modeled by creating 3D projects, and geophysical studies should be used if necessary. Although it is not possible to detect faults in IP and resistivity studies, which are frequently used in mining studies, seismic sections provide the opportunity to obtain extremely useful results, especially in projects that include different lithologies and faults cutting them. Legally making such geophysical applications mandatory for suitable projects will be beneficial to gain comparative structural confirmation.
12. Do not insist on whether there is an example somewhere: If the subject is "danger", you may be the one experiencing the firsts.
Unless major accidents occur, mining has a very secretive literature. Sometimes near misses, sometimes cheap misses or small-scale mass movements on the rock can be neglected, rightfully or unjustly, by taking into account the planning and execution process during operation. Just as the relationship of occupational safety with statistics rather than feelings is consistent, the problems experienced with faults in open pits and underground mines, if any, will be compatible with the data kept. While making your pit plans, it is very important to cross-check your designs and get the opinion of different sciences. You can only foresee risks and opportunities in applications such as sustainability and future plans, mine expansion and capacity increase through meetings and evaluations with all relevant units/departments. It is very important that the units that will deal with this issue prefer “standard and clear” sentences that are understood by all concerned in the meeting and are scaled according to certain criteria, rather than avoiding responsibility and making round and vague sentences. Jargon in meetings and communication should not bore people, should not cause anxiety, and should not allow the other person’s ego to come into play.
In summary, obtaining clean and clear data with the criteria you will determine from the beginning, making decisions together with all units, and supporting these decisions by consulting experienced experts on the subject, if possible, will prevent all possible bad experiences.
Subjects discussed in this article may overlap with your mineral exploration, modeling, mining operation and business development issues and may provide solutions for those. However, remember that various factors specific to your business may bring about different challenges. Therefore, seek support from expert consultants to evaluate all data together in order to convert potential into profit most efficiently.
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