Soil Anchors: Overview, History, Components, Applications

A soil anchor, which is made up of a steel tendon (also known as strands or bars), is a device that is used for grouting into soil or rock. Usually, soil anchors are grouted into the soil after a hole in the same has been drilled. Soil anchors are also referred to as ‘Earth Anchors’ whose purpose is to support constructions and are used in the maintenance and construction of Geotechnical applications.

Other names of soil anchors include mechanical anchors, percussion-driven earth anchors, or ground anchors. One of these anchors’ features is that they run spirally when being grouted into the rock or earth, and they, once drilled, hold, restrain, or support the buildings—or structures, or engineering slops. The soil anchors come in different shapes and sizes; they could be 70 meters long and usually have a capacity of 3,000 kN.

TL;DR — A ground anchor is a structural element installed in rock, ground, or soil to support walls, structures, or guyed towers, stabilise landslides, or sometimes used in sporting activities. These anchors are installed in grout-filled drill holes and used to transit tensile into the soil or rock.

Soil Anchors — Overview

Before we delve into detailed insights, let us go over the overview of ground anchors:

History

The first use of soil anchor dates back to the ‘90s. The first earth anchor was invented by an American businessman, Albert Bishop Chance. Albert got the inspiration or idea to make an earth anchor when his company’s telephone poles were knocked down by a storm. To remember his contribution, Centralia—a town in Pennsylvania—organises an annual ‘Anchor Day’ festival.

Components of Ground Anchor

A soil anchor may have different components depending upon its usage for a specific project; however, the essential components of a ground anchor include the following:

• Bond length
• stressing length
• Anchor head

Take a look to understand the working of a ground anchor:

Figure: Components of Ground Anchor

Applications of Soil Anchors

We can see active usage of ground anchors are used in civil engineering, and construction; these anchors are used in a variety of areas—to retain highway walls, stabilise slopes and landslides, tiedown structures, etc. 

• Highway retaining walls: These types of ground anchors are used to widen the roadway, construct depressed roadways, and also for roadway realignments. The primary purpose of such anchors is to align two or more roadway axes—i.e., for grade separation. 
• Landslide and slope stabilisation: Another advantage of using soil anchor is stabilising the slopes and landslides. This is beneficial because these anchors can be used with concrete blocks, horizontal beams, or walls easily. The purpose is to provide a large force to help stabilise the groundmass, especially where the surface is slippery. 
• Tiedown structures: Permanent earth anchors can also be utilised to offer resistance to vertical uplift forces caused by hydrostatic or overturning forces. There lie many advantages to using ground anchors in tiedown structures. The concrete volume can quickly be diminished compared to a dead weight slab, and dewatering can be brought down.

Earth Anchors — Other Applications

Earth anchors are also widely used to keep different types of structures in place. These anchors can also be used for:

• Retaining walls
• Supporting the structures or buildings temporarily or permanently, and sometimes to support outdoor stages, such as circus tents
• Sporting activities, abseiling or slacklining
• Anchoring the small aircraft
• Tethering floating jetty (pier), pipelines or marine structures
• Keeping guyed masts in place and firm
• Anchoring transmission pole (telegraph post)

Installation of Ground Anchors

Before using an earth anchor, one must fully understand the anchor installation in detail to avoid any injuries and ensure the firmness and stability of the project. It is recommended that one runs a deep analysis of the site where it is supposed to be installed, apart from determining the soil load resistance. Every aspect needs to be closely inspected, including soil strength, corrosivity, and moisture content. 

Therefore, the installation process may vary depending on the soil moisture content or composition. The soil anchors are generally driven into the ground using a drive rod, and a heavy-duty tool called a pile driver. If the soil is denser, pilot holes might be required for installation. Once the driver anchor is installed, the driver rod is taken out, and the anchor is load-locked. Only hand tools are needed if the installation is for a lighter anchor. 

Deadman — Off-road Anchor

Deadman is one of the best anchoring systems that does not require a lot of equipment to be installed. It is one of the simplest ground anchors that can be used in different ways —  it can be used in sand, wrapped around a tree, or even used around a little rock. If one gets stuck, this particular anchor can help recover from any situation quickly. It is space-efficient, budget-friendly, does not weigh much, and is super easy to use. Also, the recovery of this anchor is straightforward.

We hope that this comprehensive article on ‘Soil Anchors’ has been assistive and provided you insights into the purpose, types, and how different anchors work. If you still have queries or would like to provide feedback, please feel to reach out to us.

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