The vast majority of minerals, by tonnage and type, are recovered from surface mining activities. As you know, surface mining is used to recover near-surface mineral deposits, where it is economically feasible to remove the overburden to gain access to the minerals of interest. Surface mining is typically a large scale and bulk operation. In general, the surface mining methods are the lowest cost of any mining methods. Of course, some minerals of economic interest lie too deep to be economically recovered by a surface method, whereas others cannot be mined by a surface method because of environmental or social constraints, which necessitate using an underground mining method to recover those deposits.
Let’s take a look at the number of surface vs underground mining operations for each mining sector in the US.
Figure 9.1.1: Number of surface vs. underground mining operations for US mining sectors
| Sector | Underground | Surface |
|---|---|---|
| Coal | 233 | 758 |
| Metal | 89 | 191 |
| Nonmetal | 39 | 820 |
| Stone | 111 | 4,160 |
| Sand and Gravel | 0 | 6,162 |
Not only are there more surface than underground mines, but also the average productivity is higher for surface operations. The average productivity (average tons per miner per hour) for surface mining is around three times the value for underground mining. Here is a summary of coal mine productivity for different years (the values are tons per miner per hour) to illustrate the difference in productivity, as well as changes that have occurred over the years.
| Year | Underground | Surface | All Mines |
|---|---|---|---|
| 1980 | 1.21 | 3.27 | 1.93 |
| 1990 | 2.54 | 5.94 | 3.83 |
| 2000 | 4.15 | 11.01 | 6.99 |
| 2010 | 2.89 | 9.47 | 5.55 |
| 2015 | 3.45 | 10.95 | 6.28 |
The depth and breadth of engineering required for surface as compared to underground mining is arguably significantly less. Nonetheless, good engineering is the key to sustainable operations; and it all begins with mine planning.
Surface Mining (7:19)
Transcript: Surface Mining (7:19)
Hello and welcome to this module of Introduction to Mining Engineering. I'm your instructor, Dr. Shekhar Bhattacharyya.
In this session, we will explore surface mining in more detail, a critical method in the mining industry that is responsible for the majority of mineral production in the United States and globally. We will examine key mining methods, planning and design, operational cycles, equipment, environmental and safety aspects, and conclude with sustainability considerations and a case study.
Let's begin with a brief recap: What is surface mining?
Surface mining involves removing the overburden—the soil and rock layers covering valuable mineral deposits—to access the ore beneath. It is most cost-effective for shallow and extensive ore bodies such as coal, copper, iron, bauxite, and aggregates. Its advantages include high production rates, lower cost per ton, and easier access to deposits.
Now, let's look at the main surface mining methods.
The first is open-pit mining, which is used for hard rock minerals such as copper, iron, and gold. It features stepped benches that improve both safety and efficiency.
Next is strip mining, which is common for horizontal layered deposits such as coal. In this method, overburden is removed in long strips.
Another method is quarrying, which targets construction materials such as limestone, marble, and granite.
There is also mountaintop removal, practiced primarily in Appalachian coalfields, where entire summit layers are removed to access coal seams.
Bucket-wheel excavator operations are used for continuous mining in large, uniform deposits, particularly lignite deposits such as those found in Germany.
Highwall mining combines surface and underground mining approaches to recover residual ore from highwalls.
We also have specialized methods that include hydraulic mining, placer mining, and in-situ leaching for soluble or unconsolidated deposits.
Now, let's discuss mine planning and design.
Effective mine planning begins with comprehensive geological and geotechnical investigations. These include slope stability analysis, hydrology studies, and rock mechanics testing. Pit optimization tools, such as the Lerchs-Grossmann algorithm, help balance economic returns with safety considerations.
Key design elements include:
Pit and waste dump design with optimal slope angles
Bench geometry, including bench height, width, and face angle
Haul road layouts designed for large mining trucks
Phased mining, or pushbacks, to improve cash flow
Progressive reclamation throughout the life of the mine
Turning to unit operations in surface mining, the typical mining cycle includes:
Drilling and blasting, when necessary
Excavation using shovels, loaders, or draglines
Hauling using trucks or conveyors
Crushing and stockpiling
Progressive reclamation whenever possible
Key equipment used in surface mining operations includes rotary and blast-hole drills, hydraulic shovels, electric rope shovels, draglines for large-scale overburden removal (especially in coal mining), haul trucks with capacities up to 400 tons, conveyor systems, and in-pit crushers.
Support equipment includes dozers, graders, and other auxiliary equipment necessary for efficient operations.
Let's now consider environmental and safety challenges in surface mining.
Environmental challenges include dust, noise, vibration, sedimentation, water pollution, and habitat destruction. Mitigation measures include dust suppression systems, controlled blasting practices, sediment control measures, and progressive reclamation.
Important safety measures include:
Monitoring highwall and slope stability
Maintaining clear traffic management systems
Providing operator training
Conducting regular inspections
Implementing fatigue management programs
There are also important regulatory frameworks governing surface mining, particularly in the United States. Coal surface mining is regulated under the Surface Mining Control and Reclamation Act (SMCRA), while other minerals are generally regulated through federal and state permitting processes.
Reclamation requirements typically include backfilling, grading, topsoil replacement, revegetation, and related restoration activities. Financial bonds help ensure that reclamation work is completed.
Regarding sustainability and community engagement, modern surface mining emphasizes water recycling systems, progressive reclamation, restoration using native vegetation, and active engagement with local communities and stakeholders to maintain a social license to operate.
There is a case study available in the Canvas module on phosphate surface mining in Florida. Phosphate mining in Florida uses strip mining and hydraulic dredging. Overburden is removed, and the phosphate-bearing matrix is pumped to beneficiation plants. Reclamation efforts include wetland restoration and the creation of pit lakes that may be used for aquaculture.
In conclusion, surface mining is vital for infrastructure, energy production, and manufacturing. While it offers significant economic advantages, it must be designed and managed with a careful balance of productivity, safety, environmental protection, and community trust.
As future mining engineers, your role will be to integrate technical expertise with responsible stewardship.
That's all for today. I'll see you soon in the next module. Until then, keep learning and stay safe.
Learning Outcomes
At the successful completion of this module, you should be able to:
- demonstrate knowledge of the goals of long-range, short-range, and production planning;
- demonstrate an understanding of the Mathieson list of objectives for the extraction planning process, and explain in specific terms how those objectives would affect planning and mining activities;
- lay out a bench for an open pit mine, labeling the toe, crest, the face angle, bench width and height, face angle, slope or pit angle, and the berm location and height. Describe the parameters and considerations that will affect the design of the bench;
- demonstrate knowledge of the mechanical and aqueous surface mining methods, and specifically for each method:
- describe the factors that favor the choice of the method over other methods,
- describe the life cycle and sequence of operation,
- sketch the method to illustrate its defining characteristics,
- list the type of equipment normally associated with the method, and
- name examples of commodities that are commonly mined using the method.
What is due for Module 9?
This module will take us two weeks to complete. Please refer to the Course Syllabus for specific time frames and due dates. Specific directions for the assignment below can be found within this lesson.
| Activity | Location | Submitting Your Work |
|---|---|---|
| Read |
| No Submission |
| Complete |
| Canvas |
Questions?
Each week an announcement is sent out in which you will have the opportunity to contribute questions about the topics you are learning about in this course. You are encouraged to engage in these discussions. The more we talk about these ideas and share our thoughts, the more we can learn from each other.