Abstract Tunnel face is often prone to collapse accidents. In order to evaluate its active stability effectively, a three-dimensional (3D) multi-sliders failure mechanism of tunnel face is constructed. Then, the upper bound analysis of 3D active stability of a shallow tunnel face is carried out based on the strength reduction method. Combined with upper bound limit analysis method, the objective function of the safety factor is established, and optimal upper bound solution of the safety factor is obtained based on nonlinear optimization program. The effectiveness of this proposed method is proved by comparative analysis. Meanwhile, the effects of different parameters on the safety factor and failure modes are analyzed. Results show that the safety factor FS increases linearly with the increase of cohesion c and internal friction angle φ, but it decreases with the increase of ground surcharge σs and soil gravity density γ, and decreases nonlinearly with the increase of overload ratio C/D. The effects of overload ratio C/D and internal friction angle φ on the active failure modes are significant, while cohesion c, ground surcharge ss and soil gravity density γ are insignificant. When active failure zone of is not reaching to ground surface, overload ratio C/D and ground surcharge ss have no influence on the calculated results.
Abstract：
Tunnel face is often prone to collapse accidents. In order to evaluate its active stability effectively, a three-dimensional (3D) multi-sliders failure mechanism of tunnel face is constructed. Then, the upper bound analysis of 3D active stability of a shallow tunnel face is carried out based on the strength reduction method. Combined with upper bound limit analysis method, the objective function of the safety factor is established, and optimal upper bound solution of the safety factor is obtained based on nonlinear optimization program. The effectiveness of this proposed method is proved by comparative analysis. Meanwhile, the effects of different parameters on the safety factor and failure modes are analyzed. Results show that the safety factor FS increases linearly with the increase of cohesion c and internal friction angle φ, but it decreases with the increase of ground surcharge σs and soil gravity density γ, and decreases nonlinearly with the increase of overload ratio C/D. The effects of overload ratio C/D and internal friction angle φ on the active failure modes are significant, while cohesion c, ground surcharge ss and soil gravity density γ are insignificant. When active failure zone of is not reaching to ground surface, overload ratio C/D and ground surcharge ss have no influence on the calculated results.
JIANG Wujun1 LI Dejian2,
3 QU Tuoyu3
.Upper Bound Analysis of Three-Dimensional Active Stability of a Shallow Tunnel Face Based on the Strength Reduction Method[J] MODERN TUNNELLING TECHNOLOGY, 2020,V57(6): 55-62
2020, Vol. 57 