Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 5 INTERPRETATION OF SOIL PROPERTIES
Fig. 5.22 Field K o - OCR Relationships for (a) Natural Clays and (b) Natural Sand
In general, the value of K o has an upper bound value limited by the passive coefficient, K p . The
simple Rankine value is given by:
K p = tan 2 (45° + ½ ’) = (1 + sin ’)/(1 + sin ’) (5.19)
When the in-situ K o reaches the passive value K p , fissures and cracks can develop within the soil
mass. This can be important in sloped masses since extensive fissuring is often associated with
drained strengths that are at or near the residual strength parameters (φ r ' and c r ' = 0).
5.5 FLOW PROPERTIES
Soils exhibit flow properties that control hydraulic conductivity (k), rates of consolidation,
construction behaviour, and drainage characteristics in the ground. Field measurements for soil
permeability have been discussed previously and include pumping tests with measured drawdown,
slug tests, and packer methods. Laboratory methods are presented in Section 4.6.5 and include
falling head and constant head types in permeameters. An indirect assessment of permeability can
be made from consolidation test data. Typical permeability values for a range of different soil types
are provided in Table 5.1. Results of pressure dissipation readings from piezocone and flat
dilatometer and holding tests during pressuremeter testing can be used to determine permeability
and the coefficient of consolidation (Jamiolkowski, et al. 1985).
March 2009 5-21