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|Title:||Landing mat overlay on deteriorated pavement : bare base support|
|Authors:||United States. Air Force.|
Burns, Cecil D.
Brabston, W. N. (William Newell)
|Keywords:||Bare base support|
|Publisher:||U.S. Army Engineer Waterways Experiment Station.|
Engineer Research and Development Center (U.S.)
|Series/Report no.:||Miscellaneous Paper (U.S. Army Engineer Waterways Experiment Station) ; S-69-27|
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.
|Gov't Doc #:||Miscellaneous Paper S-69-27|
|Appears in Collections:||Documents|