Geology Reference
In-Depth Information
Figure 3.1 Massive
horizontally
bedded Eocene
conglomerate and
sandstone,
unconformably
overlying Triassic
Lower
Muschelkalk,
north of Falset,
Spain.
Figure 3.2 Folded
and faulted
extremely strong
Devonian
radiolarian chert
interbedded with
thin bands of
extremely weak
organic shale, near
Cabacés, Spain.
speci
cally tuned to the project. The process is illustrated simply in
Figure 3.4
and expanded upon later in this chapter. One of the key
features of many ground models is differentiating between upper,
soil-like materials, and underlying rock, with the separating bound-
ary being called rockhead or, sometimes,
engineering rockhead
.
'
'
ni-
tions and connotations and is sometimes used in an over-simplistic
way for what is a complex situation. The consequences of wrong
perception can be severe if, for example, soil is encountered at depth
and below the water table, unexpectedly in a hard rock tunnel.
De
Care must be taken in using this term because it has various de
nitions of rockhead are set out in
Box 3-1.
