Engineering geology aspects for design and classification - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 45

Table 2-12 continued

Desc ription Range of values J a φ r (approx.)

(b)
F

Rock wall contact before 10 cm shear
sandy particles, unbonded disintegrated rock without
clay
strongly over-consolidated, non-softening clay mineral
filling (continuous, < 5 mm thick)
medium or weakly over-consolidated, softened clay
mineral filling (continuous, < 5 mm thick)
swelling clay filling, for example montmorillonite (con-
tinuous, < mm thick). The value of J a depends on the
content by percent of clay-type minerals susceptible to
swelling and the ingress of water.
No rock face contact in the shear jointing
zones or drifts with disintegrated or crushed rock and
clays (compare also G, H and J for the clay description)
zones or bands of silty or sandy clays, small clay frac-
tions (non-softening)
thick, continuous zones or bands of clay (compare also
G, H and J for the clay description)

4.0 25 to 30°

G 6.0 16 to 24°

H 8.0 12 to 16°

J 8.0 to 12.0 6 to 12°

(c)
K

6.0, 8.0 or
8.0 to 12.0
5.0

6 to 24°

L

M 10.0, 13.0 or

13.0 to 20.0

6 - 24°

Note: (i) The values for φ r should be regarded as approximate reference values for the
mineral properties of the altered products, in case such are present.

Table 2-13 Q System: Joint water parameter - J w .

Description J w Approximate

water pressure
[kg/cm²]

Note

A Dry excavation or slight water ingress up

to 5 l/min
Medium water ingress or pressurised
water loss of individual joints
Heavy water ingress or high pressure in
stable rock mass with unfilled joints
Heavy water ingress or high pressure,
considerable water loss from individual
joints
Exceptionally heavy water ingress or
water pressure after blasting, which
declines with time
Exceptionally heavy water ingress
or persistent water pressure with no
noticeable reduction

1.0 < 1 (i) The values

for cases C-F
are coarse
estimates.
Increase J w in
case dewater-
ing measure-
ments are
available.
(ii) Special
problems
caused by
ice formation
have not been
considered.

B 0.66 1.0 to 2.5

C 0.5 2.5 to 10.0

D 0.33 2.5 to 10.0

E 0.2 to 0.1 > 10.0

F 0.1 to 0.05 > 10.0