A Soft Introduction to Rock Mechanics

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A Soft Introduction to Rock Mechanics

Early in our lives, during our first foray into the sciences, we learn the basics of geology. For some of us, that’s enough to start a lifelong fascination with the way the earth is formed, both above and under the ground. The study of rock mechanics is builds upon that knowledge with an understanding of what happens to rock formations under various conditions.

What is rock mechanics?

The Rock Mechanics Committee of the American National Academy of Science defines rock mechanics as “the theoretical and applied science of the mechanical behavior of rock. It is that branch of mechanics concerned with the response of rock to the force fields of its physical environment.”

It is field of study that overlaps into other sciences such as geology, soil mechanics, and geophysics. The fundamentals of rock mechanics include rock behavior, rock mass response, flow, chemistry, and coupled behavior. Some of these, such as rock mass response, can be simulated in a laboratory or studied through theoretical modeling of field-based data.

 

How do rocks become deformed?

When rocks are under stress, they can become deformed by fracturing. There are three types of stress that can cause deformation. These include stretching (tensional stress), compression (compressional stress), and slippage (shear stress). Different types of rocks respond to stressors in different ways.

Clay-based formations, for example, have a high degree of elasticity and can be reshaped under pressure without breaking apart. On the other hand, rocks such as quartz and feldspar are extremely brittle and can easily fracture when stressed.

Brittle fractures are explained through The Griffith Theory, which suggests that inherent cracks in the rock formation, when put under pressure, can result in a phenomenon called “rockburst.” This is an occurrence characteristic of excavation sites and in instances of severe compressional stress.

What skill sets apply to the study of rock mechanics?

There are several competencies that come into play in rock mechanics. Some of these include lab testing, field testing, risk analysis, site management, equipment development, numerical modeling, and information technology. Current research into rock mechanics utilizes a combination of skill sets to advance the study of:

  • Effect of time and fluids on rock formations.
  • Static and dynamic behavior of rocks at the crystal level.
  • Long-term behavior of tunnels and other underground structures.
  • Advanced simulation methodologies using parallel computing.
  • Alternative measurement strategies for acoustic emissions, magnetic fields, and more.
  • Improved digital image techniques for better pattern recognition.
  • Deeper exploration into fault zones, ocean foundations, and outer space.
  • Predictability of earthquake triggers and similar geological phenomenon.

What industries utilize rock mechanics?

There are a number of industries that employ engineers with knowledge of rock mechanics. The mining, petroleum and construction industries are at the top of the list. Construction has multiple applications in infrastructure, tunneling, irrigation, dam building, and more. It is expected that demand for rock mechanics specialists will increase due to global trends such as:

  • Demand for materials found in hard-to-mine locations.
  • Growth in infrastructure and hydropower construction in developing countries.
  • The need to secure unsafe rock formations in populated areas.
  • Investment in geothermal energy and hydrocarbons storage.

It’s not hard to understand the depth of importance of rock mechanics as an essential part of achieving success in a variety of civil engineering career areas including transportation, wastewater, underground construction and more.

 

Sources

http://www.rocscience.com/hoek/references/H1966a.pdf http://education-portal.com/academy/lesson/rock-deformation-definition-causes-stages-byproducts.html#lesson http://isrm.net/fotos/editor2/nl15/ricardoresende_future_for_erm.pdf
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