ZHANG Zhi-guo, LUO Jie, ZHU Zheng-guo, et al. Stability of shield tunnel excavation face under seismic action based on upper bound theorem of limit analysis[J]. 2024, 45(4): 1201-1213.
ZHANG Zhi-guo, LUO Jie, ZHU Zheng-guo, et al. Stability of shield tunnel excavation face under seismic action based on upper bound theorem of limit analysis[J]. 2024, 45(4): 1201-1213.DOI: 10.16285/j.rsm.2023.0626.
The coupling effect of layered soil characteristics and seismic action is rarely considered in the studies on the stability of shield tunnel excavation face. In this study
a three-dimensional logarithmic spiral failure model of shield tunnel excavation face considering seismic action in layered soil is constructed for study. Firstly
the dynamic response caused by earthquake is reduced to the inertia force in horizontal and vertical directions using pseudo-static method. Secondly
the three-dimensional logarithmic spiral failure mechanism
initially designed for homogeneous soil
is improved to be suitable for layered soil. Then
according to the upper bound theorem
the power of seismic inertia force is introduced into the virtual power equation to derive the upper bound solution of the support force of shield tunnel excavation surface considering the soil stratification characteristics and seismic action conditions. Finally
the theoretical upper bound solution is compared with the 3D numerical simulation results
engineering measured results and existing experimental results
showing good agreement. Furthermore
the key physical characteristics are analyzed according to the horizontal seismic acceleration coefficient and formation thickness. The results show that when the proportional coefficient ζ > 0
the ultimate supporting force increases significantly with the increase of horizontal earthquake acceleration coefficient. Conversely
when ζ < 0
the increasing trend of ultimate supporting force decreases with the increase of horizontal earthquake acceleration coefficient. Additionally
when horizontal earthquake acceleration coefficient kh=0
that is
in the absence of earthquake action
the normalized ultimate supporting force does not change with the change of proportion coefficient ζ . Moreover
in the hard above and soft below layered soil
an increase in the thickness ratio of the lower soil layer leads to an increase of the ultimate supporting force. In contrast
in the soft above and hard below layered soil
an increase of the thickness ratio of the lower soil layer results in a decrease of the ultimate supporting force.