Geology Reference
In-Depth Information
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Putting numbers to geology
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Hoek (1999)
For civil engineering design, it is necessary to assign physical properties
to each unit of soil or rock within a ground model. These include
readily measurable or estimated attributes such as unit weight, density
and porosity. Other parameters that are often needed are strength,
deformability and permeability. In the case of aggregates (rock used in
construction for making concrete) and for armourstone, important
attributes are durability and chemical stability.
field or the laboratory and need to be scaled up according to theoretical
or empirical rules, to include for geological variability, fabric and
structure. For example, a soil mass might be made up of a mixture of
strong boulders in a matrix of weak, soil-like material, and this mix has
to be accounted for in assigning parameters for engineering design.
Mass strength, deformability and permeability of rock masses are
controlled largely by the fracture network, rather than intact rock
properties; the permeability of intact rock might be 10
−
11
m/sec,
which could be thousands of times lower than for the fractured
rock mass.
5.3.1 Fundamentals
The strength of soil and rock (geomaterials) is derived from friction
between individual grains, from cohesion derived from cementation
