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Title: Evaluation of XM20 and XM20E1 landing mats under heavy-duty load
Authors: United States. Army Materiel Command.
Smith, Carroll J.
Keywords: Dow landing mats
Landing mat
XM20 landing mat
XM20E1 landing mat
Publisher: Soils and Pavements Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous Paper (U.S. Army Engineer Waterways Experiment Station) ; S-72-39
Description: Miscellaneous Paper
Abstract: This report describes investigations conducted to evaluate two aluminum alloy landing mats manufactured by the Dow Chemical Company, Madison, Ill. These mats were designated as XM20 and XM20E1, and they are one-piece hollow extrusions fabricated from 6061 aluminum alloy artificially aged to the T6 condition. The XM20E1 mat is basically identical in design with the XM20 mat with the exception that geometrical changes in both male and female connectors wer e incorporated in the XM20 design to provide additional strength in these areas. Both the XM20 and the XM20E1 mats are interlocked along the sides by means of hinge-type connectors, the components of which are an integral part of the basic panel extrusion. End connectors are composed of extruded connectors welded to the basic panel and consist of an overlap and underlap section secured by a locking bar after individual panels have been joined together. These investigations consisted of traffic, skid, and laboratory tests to obtain information for use in evaluating the mats for potential use as heavy-duty landing mats. An AM2 repair panel was also included in the XM20 test in order to evaluate its performance under heavy-duty load conditions. The XM20 mat was also evaluated as a medium-duty mat in a previous investigation. The test data reported herein were evaluated against the criteria for heavy- duty mat as established in the revised Qualitative Materiel Requirement (QMR). Traffic tests were conducted with the mats placed on a prepared subgrade and trafficked with a rolling wheel load simulating actual aircraft operations. The XM20 and XM20E1 mats were assembled at an average rate of 445 and 617 sq ft per man-hour, respectively. These placing rates exceeded the minimum QMR rate of 150 sq ft per man-hour. The average weights of the XM20 and XM20E1 mats were 6.09 and 6.05 lb per square-foot of placing area, respectively. The traffic tests were conducted with a 50,000-lb single-wheel load with a tire-inflation pressure of 250 psi on a mat-surfaced subgrade with initial average CBR's of 3.6 and 4.0 for the XM20 and XM20E1 mats, respectively. Results indicated that when placed on a subgrade with a rated CBR of 4.0, the XM20 mat would sustain 610 coverages of traffic, and the XM20E1 mat would sustain 620 coverages. These results did not meet the QMR service life of 1000 coverages on a 4.0-CBR subgrade for a heavy-duty mat. The AM2 repair panel sustained 124 coverages on a subgrade with a CBR of 3.6. The average coefficients of friction obtained from wet and dry skid tests were 0.38 and 0.52, respectively, for the XM20 mat and 0.34 and 0.56, respectively, for the XM20E1 mat. The coefficients of friction on wet surfaces for both mats fell below the QMR coefficient of friction range of 0.4 to 0.8. The coefficient s of frict ion of 0.38 and 0.52 for the XM20 mat were determined in a previous investigation wherein it was evaluated as a medium-duty mat. Laboratory tests conducted on both mats indicated that the 6061-T6 alloy exceeded the minimum physical requirements stipulated.
Gov't Doc #: Miscellaneous Paper S-72-39
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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