Knowledge Core Collection:
https://hdl.handle.net/11681/46474
2024-03-28T22:01:32ZEvaluation of May two-piece AM2 landing mat
https://hdl.handle.net/11681/22683
Title: Evaluation of May two-piece AM2 landing mat
Authors: Grau, Robert W. (Robert Walter)
Abstract: This investigation was conducted to evaluate two-piece AM2 landing mat extruded and fabricated by May Aluminum, Inc., El Campo, Texas. The mat was fabricated from two 12-in. -wide extrusions welded together to form a 2-ft-wide plank. A test section consisting of one sand and two clay subgrade items with various CBR strength values was constructed and surfaced with the mat. The test section was subjected to uniform coverage and single-line traffic representing operations of an aircraft having a 60,000-lb gross weight with a single-wheel main-gear assembly load of 27,000 lb with a 30-7.7 tire inflated to 100 psi. Based on the results obtained in this study, it is concluded that: A. The May two-piece AM2 will sustain 1600 cycles (188 coverages) of aircraft operations with a 27,000 lb single-wheel load and 400-psi tire-inflation pressure when placed on a subgrade having a CBR of 4.1 or greater throughout the period of traffic. B. The May two-piece AM2 will sustain 1600 passes of a 27,000-lb single-wheel load with a tire-inflation pressure of 400 psi in a single path located 1-1/2 ft or more from the mat end joints when placed on a sub grade having a CBR of 4.3 or greater throughout the period of traffic. C. General behavior of the mat in these tests was not materially affected by the two-piece nature of the planks.
Description: Miscellaneous Paper1968-07-01T00:00:00ZEvaluation of Dow Chemical extruded truss-web landing mat
https://hdl.handle.net/11681/21000
Title: Evaluation of Dow Chemical extruded truss-web landing mat
Authors: White, D. W. (Dewey W.)
Description: Miscellaneous Paper; Abstract: The inves tigation reported herein was conducted to evaluate 2- by 24-ft truss-web aluminum alloy extrusions without end connectors and truss-web aluminum alloy heavy-duty landing mat designed by Dow Chemical Company, Midland, Mich. The truss-web extrusions were one-piece multi-hollow 6061-T6 aluminum alloy extrusions without end connectors and were 1-1/2 in. thick, 2 ft wide, and 24 ft long. No antiskid material was applied to the extrusions. After the 2- by 24-ft truss-web extrusions were tested under traffic , Dow supplied 2- by 9- ft landing-mat panels, and these were evaluated. The mat is a one-piece multi-hollow extrusion fabricated from 6061-T6 aluminum alloy, 1-1/2 in. thick, 2 ft wide, and 9 ft long, and has antiskid material on the top surface. The investigation of the mat consisted of traffic tests; skid tests; cable roll-over, hook- impact, jet-blast, and temperature-impingement tests; and laboratory tests. The tests were designed to evaluate the service life and performance of the truss-web mat in accordance with the Qualitative Materiel Requirement. Traffic tests were conducted on quantities of the 2- by 24-ft extrusions (internal ribs and side connectors perpendicular to the direction of wheel travel of load cart) without end connectors; 2- by 9-ft truss-web mat placed in the standard placement pattern (side connectors and internal ribs perpendicular to the direction of wheel travel); and 2- by 9-ft mat placed in a longitudinal placement pattern (side connectors and internal ribs parallel to wheel travel). The traffic tests were conducted with the 24-ft-long extrusions and 9-ft-long mats on prepared subgrades using rolling-wheel loads simulating actual aircraft eperations. The truss-web extrusions withstood 1534 coverages (1410 coverages on a subgrade with a 4.0 CBR) and an additional 2466 single-line passes on a 5.0 CBR (total of 4000 passes on one lane of the test section). A total of 2000 coverages (equivalent to 1612 coverages on subgrade with a 4.0 CBR) were applied on the 2- by 9-ft mat in the standard placement pattern before failure occurred. Two hundred coverages (equivalent to 240 coverages on a subgrade with a 4.0 CBR) were applied on the truss-web mat in the longitudinal pattern before the hinging action of the mat allowed the subgrade to flow outward from the center of the test section. This caused a trough to form; thus, the test section was considered failed due to roughness. Laboratory tensile-strength tests conducted on samples taken from the top sheet, ribs, and bottom sheet of truss-web landing mat revealed that the tensile strength of the material was within specified requirements. Further study and testing are recommended in order to develep a waterproof version of truss-web landing mat, which will eliminate the requirement for membrane to be placed beneath the mat to prevent water penetration into the subgrade. This water penetration causes the subgrade strength to deteriorate. Service tests of the truss-web landing mat are recommended to validate the findings of the engineer tests. The standard placement pattern is recommended for use in the service tests.
NOTE: This file is large. Allow your browser several minutes to download the file.1972-12-01T00:00:00ZEvaluation of XM20 and XM20E1 landing mats under heavy-duty load
https://hdl.handle.net/11681/20999
Title: Evaluation of XM20 and XM20E1 landing mats under heavy-duty load
Authors: Smith, Carroll J.
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.1972-12-01T00:00:00ZLanding mat overlay on deteriorated pavement : bare base support
https://hdl.handle.net/11681/20997
Title: Landing mat overlay on deteriorated pavement : bare base support
Authors: Burns, Cecil D.; Brabston, W. N. (William Newell)
Description: Miscellaneous Paper; Abstract: The objective of this study was to develop procedures for overlaying rough, deteriorated pavements, such as old, abandoned airfields or highways, with new landing mat in order to provide an adequately smooth runway or taxiway for the operation of tactical aircraft. The objective was accomplished by constructing an overlay test section consisting of six test items on a rough, deteriorated asphaltic concrete surface and applying test traffic with a 25,000-lb single-wheel load on a 30x11.5, 24-PR tire inflated to 250 psi.
The test section was initially constructed as follows:
Item 1 : a thin leveling course of sand surfaced with XM18 mat.
Item 2 : a thin leveling course of sand surfaced with XM19 mat.
Item 3 : a thin leveling course of clay gravel surfaced with
XM19 mat.
Item 4 : a 4-in.-thick (minimum) cushion of clay gravel surfaced with XM19 mat.
Item 5 : a 4-in.-thick (minimum) cushion of compacted lean clay protected with T16 membrane and surfaced with XM19 mat.
Item 6 : Item 6 - a 4-in.-thick (minimum) cushion of compacted lean clay protected with WX18 membrane (not surfaced with landing mat).
A total of 2170 coverages of test traffic was applied to items 1-5 and 510 coverages to item 6. Test traffic was applied in both dry and wet weather. During the test period, several modifications were made in items 1-4 in order to prevent soil pumping under traffic in wet weather. In items 1 and 2, T16 membrane was placed between the sand leveling course and the landing mat. A piece of WX18 membrane was placed on half of the clay gravel leveling course under the XM19 in item 3. The clay gravel in the remainder of item 3 and all of item 4 was stabilized with 6 percent portland cement by soil weight.
From the results of this test, it was concluded that:
(A.) Rough, deteriorated pavements can be overlaid with a soil cushioning layer and new landing mat to provide an adequate surface for the operation of tactical aircraft.
(B.) Both fine-grained and granular soils can be used as the leveling or cushioning layer. However, both types of material will require protection to prevent pumping of the fines through mat joints during wet-weather traffic operations.
(C.) T16 membrane placed between soil and mat is quite effective in protecting fine-grained cohesive soil or fine sand from moisture infiltration and pumping action during wet weather. However, when used between soil and mat, neither the T16 nor the heavier WX18 membrane is adequate to withstand the abrasive action of sharp objects in the soil, such as the coarse aggregate in the clay gravel material. For this reason, care must be taken to remove roots, rocks, and other sharp objects from soils used under waterproof membrane in overlay construction.
(D.) A clay gravel cushion can be effectively protected from water infiltration by stabilization with 6 percent portland cement by soil weight.
(E.) The optimum thickness of leveling or cushioning material needed for mat overlay construction is the minimum thickness that will: (1.) provide uniform bearing for the mat, (2.) provide an adequate transverse slope or crown (approximately 2-1/2 to 3 percent), and (3.) allow a sufficient quantity of soil so that the material can be easily placed and compacted with the available construction equipment.1969-06-01T00:00:00Z