Question

CIVL 311 Soil Mechanics Lab HWE2 Problem 2.1 The grain size distribution, liquid limit, and plastic limit for several soils are shown below. • Determine the USCS group symbol and group name for soils through G. • Determine the AASHTO group classification and group index for soils through G. (The #10 sleve has an opening size of 2mm.) • Rank the four soils through G in order of best to worst highway subgrade. Which of the following USCS soils would probably receive the best rating for use as a highway subgrade per the AASHTO classification: CL, SM, ML, or SW? Why? FINES SAND Medium GRAVEL Fine Course I MO Fine Coarsel 1024 Percent finer by weight 0.01 0002 0.4 0.1 0.19 0. 3 1 - Particle size (mm) Soil Sample Identification Liquid Limit Plastic Limit 6033 40 30 30 26 Non-plastic Page 1 of 1

Answer 1

(a) As per USCS

Soil D percent finer than #200 seive = 82% 7127. 50% So it is clay or silt. L = 60% 750% (highly plastic) P1 = LL-PL = 60-33 = 27 77 ie clay. Soils is CH or flighty plastic day Soil E % finer than 200 seine = 72% 50% so it is clay or silt. LLE 40 < 50 but 35% (Intermediate PI = 11-P2 = 40-30=1077 ie clay Soil & is Intermediate plastic clay or CI plastic) so it have Soil F: 7. fines than 200 Siene = 36% < 50% So it is Gravel or sand. more than 12% passes through 757 sieve clay or sitt. #4 retained % is o so it is sand. : PI = LL-PI = 30-26 = 4 ie sitt so it is silly and or ss

< 50% = 7% < 50% Soil G Hon plastic % finer than #200 seive = 6% so it sand or Grand # 4 retained t = 100 - 93% so it is sand. DO = 2 mm D30 = 0.30mm D10 = 0.1 mm Cu- Doo 2 = 20 6 Cc D - (0.3)= 0.45 DooD10 0.182 So it is well graded sand ie hา Dio O SW.
(b) As per AASHTO

(c) & (d)

soil D ) finer than # 200 seive = 821 7 36%. So silt-clay Material (A4 to A7) LL=60 PL = 33 it in A7 it is clayey soil. Soil & % finer than So silt - clay U= 40 PL=30 200 seive = 72% 7 36% Material (Ay to Az). it in A (clayey soil) Soil Fi % finer than #200 seive = 36% 7,36%. So silt - clay Material. 1 - 30 it is Ay (silty swil-) PL = 26 Soil Gi 7. finer than # 200 seive = 6% < 35%. so it is Granular material. #10 /. passing = 72% it is A3 (fine sand

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A Ranking of soil from worst to best to worst. Soil G« Soilf, soilk, soil D (as per AASHTO) # SW, SM, ML, CL is the ranking from best to worst for use as a highway subgrade,