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<br />Flow <br /> <br />II st Row of Blocks in Trench <br />Duckbill Anchors @ 4 ft. <br /> <br />t <br /> <br /> -, <br /> f' <br /> Xl <br /> 1,1 <br />ling <br />- ')t _'((8(2 <br /> I' <br />, <br /> X2 <br />I , <br />~- <br />~- Plan <br />~- <br /> <br />I- <br />I <br />I I I i <br />, I I ' <br />LJ~ <br /> <br />12' <br /> <br />IS' <br /> <br />Grou <br /> <br />15' <br /> <br />TOP VIEW <br /> <br />/ <br />j <br />I <br /> <br />\ =1hB <br /> <br />SECTION <br />Figure 4.6 Suggested cable-tied mat dimensions for scour protection around <br />circular bridge piers (McCorquodale). <br /> <br />Guidelines for Seal around Pier <br /> <br />An observed key point of failure for articulated block systems at bridge piers occurs at the <br />seal where the mat meets the bridge pier. During the flume studies at the University of <br />Windsor, the mat was grouted to the pier to prevent scouring of the sediments adjacent to <br />the pier. This procedure worked successfully in the laboratory, but there are implications <br />which must be considered when using this technique in the field. The transfer of moments <br />from the mat to the pier may affect the structural stability of the pier. When the mat is <br />attached to the pier the increased loadings on the pier must be investigated. <br /> <br />The State of Minnesota Department of Transportation (MnDOT) has installed a cable-tied <br />mat for a pier at TH 32 over Clearwater River at Red Lake Falls. MnDOT recommends the <br />use of tension anchors in addition to grout around the pier seal. Anchors can provide <br />additional support for the mat and grout at the pier seal will reduce scouring underneath the <br />mal. MnDOT provided the following specifications: <br /> <br />Anchors: <br />Use Duckbill anchors, 0.9 - 1.2 m (3 - 4 ft) deep. Use Duckbill anchors at corners and about <br />every 2.4 m (8 ft) around pier footings. <br /> <br />4.14 <br />