How do we find the oercent of gravel, sand, fines for soil soil A, C, F? 1. You

Question

How do we find the oercent of gravel, sand, fines for soil soil A, C, F? 1. You have collected soil samples as part of the investigation for a highway project. The grain-size distribution data for the four soil samples are shown in the figure below as soils A through F. Soil C has a strong organic smell but contains no fibrous material. The other soils are nonorganic. From your Atterberg limit tests on the -40 portion of theses samples, you have measured the following data in Table 1. Determine the USCS group symbol and group name for soils A, C, and F using the data given below and complete the unknowns in Table 2 on the next page. Which of those soils would be the best highway subgrade for AASHTO purposes? (Note: You don't need to determine AASHTO for this) (35 points) Table 1: Soil index property results USCs Soll F 72 60 28 Soll B Soll D Soll E Soll C 14 Soll A 14 Soil wn (96) 113 35 35 27 29 PL PI LI 18 17 3.8 -2.5 Figurel: Particle grain size analysis Particle Size Distribution GRAVEL SAND SILT or CLAY Fine Fe Couse Medinum 80 70 70 50 50 20 YDpCA) 0.1 0.01 0.001 Grain size in millimeters Soll C Soll D Soll E Soll F

Explanation / Answer

Simply look for the percent of the soil mass

coarser than 4.75 mm --> Gravel

b/w 4.75 mm and 0.074 mm --> Sand

finer than 0.074 mm ---- Fine grained soil.

For example,

for soil A - % passing 4.75 mm is 27%, than means 63% is retained, so % of gravel is 63%.

about 3% passes 0.074mm, so soil in the sand range = 27-3 = 24%.

and %age of fines = 3%

Simply read the graph.

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