150_5320_6d_part2 - AC 150/5320-6D 7l7195 C Muskeg Muskeg...

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AC 150/5320-6D 7l7195 C. Muskeg. Muskeg is sometimes encountered in arctic areas. Muskeg is a highly organic soil deposit which is essentially a swamp. Every effort should be made to avoid pavement construction on this material. If construction in areas of muskeg is unavoidable and the soil survey shows the thickness of muskeg is less than 5 feet (1.5 m), the muskeg should be removed and replaced with granular fill. If the thickness of muskeg is too great to warrant removal and replacement, a 5 foot (1.5 m) granular fill should be placed over the muskeg. These thicknesses are based on experience and it should be anticipated that differential settlement will occur and considerable maintenance will be required to maintain a smooth surface. Use of a geotextile between the muskeg surface and the bottom of granular fill is recommended to prevent migration of the muskeg up into the granular till. In this application, the geotextile is considered to perform the function of separation. Additional information on the design and construction of geotextiles performing the separation function within pavement sections is provided in FHWA-HI-90-001 (see Appendix 4). d. Permafrost Design. Design of pavements in areas of permafrost is discussed in Chapter 3. Further information on permafrost can be found in Research Report No. FAAfRDi74130, see Appendix 4. 22
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7m95 AC150/5320-6D CHAPTER 3. PAVEMENT DESIGN SECTION 1. DESIGN CONSIDERATIONS 300. SCOPE. This chapter covers pavement design for airports serving aircraft with gross weights of 30,000 pounds (13 000 kg) or more. Chapter 5 is devoted to the design of pavements serving lighter aircraft with gross weights under 30,000 pounds (13 000 kg). 301. DESIGN PHILOSOPHY. The FAA policy of treating the design of aircraft landing gear and the design and evaluation of airport pavements as three separate entities is described in the Foreword to this advisory circular. The design of airport pavements is a complex engineering problem which involves a large number of interacting variables. The design curves presented in this chapter are based on the CBR method of design for flexible pavements and a jointed edge stress analysis for rigid pavements. Other design procedures such as those based on layered elastic analysis and those developed by The Asphalt Institute and the Portland Cement Association may be utilized to determine pavement thicknesses when approved by the FAA. These procedures will yield slightly different design thicknesses due to different basic assumptions. All pavement designs should be summarized on FAA Form 5100-1, Airport Pavement Design, which is considered to be part of the Engineer’s Report. An Engineer’s Report should be prepared for FAA review and approval along with initial plans and specifications. Because of thickness variations, the evaluation of existing pavements should be performed using the same method as was employed in the design. Procedures to be used in evaluating pavements are described in detail in Chapter 6 of this advisory circular. Details on the development of the
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This note was uploaded on 01/07/2012 for the course CEE 4674 taught by Professor Staff during the Fall '11 term at Virginia Tech.

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150_5320_6d_part2 - AC 150/5320-6D 7l7195 C Muskeg Muskeg...

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