Soil nailing to be utilized to repair I-90 Marshall Hill slides

Sheridan, Wyo – Motorists traveling on I-90 east of Sheridan will notice a lane closure of the westbound lane near mile marker 30. 

The mid-October snow storm, which dropped over ten inches of heavy wet snow, was just a bit too much for a 300 foot section of the right hand travel lane, thus resulting in the loss of roughly 175 feet of shoulder and guardrail.

A common occurrence in Sheridan County, a slope failure happens when the soils, commonly clay, become overly saturated and lose their ‘sticky’ factor and give way to gravitational pull. Most of these clays are sitting on a shale base which offers little to no resistance for the clay to adhere to. The soils become too heavy and follow the path of least resistance and fall away from the slope.

In the instance, 150 feet of guardrail and pavement went along with it resulting in the closure of the driving lane until repairs are made.

The Wyoming Department of Transportation Geology team spent a week testing the soils in over a dozen locations on either side of the slide as far down as fifty feet to determine how saturated the soils are throughout the slide area. This method allows geologists to determine if there is the potential for more sliding to occur in the near future. 

Results indicate the slide has settled and geologists have determined that the best method to repair the slope is to place soil nails into the side of the slope.  

Soil nailing is a remedial construction measure to treat unstable natural soil slopes. It involves drilling holes for steel bars to be inserted into a slope face which are then grouted in place. Mesh is attached to the bar ends to hold the slope face in position.

Temporary repair work is anticipated to begin by the end of the month.  The travel lane will remain closed until repairs are completed. 
 

 Contractors securing wire mesh to an embankment of a slide repair in western Wyoming (WYDOT Photo).