Soldier pile and lagging walls are great at resisting lateral earth pressure, especially when they incorporate precast lagging panels. A well-built retaining wall that uses these panels can continue to do its job for decades (or even an entire century).
But like any other construction project, retaining walls can run into serious issues along the way. To reduce RFIs and avoid problems during your installation process, you’ll need to think carefully about your precast concrete lagging panel specifications.
What are Soldier Pile Walls?
While soldier pile and lagging walls aren’t the only type of retaining wall in use today, they are a very popular choice in this category. These walls consist of regularly-spaced steel beams (AKA “soldier piles”), which are connected by timber or precast concrete lagging panels.
The service life you need from the soldier pile wall systems will help you decide which materials to use in this project. In temporary retaining walls, timber lagging panels might be enough to get the job done.
However, precast concrete is a much better choice for permanent retaining wall projects – the National Precast Concrete Association has stated precast concrete can last up to 100 years. Precast lagging panels also deliver benefits related to installation speed, quality control, and visual appeal.
The Basics of Lagging Panel Sizing
One of the most important things to specify while ordering lagging wall panels is the size of these components. As part of this, you should include information on your:
- Span between soldier piles. This is simply the amount of space between the steel beams in your retaining wall – that is, the length your lagging panels need to cover.
- Panel thickness. The thickness of lagging panels matters, too. With that in mind, be sure to explain where you plan to install your retaining wall and ask what panel thickness is right for your needs.
- Joints. Your lagging panels should connect seamlessly to your soldier pile walls, and sharing information about the joints you need can help.
How Should You Reinforce Lagging Panels?
While thinking about reinforcement for your lagging panels, be sure to consider factors like:
- Crack control. Even small cracks in concrete panels can get much worse over time. Fortunately, reinforcement can lower the risk of this happening.
- Lifting points. You’ll also need to make sure your panels can be lifted into place by heavy equipment without damage. Because of that, these panels should include lifting points.
- Edge durability. Spalling and other problems on concrete panels often start at these panels’ edges, so your reinforcement should take that into account.
Specifying Retaining Wall Tolerances
Retaining walls are somewhat flexible by nature. These walls are designed to handle a certain level of variation over the course of their lifespans.
Still, that doesn’t mean you should leave your retaining wall’s future up to chance. Instead, your lagging panel specifications should include specific tolerances for:
- Pile spacing variability
- Panel bearing
- Backfill contact
The Importance of Drainage in Retaining Walls
If you’re an engineer working on a retaining wall project, taking drainage seriously is a must. The soil that retaining walls hold back absorbs water, resulting in hydrostatic pressure if that water can’t escape. A lack of drainage built into your design plans for the project can also cause soil to migrate behind retaining walls and around their sides.
Because of that, you’ll need to put some serious thought into your new retaining wall’s drainage strategy. As part of this, your wall should include weep holes, which will allow built-up water to escape before it can cause problems.
Understanding Lagging Panel Handling and Logistics
By definition, precast concrete panels aren’t manufactured on-site, so you’ll need to know how you’ll get them from Point A to Point B. Some factors worth considering as part of this process include:
- Weight. Precast concrete panels are very heavy, which can make transportation difficult.
- Staging. Because of the size of precast lagging panels, you’ll need a large staging area if you plan to store these panels on-site for any significant amount of time.
- Site access. Sometimes, you won’t be able to get heavy equipment onto a job site due to access constraints. While you may be able to use smaller equipment in this situation, it’s always wise to think ahead.
- Damage prevention. Concrete is a durable material, but it isn’t impervious to damage. If you’re responsible for transporting your lagging panels, you’ll need to take steps to protect them along the way.
Luckily, you don’t have to tackle these issues on your own while planning a retaining wall project. If you get precast lagging panels from American Precast Concrete Inc., we’ll help you with panel storage, delivery, and (at your request) installation coordination.
Preventing Common Failures in Lagging Panels
Despite its reliability, precast concrete isn’t always free of problems. If you aren’t careful, your concrete lagging panels could run into issues like:
Spalling
When concrete is forced to deal with installation problems or the elements, it can develop surface spalling. In this situation, a concrete surface begins to flake, chip, or pit.
If your concrete lagging panels have started to spall, the only permanent solution is to replace them. However, cleaning/sealing your concrete and keeping up on other lagging panel maintenance tasks can reduce this risk.
Misfit
Precast lagging panels should bridge the gaps between a retaining wall’s soldier piles. When the sizing of these panels is slightly off, your retaining wall may have trouble functioning as intended.
The more precise your precast concrete panels are, the better. To get lagging panels you can trust, you’ll need to find a truly reliable precast concrete company and give them as many details as possible about your retaining wall project.
Rotation
Retaining walls don’t stay static throughout their entire service lives. Over time, the lateral earth pressure these walls resist will lead to some amount of displacement. But even though a few degrees of wall rotation is normal, excessive rotation could put a wall’s structural integrity at risk.
The key to keeping this issue under control is to include a setback as part of your retaining wall project. The soil you build your retaining wall in also matters – soils containing high levels of clay and silt can result in higher rotation levels than you might expect.
Voids
When the soil behind a retaining wall erodes, the resulting space is known as a “void.” Since this soil plays a key role in supporting your wall, this situation could put this structure’s integrity at risk.
Water build-up can contribute to soil erosion, so prioritizing drainage is a great way to lower your risk of voids. In addition to weep holes, you’ll want to think about backfilling your wall (that is, placing gravel or another material behind your wall to improve drainage) and installing a footing drain (a drain at the base of the wall that redirects water away from the structure).
Get the Right Precast Panels for Your Project
When you want to get the most out of your new retaining wall, you’ll need clear specifications for your precast lagging panels – and a company you can trust to meet these requirements. American Precast Concrete Inc. has been hard at work delivering precast concrete products since 1985, and we take pride in selling exceptional products at reasonable prices. If you’re ready to get started, ask us for a spec sheet and typical details package!