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Dam Reinforcement


Keyser, WV: Pressure Grouting New Creek Site 14

dam-reinforcement-new-creek-wv

The project was performed for the USDA-NRCS under the American Resource Recovery and Reinvestment Act (ARRA) as part of a large-scale dam and spillway rehabilitation. The Kittlelick fault, a prominent thrust-fault feature, ran through the left abutment of the dam and was suspected to be transmitting significant amounts water through the dam foundation.

Three (3) Exploratory borings were initially installed using Rock Coring methods to assess the depth and angle of the fault.

Two lines of borings were then installed vertically through the fault and grouted (A-Line and B-Line). A third line (C-Line) was then installed perpendicular to the first two, this line was intended to be drilled and grouted within the fault alignment. Line A and B Grout borings were installed vertically. C-Line borings were installed at the fault angle of 58-degrees.

Grouting of the bedrock progressed in approximately 20-foot ascending stages intended to isolate the fault to the extent practical and also address any overlying weathered bedrock. Grout passed through Geo-Con's "Accugrout" header system containing high-precision pressure and flow control valves, mag-flow meter and electronic pressure transducer, with on-board displays prior to delivery to the grout stage. Geo-Con established a grouting program that included progressive grout viscosity adjustment and flow rate limitations in response to real-time assessment of grouting parameters.

The goal of the program was to address the fault location where it crossed the spillway. This was accomplished by achieving efficient refusal/closure of fractures while maintaining a limited grouting reach in each boring. Stages were isolated with a grout packer apparatus that consisted of a single pneumatic packer attached to the bottom of an aluminum grout pipe. Grout flow rates, apparent lugeon, pressure, and total gallons of grout pumped were recorded and used to generate grouting reports for each stage.

Geo-Con developed 2 grouts for the project as specified (50 second viscosity and 85 second viscosity). At the onset of the project it became apparent that the fault was actually comprised of a network of small fractures, rather than a large open fracture, and a thinner grout mix was needed (35 second viscosity) to address this condition. Because of Geo-Con's expertise and innovative methods for developing project-specific grout mixes, a starter mix was easily developed on site without delay, and the engineer was able to successfully utilize three mixes for the duration of the project.

The work area was very small and recessed into the emergency spillway area. Coordination of drilling and grouting crews was a constant challenge. The project was completed ahead of schedule and without any Health and Safety incidents or accidents.



 

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