Geoscience Reference
In-Depth Information
•
Persistence is difficult to judge from borehole data, and needs to be reassessed
during construction.
Table 18.4
Effect of discontinuities (Bieniawski, 1989).
Parameter
Range of values
Discontinuity
Spacing
2 m
0.6-2 m
200-600 mm
60-200 mm
60 mm
>
<
Rating
20
15
10
8
5
Discontinuity
Surfaces
Very rough
Rough
Slightly rough
Smooth
Slickenslided
condition
6
5
3
1
0
Persistence
1 m
1-3 m
3-10 m
10-20 m
20 m
<
>
6
4
2
1
0
Separation
None
0.1
0.1-1 mm
1-5 mm
5mm
<
>
6
5
4
1
0
Infilling
None
Hard filling
Hard filling
Soft filling
Soft filling
(Gouge)
5mm
5mm
5 mm thick
5mm
<
>
<
>
6
4
2
2
0
Weathering
FR
SW
MW
HW
XW
6
5
3
1
0
Rating
30
25
20
10
0
18.5 RMR - groundwater
•
The groundwater flow would be dependent on the discontinuity (eg persistence
and separation).
Table 18.5
Effect of groundwater (Bieniawski, 1989).
Parameter
Range of values
Groundwater
Inflow per 10 m tunnel
None
<
10
10-25
25-125
>
125
length (m)
Joint water pressure/
0
<
0.1
0.1-0.2
0.2-0.5
>
0.5
Major principal axis
General conditions
Completely dry
Damp
Wet
Dripping
Flowing
Rating
15
10
7
4
0
18.6 RMR - adjustment for discontinuity orientations
•
The discontinuity arrangement effect is based on the type of construction.
Table 18.6
Rating adjustment for discontinuity orientations (Bieniawski, 1989).
Parameter
Range of values
Strike and dip of
Tunnels and mines
0
2
5
19
12
−
−
−
−
discontinuities
Foundations
0
−
2
−
7
−
15
−
25
Slopes
0
5
25
50
60
−
−
−
−
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