The effect of the intermediate principal stress on the ground response of circular openings in rock mass

Analytical solutions are presented for stress distributions, displacement distribution, and the extent of the plastic zone of a circular opening with a finite external radius subjected to uniform pressures acting on the internal and external boundary surfaces under plane strain conditions. The results show that the intermediate principal stress has an influence on the ground response curve, the stress distributions, the extent of the plastic zone, and wall displacement of the tunnel. It was found that Frenner's formula and Kastner's formula give the largest and the second largest extent of the plastic zone. The intermediate principal stress effect of rock mass should be taken into account in order to get an accurate prediction of response of a tunnel.