Repair of Failing MSE Railroad Bridge Abutment

In 1978, Idaho Transportation Department (ITD) designed and constructed the first U.S. "true" MSE bridge abutment over the Union Pacific Railroad (UPRR) tracks in Soda Springs. This project was one of the six original FHWA Demonstration Projects introducing reinforced earth technology to the U.S. transportation industry. In the summer of 2002, approximately six of the precast concrete facing panels "popped out" in a localized area of one of the MSE earth retaining walls supporting the bridge approaches. It was determined that the galvanized steel soil reinforcing strips had corroded at the panel connection to a point where the lateral earth pressures exceeded the connection's remaining capacity. Concerned, ITD and UPRR officials immediately prepared the contract documents for the repair of approximately 3,700 m² of MSE walls and bridge abutments. The scope of work in the ITD contract documents included installing horizontal drilled and grouted crosstie ground anchors in the approach walls, anchored soldier piles at the abutments and a reinforced shotcrete facing structurally attached to the existing MSE facing panels. The crosstie anchors connected the "back-to-back" MSE approach walls located approximately 25 m from panel to panel. Challenges included traffic control and rail traffic sequencing, winter construction, monitoring the condition of the existing structures, drilling ground anchors (from panel to panel) horizontally through a compacted fill with thousands of steel soil reinforcing elements and installing the soldier pile and rock anchor elements from the existing bridge deck.