Introduction to Soil Mechanics

For civil engineers, soil plays a big part in the construction projects they are involved in be it a school, a large airport facility or even bridges and tunnels. This article discusses the reasons why civil engineers should study this developing branch in engineering.

Foundations

All foundations for any structure that a civil engineer constructs are bound to rest on the soil. The bigger the building or structure, the bigger its foundation and consequently the more important it is for a civil engineer to take into consideration the soil mechanics of the site. The foundation is where the load the structure bears is transferred hence understanding the soil is crucial to building a strong structure. Hard soil with sufficient strength allows an engineer to use shallow foundations, and the alternative is also true. Weak soil will need deep foundations to provide robust support for the structure being put up.

The Leaning Tower of Pisa, located in Italy is a good example of what can happen when a structure’s foundation is built without having the full appreciation of the soil mechanic forces at play. Deciding on what kind of foundation to use for a given structure will therefore depend on how a civil engineer applies his knowledge of soil mechanics to the project at hand in order to come up with the best solution.

Earthen Dams

Dams are a necessary part of today’s infrastructure. They help provide water for domestic use all year round, provide fishing grounds, act as scenic parks, support irrigation and are used to generate clean power when used for hydroelectric power generation. Dams are among the largest and consequently, some of the most expensive civil engineering projects in the modern world. Building them usually takes a lot of time and other resources such as manpower. Their construction requires that one comes up with a proper design to ensure that they can withstand the pressure from water and other elements in order to serve their purpose for a long time without any incidents.

The situation is even more serious when one considers that dams act as a barrier to flowing water that can alter soil properties. Dam failures can be catastrophic as witnessed when the Banqiao Dam in China failed after very heavy rainfall leading to a tragic number of deaths and great destruction of property. Understanding soil mechanics will ensure that any civil engineer carrying out such a project takes into consideration soil properties such as its density, permeability, and strength to come up with a solid structure.

Embankments

Embankments are usually constructed to raise the level of a road, railway or land above ground level. There are usually several reasons embankments are constructed. One of them is to raise the structure above flooding level. Anything that is built on the flat land is prone to flooding that can destroy the structure. Constructing the structure on an embankment is, therefore, a way of mitigating this. Embankments are also constructed to minimize or reduce the change in level due to a terrain’s profile. The embankment helps ensure the road/railway/structure is on the same level all through.

Embankments are usually constructed using soil as the main component. It provides the structural strength necessary to enable the structure to meet its purpose and is also economical. Being aware and able to factor things such as slope stability, consolidation and compaction of soil and the resulting settlement as well as aspects such as effects of soil seepage all contribute to successfully designing and constructing an embankment.

Canals or Other Retaining and Underground Structures

Canals are manmade waterways used for water distribution and transportation. The canals are designed to retain water and redirect it as intended. Any civil engineer, therefore, needs to carefully consider the properties of the soil on which the canal is to be constructed. Factors such as shear strength of the soil should be taken into consideration to ensure that the canal that is put up can withstand the force of water that flows through and minimize seepage as much as possible. The retaining walls, whether made of compacted soil or concrete, should also be designed accordingly having taken into consideration the soil mechanics that will be at play depending on the given surroundings soil type.

Today, most urban centers usually construct their infrastructure such as gas lines, electricity lines, drainage structures, subways and internet distribution cables underground. For large urban areas and cities, this can mean digging and tunneling through miles and miles of heterogeneous soil to be able to reach the millions of houses that make up the city. The need to understand soil mechanics in such civil engineering works is more pronounced for these underground projects. Being able to predict how the soil will behave and affect an underground pipeline or a subway is important so that the completed project can withstand the conditions underground and serve its purpose.

Excavations

The world today is heavily reliant on earth-extracted resources such as oil, gas, coal, metals and other minerals. The process of extracting these resources usually involves digging up and excavating soil. During excavation, one is bound to notice that soil can vary greatly depending on the depth and breadth even within a small region. Having a deep understanding of the types of soil and how they behave is, therefore, important in such excavation activities. Soil mechanics can help an engineer anticipate areas that may cave in or cause landslides during the resource extraction and come up with appropriate ways of preventing such disastrous incidents. Soil mechanics can also help civil engineers and geologists working at excavation sites identify areas with better prospects such as nodes that are capable of producing more of the resource being mined like copper, hence, directing the excavation activity as necessary.

Soil mechanics is a very important issue, especially for civil engineering purposes. Today, more research is being carried out in the field aided by better technology and new information is being discovered that will improve our knowledge in this discipline. To learn about the fundamentals of soil mechanics and the continuing research in the field, consider pursuing a master’s degree in civil engineering.

Sources

The Forgotten Legacy of the Banqiao Dam Collapse, International Rivers

Intro to Soil Mechanics: the what, why & how, California Institute of Technology