Permeability and its influence - Geotechnical Investigation and Design Tables - page 98

Pore water pressure u 2 measured at shoulder of 10 cm 2 piezocones.

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Multiply by 1.5 for 15 cm 2 piezocones.

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Soil mixtures would have intermediates times.

Figure 8.2 Drainage paths.

8.16 Time factors for consolidation
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T v d 2 /c v . The time to achieve a given degree of consolidation = t =

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Time Factor = T v .

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D = maximum length of the drainage path = ½ layer thickness for drainage top

and bottom.

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Degree of Consolidation = U = Consolidation settlement at a given time (t)/Final

consolidation settlement.

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α = u 0 (top)/u 0 (bottom), where u 0 = initial excess pore pressure.

Table 8.16 Time factor values (from NAVFAC DM 7-1, 1982).

Degree of Time factor T v

consolidation

1.0 0 α = α = α =∞

(two way drainage) (one way drainage - (one way drainage -

bottom only) top only)

10% 0.008 0.047 0.003

20% 0.031 0.100 0.009

30% 0.071 0.158 0.024

40% 0.126 0.221 0.048

50% 0.197 0.294 0.092

60% 0.287 0.383 0.160

70% 0.403 0.500 0.271

80% 0.567 0.665 0.440

90% 0.848 0.940 0.720