GEOG 000

Lesson 5.1: Introduction to the Cycle of Operations


Lesson 5.1: Introduction to the Cycle of Operations

The process of exploitation reduces to two fundamental operations: winning, i.e., freeing the ore from the orebody, although that term is rarely used in ordinary conversation; and materials handling, i.e., transporting the ore to the mineral processing plant. Winning and handling are repeated over and over again, i.e., they are cyclic.

The fundamental processes of freeing the ore fall into two categories. In softer deposits, we can use equipment to excavate or essentially “dig” the ore. In harder material, we will have to use explosives to blast the ore free from the orebody, and to blast the ore, we must first drill holes to place the explosive that will be used. Once the ore has been freed, it must be loaded so that it can be hauled.

Thus, the two fundamental operations defining the exploitation of ore, winning and materials handling, consist of the following unit operations:

Harder Materials: drill, blast, load, and haul

Softer Materials: excavate, load, and haul

These unit operations also define what is known as the basic production cycle.

Obviously softer and harder are relative terms and are deliberately vague. The compressive strength is an important parameter to separate ores into the “softer-harder” categories, but other parameters can affect whether or not it is practical to excavate rather than drill and blast. Moreover, as cutting technology improves, it is becoming practical to excavate materials today that we wouldn’t have considered twenty years ago. Examples of softer ores that can be excavated include coal, salt, and trona. Examples of harder ores that require drilling and blasting include limestone, copper, and lead. Some ores, for example, salt and potash, are exploited both ways. We will discuss the reasons for that in this lesson.

Every mining method, with the exception of solution mining, employs these unit operations. (We could force fit solution mining into this paradigm, but it would be a bit weird, so we’ll not do so. Besides, solution mining accounts for a very small amount of all mining.) The specific equipment chosen to implement each of the unit operations may vary by mining method, and even within methods there may be equipment and practices variation. In this Module, we’ll focus on the overarching principles, and we’ll take a look at the equipment that is commonly used.

There is one other category of common operations known as auxiliary operations. Auxiliary operations support the production cycle and are essential to it, and like the unit operations, they are repeated over and over again; and as with the unit operations, the specifics of the auxiliary operations will vary by mining method and the characteristics of the orebody. We’ll say a few things about the auxiliary operations in this Module, but save most of our discussion on these for when we look at the mining methods. The list of auxiliary operations can become quite long if you attempt to include every single activity that must occur during mining. We’re not going to try to do that, but a few are of special note.

Ground control and power are two auxiliary operations that are essential to every mining method. In underground mines, these two would be augmented with ventilation as an essential and major auxiliary operation. In surface mines, an argument could be made that reclamation would be an essential and major auxiliary operation. Others would argue that maintenance should be on the list of essential and major auxiliary operations. There are other auxiliary operations that are more specific to the method, such as preparing and placing backfill in mines employing the cut and fill method; or commodity, such as the explosion prevention activities in mines, regardless of method, that have explosive gas.

Taken together, the unit operations and auxiliary operations constitute the cycle of operations, which will be different among the different mining methods. Accordingly, we will discuss and document the cycle of operations that are inherent to each when we look at the individual methods in more detail.

See text above image
Figure 5.1 What goes into the Cycle of Operations
Credit: © Penn State University, is licensed under CC BY-NC-SA 4.0

In this Module, we’ll examine engineering concepts that apply to unit operations, which will then facilitate a more detailed analysis when we look at the specific mining methods, and we’ll identify the names and general characteristics of the equipment used for these operations. In the remainder of this lesson, I want to introduce you to the equipment used in the production cycle.