Foundation Repair Services helped to create a highly effective solution to stabilizing a boulder field that supported a parking deck in Boone, NC. Implementation of the SPIDER rock protection system allowed the parking deck to become operational once again.
Stabilization & Tensioning of Loose Rock Boulders
Foundation Repair Services has been providing the Western Carolina’s with slope and rock stabilization as well as landslide recovery services since 2004. Solving complex problems and thinking outside the box is our specialty and when it comes to geotechnical and structural foundation issues, we provide proven permanent solutions.
December 2011 – An Introduction
We were contacted by a structural engineering firm based out of Hickory, NC regarding a potential foundation issue with condominium’s parking deck in Boone, NC. The parking deck was largely supported by a boulder field that had a high risk of failure (falling apart). If the boulders became loose, there was a major risk for them to take out the support pillars, causing irreparable damage.
The Foundation Repair Services team, along with the structural engineering firm and a local construction company, found a highly [and cost] effective solution to stabilizing the boulder field, providing a permanent and solid foundation system. The SPIDER Rock protection system (SPIDER net) was chosen to stabilize the boulder field, allowing the parking deck to become operational once again.
Installing the Rock Protection System (SPIDER net)
After careful consideration and shuffling through many proven [yet expensive] foundation and slope stabilization techniques, it was determined that Geobrugg’s SPIDER spiral rope net was the correct solution and permanent fix.
These steps summarize the progress to stabilize the upper section of the boulder wall:
- Excavating 8 foot hole above the boulder field
- Driving Titan 30/16 bars into the bedrock at an angle, stubbed out
- The boulder wall was cored through so extensions could be secured to the Titan bars
- Titan bars were secured up against 15 inch channel whalers and bearing plates
Stabilizing the lower section of the boulder wall:
- Built an access road to the inaccessible lower portion of the boulder wall
- Began drilling for a row whaler anchor points that would secure the bottom portion of the SPIDER spiral rope net
- The next step was to drape the SPIDER net over the boulder rock face
- Drilled in anchors on the sides and through the middle portion of the boulder field, further securing the SPIDER net
Final stages of installing the SPIDER net:
- Spike plates were attached and secured to the SPIDER net
- A boundary rope was utilized around the perimeter of the SPIDER net
- Spike plates were tightened to apply torque against the net, which stabilized and secured the entire system
* In total, approx. 50 Titan 30/16/ 40/20 hollow bar injection anchors were used during this installation.
Additional Security and Stabilization Methods
To ensure longevity and a permanent stabilization of the parking deck, 1 inch diameter rods were drilled and epoxied through each (3 in total) of the parking deck’s support columns. To further strength the columns, a sag rod was installed to perpendicular to the parking deck.
Finishing and Final Touches
After the structural and foundation security aspect of the project was completed, brick pavers were placed and laid. Furthermore, a rubber membrane above the precast deck side and setting materials were installed to complete the job.
Fresh landscaping and mulch was added adjacent to the storm water junction boxes and temporary access road (leading below the parking deck).
The final step was to lay the matching veneer walls (stone) around the new water drain lines.
From start to finish, the project lasted approximately five weeks. Upon completion, the condemned parking deck was once again usable.
Earthquake (the test)
Eight months later, on August 23rd, 2011 at 1:51pm EST a 5.8 magnitude Earthquake struck approx. 40 miles Northwest of Richmond, VA. Tremors and seismic movement were felt shortly after in Boone, NC at the parking deck. Coincidentally, a few installation contractors were standing on the parking deck during this time. The SPIDER net system was strong AND flexible enough to withstand the tremors and aftershocks to keep the parking deck and all its occupants stable and secure.
This 5.8 earthquake was a true test of durability and security.