As an engineer, builder or construction manager you need to be aware of the different types of excavation support systems used in deep foundation construction. This will help ensure that the foundations are properly supported during construction, and that the structure is stable and safe once it is completed. There are several different types of excavation support systems, and each has its own advantages and disadvantages.

In this blog post, we will discuss the most common types of excavation support systems and explain how they work. We will also outline the pros and cons of each system so that you can make an informed decision when choosing a system for your project.

Let’s take a look at these five excavation support systems:

Soldier piles and lagging
Steel sheet piling for support of excavation
Secant or tangent piles in deep foundation support
Soil nail walls as earth support systems
Grouting in earth retention

Soldier Piles and Lagging for Foundation Shoring.

As a piling & shoring contractor, one of the products we use are soldier piles. Soldier Piles are steel H piles that are vertically driven or drilled into the earth at regular intervals prior to excavation. As excavation progresses in stages, we add horizontal lagging in the form of timber, steel plate or precast concrete behind the flanges to create the Soldier Pile and Lagging Wall. Soldier pile retaining walls (aka a soldier pile wall) are constructed to prevent the lateral movement of soil.

They accomplish this through the use of steel beams and lagging. These walls are typically used where there is a sudden change in elevation, such as a steep embankment. Soldier piles are also used when an existing structure is close to the new excavation. In this situation, they help to support the existing structure while the new excavation is taking place. If you have a project that requires soldier piling, please don't hesitate to contact us. We would be happy to give you a free quote.

Pros & Cons of Soldier Pile Walls

Piling and shoring contractors are experts in soil mechanics and the construction of temporary and permanent retaining walls.

Pros

Soldier piles are fast to construct, versatile, and relatively inexpensive when compared to other systems. Lagging is the material that is placed between the soldier piles to create the actual wall. Common lagging materials include timber, precast concrete panels, or steel plating. Permanent transportation walls usually utilize precast concrete panels while temporary soldier pile walls in the US utilize timber lagging.

The major advantages of soldier pile walls are that they are:

fast to construct,
cheap,
versatile,
and easy to adjust in the field.

Cons

There are a number of reasons why soldier piling and lagging systems may not be the best choice for a retaining wall system, especially when compared to other options.

One of the primary disadvantages is that they are primarily limited to temporary construction applications.
Additionally, they cannot be used in high water table conditions without extensive dewatering, which can be costly and complicated.
Poor backfilling and associated ground losses can also result in significant surface settlements.
Soldier piling and lagging systems are also not as stiff as other retaining systems, which can lead to additional problems.
Finally, because only the flange of a soldier pile is embedded beneath subgrade, it is very difficult to control basal soil movements.

For all these reasons, it's important to consult with a piling & shoring contractor to determine the best solution for your project.

Contact Shore Systems Group, LLC today for more information for support of excavation and retaining wall construction.

Solider piles used to support foundation excavation in Northern New Jersey.

Soldier Piles As An Earth Retaining Systems.

Soldier pile and lagging walls are designed to resist earth pressure by utilizing both the piling system and the passive soil resistance. The soldier piling provides the moment resistance while the lagging wall transfers the lateral load to the piling system. The lagging wall is used to bridge and retain soil across the piles. The purpose of the lagging is to provide a soil plug that can be anchored into place and grouted at depths below the excavation.

The lagging wall itself does not provide any significant structural resistance other than its dead weight and the connection to the soldier piling. The primary advantage of using soldier piling and lagging walls is that they can be constructed rapidly with minimal disruption to adjacent properties. In addition, this type of retaining wall is very versatile and can be adapted to suit a variety of site conditions. As a result, they are an ideal choice for many commercial, industrial, and residential applications.

Steel Sheet Piling As An Excavation Support System

Sheet Piles support the excavations of underground parking garages, subway tunnels, and other large structures. The steel sheets are placed in a line along the perimeter of the excavation site. Sheet piling contractors drive, vibrate or hydraulically install the sheet piles into the ground. The interlocking edges of the sheet piles create a support system that prevents the soil from collapsing during excavations.

Sheet piling is also used to construct cofferdams, seawalls, and bulkheads. These water-resistant barriers prevent flooding and groundwater flow. Sheet piling is an essential support system for many large construction projects. They are used to retain earth or keep out water.

Types of Sheet Piling Commonly Used in Excavations

There are about 40 models or types of sheet pile made and used in the USA. Top manufacturers are Casteel, Shoreline, Nucor and Chaparral. All are in the Z shape. The lightest sheet piling is Shoreline’s LZ7 at 8.85 pounds per square foot, to the largest weight CZ148 by Casteel which weights 30.31 pounds per sq.ft.

CZ style from Casteel

LZ style by Shoreline

NSZ type from Shoreline

PZ piling by Nucor

SZ by Shoreline

Sheet Piling For Temporary Support

Sheet piling is a good temporary piling system for deep excavation because it can be installed before excavation begins. Sheet piles provide a shoring system that does not require any work during excavation, which is especially useful in excavations that need to go past the level of groundwater.

Sheet piling is also less expensive and easier to install than other types of systems. sheet piles are available in a variety of sizes and shapes. Sheet piling is an effective way to prevent soil erosion and protect the excavation site from weather damage.

Secant or Tangent Piles Uses in Foundation Support

Secant Piling

A secant pile wall is a shoring installation that uses overlapping (secant) piles to form structural or cutoff walls and achieve the required water tightness. The design can incorporate steel bar or beams for reinforcement and anchors can provide additional lateral support, if needed. Secant pile walls are often used as basement walls, retaining walls, cofferdams, and shear walls. They are also used to support earth backfill and provide shoring for excavation.

Secant piling is constructed by drilling overlapping holes and installing steel reinforcement. Concrete is then poured into the holes and allowed to harden. This forms a solid wall that is strong enough to support the weight of the earth behind it. Secant pile walls are an effective way to shore up excavations and provide support for backfill.

However, they are expensive and require a skilled shoring contractor to install them properly.

Tangent Piles

A shoring pile contractor will often use tangent piles to shore up an excavation site. Tangent piles are similar to secant piles, with the exception that instead of overlapping, the piles do not touch. While they do not offer the water-tightness of secant piles, they do provide a very robust shoring system in difficult conditions, particularly when tiebacks cannot be used due to site logistics and easement limitations.

In addition, tangent piles are easier to install than secant piles, which can save time and money on a shoring project. As a result, tangent piles are a popular choice for shoring contractors working in challenging conditions.

Soil Nail Walls As Earth Support

A soil nail wall is a shoring system used to support vertical excavations in a variety of soil conditions. Soil nail walls are typically constructed by a shoring contractor who "installs" small diameter grouted thread bars into the soil mass using an array of specialized equipment. The soil nails are then coupled with a shotcrete facing, which can be either permanent or temporary.

Soil nail walls are an efficient shoring system because they can be installed quickly and easily in limited access site conditions. In addition, cased and encased soil nails can be used in order to increase stability and load capacity. Hollow core soil nails are also sometimes used in order to improve the efficiency of the shoring system.

Finally, pressure and post grouting can be used to further increase the stability of the soil nail wall.

Grouting For Earth Retention

Permeation grouting (chemicla grouting) is a type of grouting that fills cracks or voids in soil and rock and permeates granular soils with flowable grouts to create a cemented mass. This process can be used to improve the strength and stability of soils, as well as to seal off water infiltration routes. In permeation grouting, a grout is injected into the soil through small holes drilled at regular intervals.

The grout then flows through the soil, filling any voids or cracks that it omes into contact with. As the grout sets, it forms a strong bond with the soil particles, creating a cemented mass that is less likely to be eroded by water or wind. This type of grouting can be used to improve the stability of slopes and embankments, as well as to seal off leaks in dams, canals, and other water-based structures.

Grouting as a soil stabilization system.

Chemical grouting is a process that helps to stabilize soil by injecting chemicals into the ground. This process can be used to improve the strength of the soil, bolster its rigidity, and reduce vibration. It can also be used to control water flow and limit ground movement. Chemical grouting is often used by earth retention contractors to help stabilize earth during and after the construction process. By injecting chemicals into the ground, they can help to ensure that the earth is able to support the weight of the structure and that it will not suffer from cracking or sinking.

Compaction Grouting

Compaction grouting, otherwise known as low-mobility grouting, is a ground improvement technique that improves the strength and stiffness of the ground by controlled, high-pressure injection of low-mobility cementitious grout. As the grout mass expands, the soil is displaced and compacted. The grout does not flow away from the injection zone. The result is a series of very stiff, bulbous grout columns surrounded by soil of increased density.

Compaction grouting is used for sinkhole repair, improving soil under new or existing structures, including the re-leveling of facilities. Improving collapsible soils, liquefaction mitigation, and general ground improvement and settlement control are all important uses for compaction grouting. This technique has been used extensively around the world to improve all sorts of soils in a variety of applications.

When done properly, compaction grouting can be a very effective way to improve the overall strength and stability of the ground.

Slurry Grouting

Slurry grouting is an earth shoring technique used to improve the characteristics of in-situ materials, such as gravel or bedrock. This grouting technique also reduces water seepage and enhances the soil's load-carrying abilities. The method involves the injection of neat cement grout mixed at various proportions into open-graded overburdened soils.

This earth shoring technique is used during temporary or permanent excavations or around existing below-ground infrastructure. Slurry grouting is an effective way to reduce water seepage, underpin structures, and improve the overall stability of the surrounding soil.

Permeation Grouting

Pressure grouting is a process in which microfine cement is used to permeate cracks and fissures in the soil. This produces a solidified mass that can support increased loads and fill voids in the ground. Permeation grouting is used to control water seepage, provide temporary and permanent underpinning of existing foundations, improve the bearing capacity of soils under existing foundations, and excavation shoring.

In situations where the cracks and fissures or the soils are too small to allow the slurry grout to infiltrate these spaces, pressure grouting with microfine cement can be an effective solution. A shoring systems company has extensive experience with this type of grouting and can provide you with the expert services you need to complete your project successfully.

Conclusion

Each of these shoring systems has its own benefits and drawbacks, so it’s important to consult with an excavation support specialist in order to choose the system that will work best for your project.

At Shore Systems Group, LLC, we have years of experience helping clients select the right shoring system for their needs. We offer a wide range of excavation support services, from soldier piles and lagging to soil nail walls and sheet piling, so you can be sure that we have the expertise to help you get the job done safely and efficiently.

Contact us today to learn more about our services or request a quote online.