Abstract:

The failure mode of shallowburied asymmetricallypressured tunnel with large span is studied in the paper. The plastic strain and safety factor of triplecenter curved wall tunnel and horseshoe shaped tunnel under different depths and slope ratios are analyzed by finite element strength reduction method. Some conclusions are drawn as follows: 1) When the tunnel is under normal pressure condition, the maximum plastic strain of triplecenter curved wall tunnel transfers from the arch to tunnel sidewall with the burial depth increase. When the tunnel is shallowburied, the fracture surface of horseshoe shaped tunnel transfers from the arch and sidewall to wall feet with the burial depth increase. 2) When the tunnel is under asymmetricallypressured condition, the failure firstly occurs in tunnel shallow buried side, and the maximum plastic strain of triplecenter curved wall tunnel transfers from the arch to sidewall with the burial depth increase. The fracture surface of horseshoe shaped tunnel transfers from the arch of the tunnel shallowburied side and sidewall of the deepburied side to the tunnel wall feet with the burial depth increase. 3) The safety factor of triplecenter curved wall tunnel is larger than that of horseshoe shaped tunnel under same buried depth.

Key words: shallowburied asymmetricallypressured tunnel, large span, finite element strength reduction method, burial depth, slope ratio, safety factor