Engineering geology aspects for design and classification - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 31

2. Interface structure
Layout
Spatial alignment, which is described by the angles of strike and dip (in a sphere dia-
gram or joint rose)
Spacing of parallel interfaces (frequency)
Extent (degree of jointing)
Opening width
Filling of the individual joints (for example mylonite, calcite, quartz)
Unevenness and roughness of the interfaces

3. Formation water conditions
Level of the groundwater table
Rock permeability, flow direction and seepage water quantities to be expected in the
rock cavity
Chemistry of the formation water (for example concrete aggressivity)
Investigation methods. There are various methods of investigating the engineering
geological conditions, which can generally also be used for rock mechanical investiga-
tions and have therefore been developed in close cooperation between rock mechanics
and engineering geology specialists. Direct methods of investigation (for example natu-
ral openings, ground movements, boreholes) and indirect investigation methods (me-
chanical and optical methods) can be differentiated. The most important processes are
described in Table 2-4 and Table 2-5. For further descriptions, scope of application, in-
formation content and discussion, reference should be made to the work of Kany [102].
Boreholes are especially useful for rock mechanics investigations, so the information
that can be gained from the drilling data, samples and the borehole is described in more
detail in Table 2-5.

Table 2-4 Engineering geology investigation methods, from M. Kany [102].

Direct investigation methods Indirect investigation methods

Process Example Process Example

Natural investigations Walking the terrain,

aerial photography

Evaluation of existing
documentation,
surface mapping

Ground movement Rock opening,

test pits,
Investigation tunnels
and shafts,
Test excavation in large
or full profile

Mechanical methods Penetration test

Drilling Rotary drilling (with core

extraction)

Optical methods Optical sounding,

Photographic sounding,
TV sounding

Geophysical methods Seismology,

Geoelectrics