REHABILITATION OF LAKE SHERBURNE DAM OUTLET WORKS USINGSILICA FUME CONCRETE

摘要

Lake Sherburne Dam, located on Swift Current Creek, a tributary of the St. Mary River,near the east boundary of Glacier National Park, is a principal component of the MilkRiver Project, which furnishes water for the irrigation of approximately 110,300 acres ofland in north central Montana, approximately 90 miles northeast of Kalispel. The damwas completed in 1921. The outlet works and spillway both discharge into a doublebarreledconduit. Each barrel of the conduit is 6-feet-wide by 8-feet-high, with a crownradius of 3 feet and an invert radius of 5 feet. Active landslide activity in areas along thereservoir rim results in the entry of a significant amount of gravel, cobbles, and bouldersinto the reservoir. A portion of this debris eventually travels to the intake structure of theoutlet works and is carried by high velocity flows through the double-barreled conduitduring reservoir releases. The abrasive action of this debris on the conduit over the yearshas resulted in significant erosion of the conduit inverts and walls. A project wascompleted in 2007 and 2008 which rehabilitated the conduit by restoring the originalgeometry of the inverts and walls using silica fume concrete. The high compressivestrength of silica fume concrete is believed to provide a longer service life than aconventional concrete repair given the severe abrasive loading acting on the conduit. Therepair thickness varied between 5 to 6 inches and included one layer of #4 reinforcement.The repair was anchored to the existing concrete using epoxy concrete anchors.Contraction joints were spaced at 10 feet along the length of each conduit, andhydrophilic strip waterstop surrounded the perimeter of each repair section.