Source: Equipment Radar
Excavation, or digging, is the process of removing material such as dirt, sand, gravel, and more, using either human-powered tools or machinery. It generally involves two key steps: breaking the surface and relocating the excavated material to a different spot. Excavation machinery, often referred to as diggers, are indispensable on most construction sites because they prepare the groundwork for new structures and foundations.
Typical tasks that require the use of diggers include:
- Creating trenches and laying foundations
- Digging holes for utility lines or building footings
- Mining operations
- Landscaping projects
- Road construction and maintenance
- Dredging rivers and harbors
- Grading and leveling land
- Tunneling through mountains or beneath urban areas
Among the most common applications of diggers are residential, commercial, and infrastructure construction. Buildings and roads typically require a stable and level surface to ensure structural integrity, and natural terrain is rarely ideal. Therefore, construction crews rely heavily on excavation equipment to transform the landscape into a suitable foundation for construction.
Types of Digging Machines
There are numerous types of construction machinery designed for excavation purposes. The term "digger" broadly refers to any equipment capable of digging, including excavators, mini-excavators, mining shovels, draglines, augers, trenchers, scrapers, backhoe loaders, bulldozers, skid-steer loaders, motor graders, and crawler loaders. The most popular types are usually excavators and mini-excavators.
Excavators
Excavators are large, versatile pieces of machinery widely used across various job sites. They are typically mounted on tracks or wheels, with tracks being the more common choice due to their superior performance on uneven surfaces. An excavator is equipped with a hydraulic arm featuring a bucket attachment, which is controlled from a rotating cab. Operators sit inside the cab and control the arm, bucket, and movement of the machine. The standard attachment for excavators is a bucket, used for digging, scooping, and moving materials. Excavators are incredibly adaptable and can be fitted with a range of attachments depending on the task at hand.
Source: Caterpillar.com
Mini-Excavators
Mini-excavators are scaled-down versions of traditional excavators, making them more portable and easier to maneuver. These machines typically generate up to 70 horsepower and have a maximum operating weight of around 2,000 pounds. Mini-excavators are particularly well-suited for urban environments, where their compact size allows them to navigate tight spaces. Their digging depth usually ranges from 5 to 16 feet.
Source: Caterpillar.com
Mining Shovels
Mining shovels are specialized machines designed to handle massive quantities of overburden and ore. These shovels are costly and are primarily used in open-pit mining operations. Caterpillar’s largest mining shovels have a payload capacity of 120 tons, a dipper capacity exceeding 80 cubic yards, and a total weight of over three million pounds.
Source: Caterpillar.com
Dragline Excavators
Dragline excavators, also known simply as "draglines," are among the largest machines ever built. These machines are expensive, often costing tens of millions of dollars, and are typically found at large-scale mining operations. Draglines have an operational lifespan of several decades. A dragline bucket system consists of a large bucket suspended from a boom using wire ropes, with the bucket being moved using multiple ropes and chains.
Draglines are the largest digging machines in existence. Caterpillar's largest dragline, the Caterpillar 8750 Dragline, can move over 150 cubic yards of material, with its boom extending over 400 feet. This machine weighs approximately 16 million pounds.
Source: Caterpillar.com
Bulldozers
Bulldozers, also called "dozers," are heavy-duty machines commonly used for large-scale earthmoving projects. They are extremely powerful and capable of shifting vast amounts of material. Dozers typically feature a wide, flat blade at the front that is manipulated using hydraulics. They are frequently used in road construction and projects requiring significant dirt removal. The vast majority of dozers are equipped with tracks for enhanced stability and traction.
Source: Caterpillar.com
Trenchers
Trenchers are specifically designed to dig trenches, as their name suggests. They carve narrow, elongated holes, typically for burying cables, pipes, and utilities. Trenchers function similarly to a chain saw, but instead of cutting wood, they cut through the earth.
Trenchers come in various sizes and types, ranging from small walk-behind models to large trenching machines capable of cutting through asphalt and other tough surfaces. They often include a conveyor system to transfer excavated material away from the digging area. The digging depth of a trencher is usually determined by the length of the blade.
Source: DitchWitch.com
Skid-Steer Loaders
Skid-steer loaders are highly versatile machines used extensively in construction due to their compact size, affordability, and efficiency. They are capable of maneuvering in confined spaces, making them ideal for urban environments. Available in both tracked and wheeled versions, skid-steer loaders support a wide range of attachments, enabling them to perform diverse tasks like digging, compacting, drilling, grappling, snow plowing, jackhammering, material handling, and more.
Source: Caterpillar.com
Motor Graders
Motor graders are heavy machinery used for grading and moving small volumes of dirt. They feature a long blade underneath the machine that can be adjusted to create a flat and smooth surface. Some motor graders are equipped with a second blade located ahead of the front axle.
Motor graders are commonly used in road construction and site preparation, such as during the development of new housing communities. Besides creating flat surfaces, motor graders can also form sloped surfaces and shallow V-shaped drainage ditches.
Source: Caterpillar.com
Backhoe Loaders
Backhoe loaders, often referred to simply as "backhoes," combine a shovel in the front and a bucket in the rear. The bucket operates much like an excavator arm and is used for digging. Backhoe loaders vary in size from medium to compact, making them suitable for working in smaller spaces. They are primarily used for digging trenches, holes, and moving materials. Most backhoes run on wheels, making them better suited for urban areas and flat terrains.
Source: Caterpillar.com
Advanced Digging Technologies
Surprisingly, rework is a significant factor affecting construction project profitability. Errors in excavation can lead to increased labor hours, higher material costs, and project delays. For instance, a misaligned foundation could necessitate costly corrections and project delays.
Precise excavation can be challenging, especially when operators rely solely on visual estimation. Determining the difference between a 0-degree grade and a 2-degree grade can be difficult, particularly when working at great depths where visibility and space are limited.
Trimble, a pioneer in precision agriculture and construction equipment, has developed innovative technology solutions to automate excavation and grade control for excavators, bulldozers, compactors, motor graders, and more. Trimble's technology leverages computer-aided design (CAD), sensors, and GPS to plan, control, and monitor excavation activities at construction sites.
Trimble's grade control features:
- Minimize over-cutting and under-cutting
- Enhance efficiency and accuracy for less-experienced operators
- Achieve precise finished grades with fewer passes, eliminating the need for manual staking or bluetops
- Track project progress using machine data to reduce reliance on surveyors and grade inspectors
- Identify over-compacted or under-compacted areas or subsurface weak points
- Improve compaction efficiency by achieving target pass counts more accurately
Trimble's Grade Control on Excavators
Source: Trimble.com
Common Methods for Digging Holes
Safety Considerations in Excavation
Excavation poses serious risks to all workers involved, with cave-ins being the most dangerous hazard. Cave-ins are more likely to result in fatalities compared to other excavation accidents. One cubic yard of soil can weigh as much as a car, potentially burying, crushing, or suffocating workers.
Extra caution should be exercised when digging deep trenches or near the edges of excavations. The weight of the machinery can cause the ground to weaken and collapse. Always pay attention to your surroundings, assess soil compaction levels, and consider relative depths.
Soil Classification
According to excavation standards, workers must classify soil and rock deposits as follows:
- Stable Rock: Naturally occurring solid mineral matter that can be excavated with vertical sides and remains intact while exposed.
- Type A Soil: Cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) (144 kPa) or greater. Examples include clay, silty clay, and clay loam.
- Type B Soil: Includes cohesive soil with an unconfined compressive strength greater than 0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa), and granular cohesionless soils. Examples include angular gravel, crushed rock, silt, silt loam, sandy loam, and in some cases, silty clay loam and sandy clay loam.
- Type C Soil: Cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kPa) or less, granular soils. Examples include granular soils (including gravel, sand, and loamy sand), submerged soil or soil from which water is freely seeping, submerged rock that is not stable, or material in a sloped, layered system.
Pre-Digging Inspections
Before beginning excavation, it is crucial to inspect the area for buried obstacles. The free hotline 811 can assist in identifying underground utilities.
Items to look for include:
- Power lines
- Gas lines
- Water lines
- Fiber-optic lines
- Underground tunnels or roads
- Archaeological sites (protected)
Additionally, it’s important to know the approximate depth of your local water table. Ground conditions can change rapidly once the water table is reached.
Preventing Cave-Ins
OSHA generally requires employers to protect workers from cave-ins by:
- Sloping and benching the sides of the excavation;
- Supporting the sides of the excavation; or
- Placing a shield between the side of the excavation and the work area.
Resources
Excavation Safety: OSHA Trench & Excavation Safety
Monster Trench Digging Machine
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