In the rugged terrain of the Canadian Rockies, infrastructure projects must contend with challenging geology, steep slopes, and environmental sensitivity. A recent project in a British Columbia coal mining community demonstrates how engineered geosynthetic systems can provide long-term stability while accommodating natural vegetation .
The Challenge: A Degrading Shale Slope
Nestled in the foothills of the Canadian Rockies, a coal mining community in British Columbia was dealing with an abundance of shale slopes that had formulated over time. One soft shale slope was degrading due to geomorphic processes, causing scour and erosion to the hillside .
This slope was located above a mechanically stabilized earth (MSE) wall that supports a new coal conveyor, making a long-term soil stabilization solution critical to the project. The initial plan, which relied on only topsoil and natural vegetation, proved insufficient due to the risks of snow loading and natural erosion .
The Solution: GEOWEB® Geocells with Non-Woven Geotextile
The project owner and TetraTech (consulting engineer) worked with Presto Geosystems and the Layfield Group to find a solution to the eroding hillside. A few complimentary project evaluations were completed on the slope by Presto Geosystems' engineering team to assess several different slope lengths and anchorages to compensate for snow loadings .
The project evaluations provided product recommendations based on the specific characteristics, structural values, and specifications from the site. Based on the results, the GEOWEB Geocells with exclusively designed ATRA® geocell accessories were selected as a long-term, cost-effective slope stabilization solution. The GEOWEB System maintains the slope angle while keeping granular material in place .
GEOWEB Geocells (GW30V4): Mid-sized cell, 4 inches deep panels
Non-woven geotextile separation layer: Placed along the sidehill cut slope area
ATRA® Tendon Clips: Integrated clips that "lock" with the GEOWEB cell wall for the most secure connection
Deadman anchor: Installed in a trench on top of the slope
Tendons: Connected from the deadman anchor through the geocell system
Installation Process
Partnering closely with TetraTech's Engineer of Record and Duz Cho Construction, Layfield Group forged a deployment plan that promised stability and resilience .
Step 1: Anchor Installation
The project installation began by digging a trench for a deadman pipe on top of the slope .
Step 2: Geotextile Placement
A non-woven geotextile separation layer was placed along the sidehill cut slope area using a man-lift. This geotextile provides separation between the underlying shale and the infill material, preventing fines migration and maintaining drainage .
Step 3: Geocell Deployment
After placing the geotextile sections, the GEOWEB Geocells were expanded down the 1.43H:1V cut slope. The tendons were tied to the deadman anchor on top of the slope .
Step 4: Securing the System
The integral ATRA Tendon Clips were tied to each tendon at every sixth GEOWEB cell. These clips "lock" with the GEOWEB cell wall for the most secure connection, and a looped tie-off assures that tendons stay bound to the device. The "locked with the cell" design also allows for easy preassembly off-slope—a huge time saver, especially on steeper slopes that are difficult to access .
Step 5: Backfilling
After the GEOWEB sections were expanded, the contractor backfilled the deadman crest area with on-site siltstone bedrock. They then continued to backfill the GEOWEB Geocells with topsoil, starting at the crest of the slope and working all the way down towards the toe .
The GEOWEB sections were slightly overfilled to allow for consolidation and compaction of the backfill as per the specifications, and the area was seeded for vegetation growth .
Key Installation Innovations
Layfield Group's on-site technical support was pivotal, guiding the contractor through best practices to ensure a safe and successful installation. The deployment was executed swiftly and without incident, thanks to meticulous planning and on-the-fly adjustments, including :
Pre-assembling the GEOWEB sections before deployment
Realigning the anchor trench for optimal effectiveness and ease of construction
Why the GEOWEB System Worked
The GEOWEB Geocell system provided several advantages for this challenging application :
Structural stability: The three-dimensional cellular structure confines infill material, preventing downslope movement and maintaining slope angle.
Load distribution: The system distributes stresses from snow loading and potential erosion events across a wider area.
Vegetation support: The geocells hold topsoil in place, allowing vegetation to establish and provide additional root reinforcement.
Flexibility: The system accommodates some settlement and movement without catastrophic failure.
Long-term durability: Geocells are engineered for decades of service life in demanding conditions.
The Role of Non-Woven Geotextile
The non-woven geotextile separation layer played a critical supporting role :
Prevents mixing between the underlying shale and the infill topsoil
Maintains drainage while retaining fine particles
Provides additional filtration for long-term slope stability
Project Conclusion
The GEOWEB Slope Protection System successfully addressed the eroding shale slope challenge, providing long-term stabilization for the critical infrastructure below. The combination of engineered geocells, proper anchoring, geotextile separation, and vegetation has created a stable, natural-appearing slope that will protect the coal conveyor for decades .
Lessons for Similar Projects
This case study offers valuable insights for projects facing similar challenges :
1. Engineering support matters: Complimentary project evaluations from suppliers like Presto Geosystems can optimize system design for site-specific conditions.
2. Integration is key: The combination of geocells, geotextiles, and proper anchoring creates a system greater than the sum of its parts.
3. Installation expertise counts: On-site technical support ensures proper deployment and maximizes system performance.
4. Vegetation integration works: Designing for vegetation from the start creates natural-appearing, sustainable solutions.
Conclusion
The British Columbia shale slope project demonstrates how geosynthetic systems can solve complex erosion challenges in demanding environments. By integrating GEOWEB Geocells with non-woven geotextile separation and proper anchoring, the project delivered long-term stability while supporting natural vegetation .
At HZ Geotextile, we offer geocell systems and complementary geotextiles for slope protection applications. Contact our team for assistance with your erosion control challenges.
