Page 305 - Planning and Design of Airports

Subgrade Modulus k (pci) (12) 300 or more 300 or more 300 or more 300 or more 200–300 200–300 200–300 200–300 200–300 200–300

CBR (11) 60–80 35–60 25–50 40–80 20–40 20–40 15–25 10–20 20–40 10–20

Unit Dry Weight (pcf) (10) 125–140 120–130 115–125 130–145 120–140 110–130 105–120 100–115 120–135 105–130

Drainage Charac- teristic (9) Excellent Excellent Excellent Fair to poor Poor to practically impervious Excellent Excellent Excellent Fair to poor Poor to practically impervious

Compressi- bility and Expansion (8) Almost none Almost none Almost none Very slight Slight Almost none Almost none Almost none Very slight Slight to medium

Potential Frost Action (7) None to very slight None to very slight None to very slight Slight to medium Slight to medium None to very slight None to very slight None to very slight Slight to high Slight to high

Value as Base Directly under Wearing Surface (6) Good Poor to fair Poor Fair to good Poor Poor to not suitable Not suitable Poor Not suitable Not suitable

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