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1. Sensitive, fine grained 6. Sands – clean sand to silty sand
2. Organic soils – peats 7. Gravelly sand to dense sand
3. Clays – silty clay to clay 8. Very stiff sand to clayey sand*
4. Silt Mixtures – clayey silt to silty clay 9. Very stiff, fine grained*
5. Sand Mixtures – silty sand to sandy silt
* Heavily overconsolidated or cemented
Figure 3.8: Normalized CPT Soil Behavior Type Chart (after Robertson and Wride 1997a, b)
An empirical Soil Behavior Type Index, I c , has been proposed for use in
estimating the fines content of the soil from the Q and F values. The Soil
Behavior Type Index is defined in Equation 3-10. This index parameter is used to
convert the measured CPT tip resistance to the value that would be expected for
an equivalent clean sand. Ranges of I c for the soil types illustrated in Figure 3.8
are provided in Table 3.6. Once I c has been determined, the fines content of the
soil can be estimated by an empirical relationship based on the soil zones in
Figure 3.8.
I c
2
2
3.47 logQ logF
1.22
0.5
(3-10)
61