Analysis, design and construction - Practical Engineering Geology - page 307

Drive North

minor overbreak

II/III

infill variable
10 to 100 mm
mostly granular/
lithic fragments,
some clay

will probably appear in roof in next
pull

60/188

45/040 v. weak zone. probably

due to coalescing shear
zones. soft sandy clay +
gravel (rock fragments)

approx.
60/194 III

III

TIE RODS

III

v. weak,
soft. clay in part

C L

1 metre

FACE FACE FACE

0

0.5

1.0

1.5

2.0

boarded

2.5 m

FOOT
LEFT
WALL

FOOT
RIGHT
WALL

ROCK TYPE DETAILS ADDITIONAL NOTES

v. weak zone in lower part of left
wall and across face. soft clay in
part. Thick zones up to 0.5 m are
at intersects of infilled joints. One
dipping south (194), up into face
has softened up invert 1.5 m back
from face. Possibly will cause
overbreak on next pull.

NAME GRANITE

COLOUR Pink, mostly discoloured brown

STRENGTH moderately strong. locally strong/ mod. weak

WEATHERING III occ. II

JOINT DETAILS mostly 300 mm, incipient closer

Generally tight

DIPS/
AZIMUTHS

Several major infilled discontinuities/shear
zones. also minor clay infilled

WATER INFLOW

Damp, no inflow

CHAINAGE
AGREED RECORD
WH
SH

95.94
15.9.89

ADD COMMENTS

Figure 6.33 Example of agreed record of ground conditions in a tunnel. Queens Valley Reservoir
diversion tunnel, Jersey, UK.