Empirical relation between damage extent for circular openings may be used for other profiles when dimensions are converted. 3.Lacking data may be ...
Stochastically determined safety of underground structures according to Eurocode Lauri Uotinen, Rockplan Topias Siren, Rockplan Riitta Lehmusjärvi, Posiva Oy
Rock Engineering Seminar 4.11.2009
n
σsm,max σsm,rnd
n
σθ,min Monte Carlo Casino
σθ,max σθ,rnd
Class
Example (modified)
KFI
CC3 high
Nuclear power plants, railway stations, sports and public spaces, factories
1.1
CC2 Everything else medium CC1 low
Temporary tunnels and shafts, vertical shafts, water tunnels (low p), research tunnels, pilots
1.0
0.9
Design assumptions in spalling analysis:
1.Spalling strength of rock mass is 57 % of uniaxial compressive strength of rock sample 2.Empirical relation between damage extent for circular openings may be used for other profiles when dimensions are converted 3.Lacking data may be represented with triangular distribution without significant loss of reliability 4.Lower and upper 5 % fractiles of uniaxial compressive results may be removed to eliminate unrealistically low and high results
Design assumptions are in wedge stability analysis:
1.The in situ field stress is not included in the analysis 2.The water pressure is not taken into account 3.The joint length was restricted to 10 m
σH 10º
σH 90º
n
σθ
n = 10 000 pseudo random pairs σsm σ n
From stochastic analysis: Spalling probability 15 % Mean safety factor 1.33 Nominal damage depth 0.00 m (for comparison) From mean analysis: Spalling probability N/A Mean safety factor 1.33 Nominal damage depth 0.00 m
dk
Area depth -368 m Spalling probability 43 % Mean factor of safety 1.05 Nominal damage depth 0.00 m → No actions are required, minimal damage may be expected.
Area depth Spalling probability Mean factor of safety Nominal damage depth → No actions are required.
-363 m 12 % 1.38 0.00 m
Area depth Spalling probability Mean factor of safety Nominal damage depth → No actions are required.
