PROJECT PROFILE Deterioration of sedimentary rocks forming a nearly vertical slope between a light-rail transit tunnel portal and a roadway 170 feet above the tunnel threatened both the tunnel portal and roadway. The exposed rock face in- cluded a massive sandstone layer ap- proximately 45 feet thick underlain by erodible clay shale strata. Intersecting vertical joint sets in the sandstone had created large sandstone columns that were

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