Table 3. An example of rock mass and tunnelling improvements that might be achieved by pre-injection with state-of-the-art, fine, cementitious multi-grouts in a typical rock mass of rather poor quality. (See Barton 2000b details)
Before pre-grouting
After pre-grouting
Q = 0.8 (very poor)
Q = 16.7 (good)
Qc = 0.4
Qc = 8.3
Vp = 3.1 km/s
Vp = 4.4 km/s
Emass = 7 GPa
Emass = 20 GPa
Sigmacm = 9 MPa
Sigmacm = 25 MPa
Pr = 13.6 t/m2
Pr = 4.9 t/m2
L = 2.5
L = 0.1
K = 2.5 10-7 m/s
K = 10-8 m/s
D = 25 mm
D = 1 mm
FC = 14?
FC = 63?
CC = 1.7 MPa
CC = 8.3 MPa
B 1.6m c/c
B 2.4m c/c
S(fr) 10 cm
None
Note : Qc = Q x _c/100, and _c assumed equal to 50 MPa.
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