In the Mid-Atlantic Region of the United States a rockslide occurred that presented a variety of problems for the state’s Department of Transportation (DOT). The rockslide caused massive boulders to obstruct both lanes of travel on a local state road. To alleviate the emergency situation, the DOT hired GeoStabilization International® to mitigate the rockfall with an innovative slope stabilization system that could be completed in a safe and efficient manner.
Due to the active nature of the rockslide, special safety precautions had to be enforced to protect the GeoStabilization and DOT team members. The work was completed from each end and then progressed to the middle of the unstable area. Each phase of the stabilization had to be completed in sequence before crews could work below the rock slope.
The cause of the rockslide was a highly weathered layer of rock that became unstable. As water entered the cracks in the unstable rock formation, large sections of the rock began to fall. The failed layer left a void in the rock slope that was previously providing support to the entire rock mass above.
GeoStabilization’s crews quickly responded to the site to aid in the breakdown and removal of the fallen material and to begin construction of a slope stabilization system. The rocks that had covered the roadway were too massive to remove whole. The crews drilled into the rocks and injected an expansive, non-explosive demolition agent to break the large rocks into manageable pieces that could be removed with traditional excavation equipment; without introducing blasts or vibrations that could destabilize the upper rock slope. Once the failed material was removed from the roadway, the rock stabilization process could begin.
The crews then drilled shear dowels into the stable material to support a reinforced shotcrete beam. The beam spanned the entire failure surface and worked with the installed dowels to support the unstable rock material above. Once the unstable rock material was
supported, GeoStabilization’s crews applied a concrete stain to the shotcrete to provide a natural look that would blend in with the surroundings.
Slip Repair with a Shoulder-Widening Retaining Wall – Calpine Corporation, Northern California