Page 304 - Planning and Design of Airports
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Value as Base Directly Subgrade Unit Dry Drainage Compressi- under Modulus Weight Charac- bility and Potential Frost Wearing k (pci) CBR (pcf) teristic Expansion Action Surface (12) (11) (10) (9) (8) (7) (6) 300 or 60–80 125–140 Excellent Almost none None to very Good more slight
Value as Base Directly under Wearing Surface (5) Excellent Good Good to excellent Good Good to excellent Good Fair to good Fair to good Good Fair to good
(4) Gravel or sandy gravel, well graded Gravel or sandy gravel, poorly graded Gravel or sandy gravel, uniformly Silty gravel or silty Clayey gravel or clayey Sand or gravelly sand, Sand or gravelly sand, Sand or gravelly sand, Poor uniformly Not suitable graded Silty sand or silty
Name graded sandy gravel sandy gravel well graded poorly graded gravelly sand gravelly sand
Letter (3) GW GP GU GM GC SW SP SU SM SC
Major Divisions (2) (1) Gravel and gravelly soils Coarse- gravelly soils Sand and sandy soils
