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Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

Technical Manual: Conduits through Embankment Dams (FEMA 484)

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Appendix B—Case HistoriesFigure B-66.—View of the interior of the outlet works after grouting.Settlement and crack surveys were taken, in the upstream and downstream conduits,in January of 1986 and October of 1986. The maximum settlement recorded inJanuary of 1986 was about 0.74 feet at station 11+24 in the downstream conduit.For reference, the station at the centerline of the gate chamber is located justdownstream of the centerline of the embankment dam, station 7+50. In October of1986, an additional settlement of about 0.22 feet was recorded at station 11+24.Settlements of other points in the conduit varied, seemingly based on the stiffness ofthe foundation. Maximum transverse cracking occurred in the upstream conduit atstation 7+80 and station 8+80. The downstream conduit had very little transversecracking, but a maximum joint opening of about ½ inch occurred at station 10+73.Longitudinal cracking occurred in the crown and invert between stations 6+50 and7+65 and between stations 11+74 and 14+35 in the upstream and downstreamconduits, respectively. The settlement and cracking occurred during or afterconstructing the dam embankment to elevation 6830 in the 1985 construction seasonand topping out of the dam in 1986 at elevation 6886.The settlement and cracking of concrete in the upstream conduit was addressed byrequired injecting grout in and around the cracks to reduce water leakage andpotential backward erosion piping or internal erosion of surrounding soils in theembankment dam, along with protecting the conduit reinforcement from corrosion.Polyurethane resin was used to grout the transverse cracks. Also, the polyurethaneresin grout was considered (due to its more flexible characteristics over more rigidepoxy material) for grouting the longitudinal cracks. However, longitudinal crackswere grouted with epoxy material to provide a degree of structural stability.Approximately 500 feet of cracks were designated for grouting. The contractorB-85

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