Rockfall occurs when rock blocks suddenly detach from a steep slope. Freeze-thaw cycles can cause rocks to fracture, lose their cohesive strength, and break loose. Debris flows or a rockfall can result in personal injury, property damage, and extensive traffic disruptions.
At GeoStabilization International®, our teams offer anchored mesh slope stabilization and rock bolt mitigation solutions to prevent these landslides from causing damage.
A federal agency made a rock cut during the road construction for its headquarters office access road in the early 1970’s. Although the road cut is nearly continuous in this area, episodic rock failures have occurred since its construction. GeoStabilization International® was asked to stabilize the failing rock slope.
The rock cut slope consisted of 980-linear feet of near vertical weathered schist and sandstone, of which some wedges have failed and blocked the roadway below, with the rock cut broken into a lower and upper section. The lower section ran the entire 980-linear feet, and the upper section ran another 280-linear feet. A v-ditch lined bench separated the upper and lower section. The average height of the sections was 35 feet, and the total estimated area of both sections was 45,000 square feet.
The exposed rock was systematically jointed and had very blocky characteristics. The rock blocks were generally little to moderately weathered, strong to very strong, and moderately hard to very hard. Weathering in the rock mass occurred mainly along discontinuity planes, where the rock was generally highly weathered to locally completely decomposed.
A team consisting of GeoStabilization technicians, a general contractor, and a consulting engineering firm conducted mechanical scaling consisting of a combination of a long reach and traditional excavators with scaling blanket attachments. Following the mechanical scaling process, GeoStabilization’s rockfall technicians hand-scaled the slope to ensure the removal of any remaining loose rock material. GeoStabilization’s rockfall engineers redesigned the planned 14-foot long spin-lock anchors solution in favor of 24-ft long post-tensioned SuperBolts™, which, due to their speedy installation, were installed at the same cost and in less time than the planned spin-lock anchors. The SuperBolts™ were installed throughout the rock face and used to anchor Maccaferri® B600 high-strength steel rockfall mesh. The project was completed safely, on time, within budget, and at a higher factor of safety than the original design.
GeoStabilization International® removes all loose rock from a cliff face during a rock scaling service to manage rockfalls. This service typically includes a geological survey utilizing aerial vehicles (UAVs) and 3D photogrammetry to determine the most effective methods for dislodging loose rock. Then, crews take steps to protect nearby infrastructures, such as public or private utilities and buildings.
Scaling starts at the top of each slope, then works down to the bottom. Certified technicians use ropes to access and remove loose rock structures.
GeoStabilization International® crews use mechanical methods and tools to scale loose rocks, including hand tools, pry bars, and inflatable airbags. Some cases require non-explosive demolition agents to remove boulders and other structures that can potentially break loose and fall.
GeoStabilization’s rockfall mitigation team responds to notification calls within 24 hours, mitigating the public’s risk of personal injury or property loss.
Installing an anchored mesh system is an effective method to stabilize rock or soil faces. This system consists of a high-strength wire mesh that attaches to fixed points using rock anchors or soil nails.
An anchored mesh system is suitable for small- or medium-sized slopes that regularly encounter low-magnitude rockfalls. Crews must first calculate the placement and anchor spacing of these slope retention systems according to the mass of the loose rock materials.
The anchored wired mesh systems offer various advantages, including minimal maintenance, not needing a catchment area, preventing slope erosion and mass wasting, and allowing vegetation growth and unconfined water draining.
A rock bolt installation can mitigate rockfalls on a smaller scale, and GeoStabilization International® often combines this solution with anchored wired mesh.
A rock bolt is an anchor screw utilized to secure potentially loose rock slabs to intact rock structures. For example, the roofs of mine, rail, and road tunnels typically feature these anchors to prevent rock falls due to moisture and vehicle vibrations. Another advantage is that rock bolts can prevent roadside rockfalls from mountain slopes.
A rock bolt installation is generally only effective in preventing low-magnitude rockfalls. Using rock bolts with netting or mesh mitigates the risk of large-scale rockfalls.
At GeoStabilization International®, our engineering and frontline teams have provided anchored mesh slope stabilization and rockfall control solutions for over 20 years. Contact us at 855.579.0536 to learn how our geohazard mitigation solutions can contribute to your geotechnical project. Our slope stabilization services are available throughout the United States, Canada, and Australasia.
If you are interested in a no-obligation site visit to determine if our services fit your geohazard mitigation needs, call us at 855-579-0536 or fill out our contact form.
