Analysis, design and construction - Practical Engineering Geology - page 267

typical tunnelling hazards to be considered during construction is
presented in a table in Appendix E-3.

6.6 Slopes
Landslides cause major economic damage and kill many people each
year. Slopes can be split into natural and man-made. The hazards from
natural terrain landslides in mountainous regions and at the coast are
considered in Chapter 4.
Man-made slopes include cut slopes (cut into the natural hillside)
and

fill slopes. Fill slopes might simply comprise the excess debris from
an adjacent cutting, dumped or compacted onto the adjacent hillside to
form an extra carriageway, but can also include sophisticated, high
and steep slopes incorporating geotextiles or other materials to
strengthen the soil ( Figure 6.21) . Stability needs to be assessed by
engineers and if considered unstable, measures must be taken to
improve the stability to an acceptable level.

6.6.1 Rock slopes
Rock slope stability is generally controlled by the geometry of pre-
existing, adversely oriented discontinuities, including bedding planes,
faults and master joints including sheeting joints. Failure types can be
grouped as illustrated in Figure 6.22 and as follows:
Shallow: super cial failures, generally low to medium volume.

Structurally controlled: sliding may occur on one or more intersecting
discontinuities that are adversely oriented relative to the slope geome-
try. Toppling can result because of the presence of unstable columns

Figure 6.21
Construction of
reinforced earth
embankment for
Castle Peak Road
widening, Hong
Kong.