After a sudden rockfall injured several motorists, the university wanted to alleviate any immediate danger and prevent a reoccurrence. Challenges to implementing remedial measures included limiting traffic stoppages on the busy roadway, bringing down loose boulders in a controlled manner and conducting drilling on near-vertical surfaces using rope-access techniques.

Workers installed a temporary rockfall catchment fence  on the mid-slope bench. They used specially modified drills to install rock bolts into the remaining large sandstone blocks. Anchor points were drilled behind the slope’s crest, and wagon drills were manipulated vertically on ropes, requiring constant communication between workers and support crews. When site constraints prevented drilling at designated bolt locations, expedited design reviews ensured that field changes did not compromise the stabilization effort. Fiber-reinforced shotcrete sprayed above, on and below the sandstone blocks created a seal against water intrusion and armored less durable layers beneath the overhangs. At the slope’s toe, a hybrid rockfall attenuator uses a high-tensile mesh to direct material to a safe area. To remove a large sandstone block located approximately halfway up the slope, the team inserted Autostem cartridges into predrilled holes. The cartridges released expanding gas to safely break the block into pieces. The process required a 20-minute closure of the roadway, the only traffic interruption during the effort.