Civil Engineering Reference
In-Depth Information
Civil engineering applications
14.1 Introduction
When a slope above an important civil engineer-
ing structure is found to be unstable, an
urgent decision is commonly required on effective
and economical remedial measures. Evidence of
potential instability includes open tension cracks
behind the crest, movement at the toe, failures
of limited extent in part of the slope, or failure
of an adjacent slope in similar geology. Whatever
the cause, once doubt has been cast upon the sta-
bility of an important slope, it is essential that
its overall stability should be investigated and, if
necessary, appropriate remedial measures imple-
mented. This chapter describes five rock slopes on
civil engineering projects in a variety of geological
and climatic conditions, and the slope stabiliza-
tion measures that were implemented. For each
example, information is provided on the geo-
logy, rock strength and ground water conditions,
as well as the stability analysis, design of the
remedial work and construction issues.
The purpose of these case studies is to describe
the application of the investigation and design
techniques
b
=70
°
H
b
=20m
Z
= 18.8 m
H
c
=60m
p
=35
°
f
=50
°
Figure 14.1
Geometry assumed for two-dimensional
plane failure analysis of the slope in Case Study I.
in a nearby slope has caused attention to be
focused on this particular cut and concern has
been expressed that a major slide could occur
resulting in serious damage to an important civil
engineering structure at the foot of the cut. An
assessment was required of the short- and the
long-term stability of the cut, and recommend-
ations for appropriate remedial measures, should
these prove necessary. No previous geological or
engineering studies had been carried out on this
cut, and no boreholes were known to exist in
the area. The site was in an area of high rainfall
intensity and low seismicity. A horizontal seis-
mic coefficient,
a
H
of 0.08
g
had been suggested
as the maximum to which this cut was likely to
be subjected.
described
in
previous
chapters
of
the topic.
14.2 Case Study I—Hong Kong: choice of
remedial measures for plane failure
14.2.1 Site description
14.2.2 Geology
A 60 m high cut had an overall face angle of
50
◦
, made up of three, 20 m high benches with
face angles of 70
◦
The cut was in slightly weathered granite
containing several sets of steeply dipping joints,
(Figure 14.1). A small slide
