Page 597 - Rock Mechanics For Underground Mining

AVAILABLE SUPPORT LINE CALCULATIONS

Support stiffness

1 s c s 4l
= + Q
2
k b r i d E b
b
Maximum support pressure

T bf
p sb max =
s c s
C.3.4 Available support line for a single support system
If k is the stiffness of the support system, p s max is the maximum support pressure that
the system can provide, and i0 is the radial tunnel deformation before installation of
the support, then for p i < p s max , the available support line is given by

i i0 p i
= +
r i r i k
C.3.5 Available support line for combined support systems

Input data

k 1 = support stiffness of system 1;
p s max 1 = maximum support pressure for system 1;
k 2 = support stiffness of system 2;
p s max 2 = maximum support pressure for system 2;
i0 = initial tunnel deformation before installation of support.
(The two systems are assumed to be installed simultaneously.)

Available support line

r i p s max 1
(1) max 1 =
k 1
r i p s max 2
(2) max 2 =
k 2
r i p i
(3) 12 =
(k 1 + k 2 )

(4) For 12 < max 1 < max 2
i i0 p i
= +
r i r i (k 1 + k 2 )

(5) For 12 > max 1 > max 2
max 1 (k 1 + k 2 )
p max 12 =
r i
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