Rock anchorage: how to install screw piles on rocky ground
When planning a construction project, discovering rock in the ground can be a challenge… but not an insurmountable one! At Pro Post Foundations, we have the experience and techniques to deal with all situations, whether it’s a small annoying rock or a site composed entirely of rock.
In this article, we explain how to detect the presence of rock, what parameters influence the installation method and what solutions are appropriate for each situation.
How can you detect the presence of rock beneath the surface?
Before installating, our installers will determine whether the ground contains rock or not.
During the first feet of the helical pile installation, unusual resistance is …
Resistance test during screwing
At the start of the installation, unusual resistance is quickly detected, indicating the presence of a solid obstacle.
Mechanical probing
Using a rod or a drill bit to probe the bedrock or the rock’s depth before installation
Geotechnical analysis
In more complex projects, geotechnical analyses are performed by professionals where ground samples are analyzed. Those tests provide our engineers withthe complete soil information and among them is nature of soil/rock and depth.
Parameters to consider : size and depth
Two main factors determine how we install screw pile foundations :
1. The size of the rock : is it a small obstacle or a large rock mass?
2. The depth : is the rock close to the surface or deeper?
These factors guide the choice of installation technique and the adjustments needed to guarantee the foundation will be solid.
Scenario 1
Small rock in the ground
In this case, our installers simply use a pivoting technique :
The pile is tilted slightly to bypass the rock, then returned to its intended axis.
This method allows the obstacle to be avoided while maintaining the required load-bearing capacity.
Scenario 2
Entirely rocky terrain
When the project is located on a terrain where rock occupies the entire surface or a large part of the subsoil, we use a technique developed by Pro Post Foundations :
- Use of a pneumatic percussion drill to drill through the core and perform core drill anchoring.
- The full diameter of the tube is inserted inside the hole which was drilled at a determined depth by a licensed engineer.
- Securing with a high-strength anchoring product to ensure long-term stability.
This method allows us to create a durable foundation even where it would be impossible to screw in a conventional pile.
Scenario 3
Single large rock underground
When a large rock is detected at depth, two options are considered :
-
If the rock is very large and has an impressive thickness, it provides sufficient bearing capacity to support the load. We can therefore anchor the pile to the rock.
- Excavate and remove the rock, when its position or stability does not allow for secure anchoring.
The choice is always made in collaboration with the engineering team, which evaluates the best solution for the project.
In short
Whether it’s a small rock, rock-filled soil, or a massive stone hidden beneath the surface, there’s always a solution for installing your screw piles safely and durably. Our expertise and specialized tools enable us to meet this challenge in all conditions.
Tell us about your project !
Contact your installer for an assessment and find out how we can anchor your foundations, even on rocky ground : https://propostfoundations.com/installer/