BayofMines
Mining
Read a report about tunneling in weak ground which models the tunnel failure by use of the Duncan Fama model.
This basically states that failure occurs when internal support pressure (Pc) < Critical Support Pressure (Pcr). That makes sense.
The part I am having trouble with is the calculation for critical support pressure.
Pcr = (2*(hydrostatic stress, Po)- (UCS of rockmass)) / (1+K)
This works out that an INCREASE in rock strength will result in DECREASE in the critical support pressure. Another way to put this is that an increase in rock strength is more likely to result in failure. What gives? What do I not understand about this?
Regards and thanks for anyones help.
This basically states that failure occurs when internal support pressure (Pc) < Critical Support Pressure (Pcr). That makes sense.
The part I am having trouble with is the calculation for critical support pressure.
Pcr = (2*(hydrostatic stress, Po)- (UCS of rockmass)) / (1+K)
This works out that an INCREASE in rock strength will result in DECREASE in the critical support pressure. Another way to put this is that an increase in rock strength is more likely to result in failure. What gives? What do I not understand about this?
Regards and thanks for anyones help.
