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Classify soil, No. 4 70%, No. 200 30%

Short answer

SC, clayey sand with gravel. Fines 30% (>12%) are classified by plasticity; sand dominates coarse fraction (40% sand vs 30% gravel). Ip=22 lies above A-line value 9.5, so fines are clayey.

Classify the following soil if the test results obtained from sieve analysis and consistency tests are given below: Percentage passing No. 4 sieve (4.75 mm) = 70%, percentage passing No. 200 sieve (0.075 mm) = 30%; liquid limit = 33% and plastic limit = 11%.

Given

Passing No. 4 =70%= 70\%; passing No. 200 =30%= 30\%; wL=33%w_L = 33\%; wP=11%w_P = 11\%.

Ip=wL−wP=33−11=22%I_p = w_L - w_P = 33 - 11 = 22\%

Step 1: Coarse or fine?

70% is retained on the No. 200 sieve, so the soil is coarse-grained.

Step 2: Gravel or sand?

  • Gravel (retained on No. 4) =100−70=30%= 100 - 70 = 30\%
  • Sand =70−30=40%= 70 - 30 = 40\%

Gravel is 30/70 = 43% of the coarse fraction (less than half), so the soil is sand (S).

Step 3: Fines

Fines are 30% (more than 12%), so classify the fines with the plasticity chart.

Ip,A-line=0.73(33−20)=9.5%I_{p,A\text{-line}} = 0.73(33 - 20) = 9.5\%

Ip=22I_p = 22 is above the A-line and greater than 7: clayey fines (C).

Answer: SC, clayey sand (with gravel).

✓ Answer checked by Claude Opus 5.5 (high effort)

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