To prevent a structure from collapse, there has to be some kind of support, shoring usually provides this support. The most common shoring technique that we encountered during the early stage of construction is an excavation. Shoring is important in preventing a project mishap due to the retained soil overturning in an excavation. It is often the go-to option when 1.20 meters or more excavation support is needed. Although it depends on the soil type.
However, shoring is not only about retaining excavation soil. In fact, it is completely different from an excavation retaining wall. The sole purpose of a retaining wall is to retain soil during excavation. Whereas, for a structural engineer, it is way more than that.
For a structural engineer, it is important that you decide on what type of is necessary for a construction project, as early as the beginning of the design stage. This article features 5 common types of shoring and their uses. But before we dive right in, let’s discuss what shoring means.
What is Shoring?
Shoring refers to constructing a temporary structure that would serve as lateral support to an unstable structure. Here are some situations for the use of shoring:
- Fixing bulged out walls
- When walls crack due to unequal settlement of the foundation and repairs are to be carried out to the cracked wall
- Pulling down an adjacent structure
- Making openings in a wall or enlarging one.
1). H or I-Beam Shoring
The first on this list of common shoring types is the H or I-Beam Shoring. Another name for this shoring type is soldier pile walls. Depending on the soil type, you can either drive prefabricated steel I or H sections into the ground by first drilling the soil or vibrate directly into the ground without having to drill the soil first.
To construct the complete shoring wall, concrete panels are pre-cast and installed between the steel beams already in the soil.
The use of this type of shoring ranges from supporting excavation with a depth between 1.2 meters to that of a depth of 5 meters. However, it can exceed 5 meters, as long as it’s design accounts for the surcharge load along its perimeter.
2). Secant Pile Shoring
The next type of shoring on this list is the Secant Pile Shoring. Its construction involves the intersection of two piles combination, a “reinforced” or “secondary” and an “un-reinforced” or “primary” pile. Forming a continuous wall by interlocking each other.
For cases where there are no rooms for open excavation, secant pile shoring is the best option. Additionally, the absence of space maybe because of the proximity of an existing structure. The secant pile shoring type is usually used for this case. However, the design must take into consideration the surcharge load due to the structure of close proximity.
3). Contiguous Pile Shoring
The Contiguous Pile shoring, also known as Tangent Pile shoring is a very useful shoring type. It consists of piles, tightly spaced, and the name tangent pile shoring comes from the fact that the piles lie tangent to each other.
For clay soils or areas where water is not so important or areas of very minimal water pressure, Contiguous Pile shoring is usually recommended. As it can help retain dry granular material. However, in water-bearing granular soil, this type of shoring will allow water seepage through the gap in the piles.
Grouting the gaps in the pile, forming a watertight wall, can prevent the water seepage. Additionally, Contiguous Pile shoring is not suited for a high groundwater table, especially without dewatering works.
4). Sheet Piles
The next shoring type on this list is the Sheet Piles. Its construction is similar to that of soldier piles. A Vibro hammer is used to drive a prefabricated steel section (Z or U) into the ground. The complete wall results from the connection of the sheet piles.
In addition to retaining soil to soil excavation, this shoring type serves as a good option when there is a need for excavation isolation from a water body (creek. Pond or sea-side). It is a common fit in the construction of ports and harbors.
5). Diaphragm Walls
Diaphragm walls come into play when the above mentioned shoring types do not fit for the excavation depth. Its construction is reinforced concrete. Diaphragm walls are flexible as its design takes into consideration the load that needs to be resisted.
Basically, for deep excavations like basements and tunnels, this is a good option.
Although there are other shoring wall types, the above are most common in construction.