Page 299 - Planning and Design of Airports

260 Airp o r t D e sign

Area Spacing Depth
Runways and Random across Cut areas—10 ft (3.5 m)
taxiways pavement at 200 ft below finished grade
(68 m) intervals Fill areas—10 ft (3.5 m)
below existing ground
Other areas of One boring per Cut areas—10 ft (3.5 m)
pavement 10,000 ft (930 m ) below finished grade
2
2
of area Fill areas—10 ft (3.5 m)
below existing ground
Borrow areas Sufficient tests to To depth of borrow
clearly define the excavation
borrow material

Note: For deep fills, boring depths shall be sufficient to determine the extent of consolida-
tion and/or slippage the fill may cause.

TABLE 7-1 Recommended Soil Boring Spacings and Depths

Major Divisions Group Symbols
Coarse-grained soils Gravels 50% or more Clean gravels GW
more than 50% of coarse fraction GP
retained on No. 200 retained on No. 4 sieve
Gravels with fines GM
sieve
GC
Sands less than 50% Clean sands SW
of coarse fraction SP
retained on No. 4 sieve
Sands with fines SM
SC
Fine-grained Silts and clays liquid limit 50% or less ML
soils 50% or less CL
retained on No. 200
OL
sieve
Silts and clays liquid limit greater than 50% MH
CH
OH
Highly organic soils PT

Note: Based on the material passing the 3-in (75-mm) sieve.
TABLE 7-2 Classification of Soils for Airport Pavement Applications