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Table 7 Soil indices and parameters for shale soil from other studies

From: Occurrence of shale soils along the Calabar-Itu highway, Southeastern Nigeria and their implication for the subgrade construction

Parameter Nkporo shale New Netim marl Ekenkpon shale Igumalea shale Abakalikib shale Pulaski county, Kentucky, USA shale soilc
Fines (% passing sieve no 200) 80.1 68.4 81.4 90 90–92 29–46f
Plastic limit 30.0 33.0 38.4 27 17–23 18–23
Liquid limit 52.0 48.0 52.8 72 53–68 40-57
Plasticity index 22.0 15.0 14.4 45 36–45 22-34
Liquidity indexe −0.2 −1.2 −0.7 −0.04 0.14-0.11 0.02 to −0.08
Compression index Ccd 0.378 0.342 0.385 0.558 0.387–0.522 0.27–0.423
AASHTO classification A-7-5(20) A7-5(11) A-7-5(15) A-7-6 A-7-6 A-6(14) and A-7-6(25-27)
USCS classification OH MH OH CH CH CL and CH
Maximum dry density (Mg/m3) 1620.0 2020.0 1700.0 1510 1830–1890 N.L.
Optimum moisture content (%) 14.6 8.6 16.6 22 12.0–12.5 N.L.
CBR (%) (after 24 h soaking) 26.8 20.6 7.0 0.68 38–55 3
Free swell (%) N.D N.D N.D. 50 48–52 N.L.
Specific gravity N.D N.D N.D. 2.55 2.42–2.56 2.56 -2.79
Colour Black Yellowish Dark grey Grey Bluish–Brownish Red
Natural moisture content (%) 26.3 15.6 27.8 25 22-28 17.5–25.8
pH 2.27 6.97 4.28 6.83 N.L. N.L.
Unconfined compressive strength (kN/m2) 784.19 674.53 350.57 400 N.L. 100.4
  1. N.D. not determined, N.L. not listed by author
  2. * In-situ value
  3. aManasseh and Olufemi (2008)
  4. bAghamelu and Okogbue (2011)
  5. cHopkins et al. (2006)
  6. dValues from computed from Cc = 0.09 (LL − 10)
  7. eComputed
  8. f% finer than 0.002 mm (clay fraction)