Most people think of construction as a vertical endeavor. But excavation—moving dirt, rock, and other material—is arguably one of the most important parts of any construction project.
The word excavatecomes from the Latin word excavare—which literally means to hollow out, like a cave.1 While most excavation projects don't involve digging any caves, excavating always includes moving earth, rock, and other surface material.
Nearly every vertical construction project starts with digging or excavating, and that's just the most visible construction work. Excavation is also necessary for all environmental restoration, mitigation, mining, exploration, heavy highway, bridge, and landfill projects.
During this stage of construction, backhoes, excavators, loaders, crushers, graders, draglines, and other heavy equipment may be used to remove material and prepare the site for building.
Before excavation begins, the excavation site must be surveyed and evaluated for environmental hazards and habitat requirements.
Next, the size and depth of the designated excavation area, according to the contractor's plans, must be clearly marked for the heavy equipment operators.
The primary pieces of heavy equipment used in excavation are the excavator and the dozer. On most construction projects, excavation will also require dump trucks, bulldozers, and wheel loaders to transport material around or away from the job site.
The following is a breakdown of the excavation process:
Excavation is used on almost every construction project. Residential foundations, commercial site preparation, man-made lakes, and mining sites require excavation. During this portion of construction, the earth's surface is dug up, rearranged, and smoothed out to prepare for vertical or sub-surface construction.
Like many parts of the construction process, excavation requires skill, experience, and attention to detail. Those working in excavation have to learn skills from reading the blueprints and operating heavy equipment to using special techniques and creativity when dealing with tricky soil conditions.
Moving dirt is a big job. The more dirt, the more costly the job and the more important it is to use time efficiently. Designing a project that saves money and time requires a thorough understanding of the types of excavation necessary for a given project.
It is helpful to think about excavation by classifying it according to two distinct features: excavation by material and by purpose.
Topsoil excavation is the removal of the immediately exposed layer of earth. This includes topsoil and vegetation like trees, bushes, and grasses.
Rock excavation is just what it sounds like—removing rock from a site. This type of excavation uses drilling and blasting because rock can come in layers that are several yards thick and boulders as big (or bigger) than cars. It requires hammer attachments, drills, or explosives to break up the rock so that it can be removed.
Muck excavation is the removal of excessively wet and undesirable soil. Muck is unstable because of its high water content and cannot usually be used to bear loads or create embankments. Muck can be dried out by spreading it over a large area and leaving it to dry or by stabilizing it with other material.
Earth excavation used to construct embankments and foundations removes the layer of soil immediately beneath the topsoil and on top of the rock layer. Earth is distinguished from rock by its capacity to be plowed, ripped, or broken apart into small enough pieces to be quickly loaded into hauling units and removed or incorporated into an embankment or foundation.
Unclassified is the catch-all category for any combination of the previous materials. When a job requires unclassified excavation, those performing the work must be prepared to move earth, regardless of what type of material is encountered.
Defining excavating by purpose is helpful for understanding the end goal of the job. Here are some of the most common ways of defining excavation by purpose.
Cut-and-fill excavation describes the removal of earth from one part of a job site to another and then utilizing that same material from the depression made by excavation to create embankments or slopes.
A trench is a narrow cut, cavity, or depression made on the earth's surface. Trenching excavation usually involves digging in a pre-set, narrow line that may require shoring to keep people on the worksite safe. Trenching is great for foundation footings, drainage, utilities, and other applications.
Basement excavation, or footing excavation, is where digging is done to create the foundation for a building. This type of excavation is usually done close to grade and as neatly as possible to cast concrete accurately and without forms. This type of excavation takes particular skill and firm soil.
Dredging involves the removal of underwater material, usually with the help of a dragline. A dredging project is done with the help of excavators, backhoes, and barges.
Everything from warehouses to skyscrapers starts down low, in the dirt. The quality of built structures that help societies to flourish begins with precision earthmoving. Excavating often goes unseen, but without excavation, we wouldn't be able to make anything that requires a level grade or a strong foundation.
Excavation is physical. Practical. Complex. It requires a thorough knowledge of how different soil types act and which heavy equipment should be used for moving material. This is a basic overview of what excavation means in the Dirt World, but excavation is an art that can take years to master.