Tunnel Probabilistic Structural Analysis Using the FORM
Table 4
Results of the reliability analysis of tunnel stability, considering the joints strength parameters (C, φ, Ten) as the independent random variables (scenario 2).
Block code (BC)
FORM analysis
Monte-Carlo simulation
Reliability index ()
Probability of failure () %
Calculation time (sec)
Function iterations
Iterations (~needed)
Probability of failure () %
Simulation time (sec) (~needed)
Actual
0 0 0
—
—
—
—
—
—
—
—
0 0 1
3.838
6.19 × 10−3
10.6
58
~1.62 × 106
N-A
~2.82 × 105
N-A
0 1 0
10.320
2.76 × 10−23
9.4
57
~6.61 × 1026
N-A
~1.15 × 1026
N-A
1 0 1
1.569
5.8
8.5
52
2000
5.5
348
0.093
1 1 0
2.021
2.17
9.7
52
5000
2.01
890
0.099
1 1 1
0.066
47.4
10.6
67
600
47.5
104.9
0.043
: calculation (simulation) time using a 2.67 GHz, core i5 processor. : it is not possible to calculate in reasonable time period with ordinary processing units.