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Pipe lift hole plugs resist internal pressure and backfill surcharge loads.

Popit Inc. designed its signature lift hole plug to be used in storm pipe, with a constant flow of water offering no internal pressure. The company recently enlisted researchers to determine if, in fact, the plastic plug can withstand internal pressure--coupled with backfill--without affecting seal integrity.

There are currently no standard specifications for testing products such as Popit installed in concrete pipes when subjected to internal pressure and backfill height. Dr. All Abolmaali and Dr. Y. Park from the University of Texas Center for Structural Engineering and Research Simulation developed a procedure and conducted a testing program to evaluate the pressure resistance characteristics of Popit plugs installed in mechanical (smooth) and handmade (rough) lift holes.

Against the backdrop of Hanson Pipe & Products' Grand Prairie, Texas, flagship plant, 10 24-in.-diameter concrete pipes with rough lift holes were randomly selected to offer a range of void dimensions. Introduction of lift holes in 24-in. pipes would represent one of the most critical conditions when compared with larger-diameter products. To ensure water tightness, concrete bulkheads were installed at each pipe end similar to those used in the hydrostatic test (ASTM C497). One joint of a gasket pipe was tested with bulkhead installed on each side for water tightness without backfill.

The rough lift hole dimensions were measured in randomly selected Hanson stock pipe to compare their range of the lift hole sizes with that of the testing samples, confirming that study results are widely applicable to most concrete pipe. The range of variation for rough lift hole dimensions of pipe diameters larger than 24 in. should be similar or smaller than those presented due to their higher bending action, researchers note, pointing likewise to smaller diameter products' hoop action.

For the rough lift holes with a high degree of irregularities, the Popit plugs are able to hold internal pressures in the range of 7 to 11 psi. For smooth mechanical holes, they resist internal pressure as high as 18 psi. Dr. Abolmaali and Dr. Park observed sample plug characteristics and performance in the presence of an experienced pressure operator, who logged psi data with Vishay scanner and transducer. After removal of internal pressure and backfill loads, no damage, tear, fracture, bending or compromise of structural integrity was recorded in rough or smooth hole plugs. Researchers concluded that the Popit product has high resistance to internal pressure and surcharge loads of up to 30 ft. of backfill height.

The full "Internal Pressure and Backfill Load Resistance Characteristics of 'Popit' Lift Hole Plugs" report can be obtained from the What's New section at the American Concrete Pipe Association home page, Inc., 215/752-8410;;

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Publication:Concrete Products
Date:Jan 1, 2013
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