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Pre-excavation Grouting Using Multiple Grouting Techniques for CSO Project in Dearborn, MI
The City of Dearborn, Michigan, is constructing large diameter shafts to collect and treat large combined overflows during storm events to meet the federal water quality standards outlined in the Federal Clean Water Act of 1972. These shafts are strategically positioned adjacent to outfalls along the Rouge River and constructed utilizing traditional concrete shaft sinking techniques to bedrock. Geotechnical investigations for two of the 36 m (119 ft) diameter x 46 m (150 ft) deep shafts (Contract 7 and Contract 8) revealed a highly permeable soil layer designated as the contact zone and fractured rock directly above the underlying competent, but fissured bedrock. This paper focuses on one of the two projects, Contract 8, due to its challenging ground conditions. Below the contact zone, layers of pervious limestone capable of producing an inflow of tens of thousands of liters per minute presented a significant challenge for shaft sinking. Methane and hydrogen sulfide gas were also present in this fractured zone. A grouting program was implemented to construct a circular grout curtain within the contact zone and underlying bedrock to minimize water and gas infiltration during future shaft construction. Cement based suspension grout and acrylamide based solution grout were utilized to permeate the contact zone and the bedrock for creation of the grout curtain. The grout curtain was composed of a double row of holes installed around the perimeter of the future shafts. The depth of the curtain was 15 m (50 ft) below the bottom of the proposed shaft and installed in two separate phases. In the first phase the contact zone was grouted with multiple passes of both cement based and acrylamide based grouts through multiple port sleeve pipes installed to the top of bedrock. The second phase, grouting of the underlying bedrock, utilized the multiple port sleeve pipes as overburden casings. The outside row of grout holes were drilled and grouted first, allowed the filling of larger features amenable to cement based suspension grout. Subsequently, the inside row was drilled and grouted predominantly using acrylamide grout. Each hole was injected in one stage and one pass. The contact zone hydraulic conductivity before grouting typically ranged from 20 to 30 Lugeon, and the bedrock zone ranged up to 11 Lugeon. The intial Lugeon value for each grout hole was measured using initial injection pressure and flow rate of solution grout and/or water. After grouting was completed, a pump test indicated that the overall residual hydraulic conductivity of both formations was 0.2 Lugeon. The treatment shaft was successfully constructed the following year using sinking caisson techniques and bedrock excavation. Minor water inflow was observed during construction, which was easily handled, and methane and hydrogen sulfide measurements were well below the required OSHA levels.
Pre-excavation Grouting Using Multiple Grouting Techniques for CSO Project in Dearborn, MI
The City of Dearborn, Michigan, is constructing large diameter shafts to collect and treat large combined overflows during storm events to meet the federal water quality standards outlined in the Federal Clean Water Act of 1972. These shafts are strategically positioned adjacent to outfalls along the Rouge River and constructed utilizing traditional concrete shaft sinking techniques to bedrock. Geotechnical investigations for two of the 36 m (119 ft) diameter x 46 m (150 ft) deep shafts (Contract 7 and Contract 8) revealed a highly permeable soil layer designated as the contact zone and fractured rock directly above the underlying competent, but fissured bedrock. This paper focuses on one of the two projects, Contract 8, due to its challenging ground conditions. Below the contact zone, layers of pervious limestone capable of producing an inflow of tens of thousands of liters per minute presented a significant challenge for shaft sinking. Methane and hydrogen sulfide gas were also present in this fractured zone. A grouting program was implemented to construct a circular grout curtain within the contact zone and underlying bedrock to minimize water and gas infiltration during future shaft construction. Cement based suspension grout and acrylamide based solution grout were utilized to permeate the contact zone and the bedrock for creation of the grout curtain. The grout curtain was composed of a double row of holes installed around the perimeter of the future shafts. The depth of the curtain was 15 m (50 ft) below the bottom of the proposed shaft and installed in two separate phases. In the first phase the contact zone was grouted with multiple passes of both cement based and acrylamide based grouts through multiple port sleeve pipes installed to the top of bedrock. The second phase, grouting of the underlying bedrock, utilized the multiple port sleeve pipes as overburden casings. The outside row of grout holes were drilled and grouted first, allowed the filling of larger features amenable to cement based suspension grout. Subsequently, the inside row was drilled and grouted predominantly using acrylamide grout. Each hole was injected in one stage and one pass. The contact zone hydraulic conductivity before grouting typically ranged from 20 to 30 Lugeon, and the bedrock zone ranged up to 11 Lugeon. The intial Lugeon value for each grout hole was measured using initial injection pressure and flow rate of solution grout and/or water. After grouting was completed, a pump test indicated that the overall residual hydraulic conductivity of both formations was 0.2 Lugeon. The treatment shaft was successfully constructed the following year using sinking caisson techniques and bedrock excavation. Minor water inflow was observed during construction, which was easily handled, and methane and hydrogen sulfide measurements were well below the required OSHA levels.
Pre-excavation Grouting Using Multiple Grouting Techniques for CSO Project in Dearborn, MI
Myers, Timothy J. (author) / Donoghue, Holly J. (author) / Naudts, Alex (author) / Magill, David (author)
Proceedings of the Fourth International Conference on Grouting and Deep Mixing ; 2012 ; New Orleans, Louisiana, United States
Grouting and Deep Mixing 2012 ; 1431-1440
2012-08-17
Conference paper
Electronic Resource
English
Grouting , Highways and roads , Chemical grouting , Anchors , Cement , Michigan , Excavation , Cutoffs , Piles , Mixing , Shafts , Foundations , Hydraulic structures
Pre-Excavation Grouting Using Multiple Grouting Techniques for CSO Project in Dearborn, MI
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