REMEDIATION OF RCC DAM SEEPAGE UPPER STILLWATER DAM REHABILITATION – PHASE I

摘要

Since the time of initial construction a series of cracks have developed through the Upper Stillwater Dam structure extending from the upstream face to the downstream face and vertically from the crest to the underlying bedrock foundation. A remediation program was implemented consisting of chemical grouting and for certain locations installing a membrane liner across the crack plane extending from the top of the dam into the underlying bedrock. The Upper Stillwater Dam Rehabilitation Project is unique primarily in the manner employed to construct the membrane slots, each 14-ft. long with a minimum opening width of 4.5 inches to depths of 158-ft, 182-ft, and 240-ft. respectively, as well as the design and implementation of the stainless steel membrane systems. Construction of a typical slot consisted of drilling a series of overlapping drill holes using a percussion drilling system modified with a unique guide system. An initial pilot hole was core drilled to the depth of the slot followed with a percussion drilling system fitted with a special guide sleeve designed to follow the profile of each sequential slot hole to ensure a high degree of verticality and bearing alignment with adjacent slot holes. The corrugated stainless steel membrane was designed for expansion based on the total movement of the crack throughout the seasonal temperature cycles. Finally, the upstream and downstream annular spaces of the slot-membrane are back-filled with a special hot asphalt/portland cement mixture specifically designed for adhesion to stainless steel and concrete, resilience, and expansion properties.