| Northwest is located in the loess area,during the road construction process,in order to meet the road line shape and other requirements,has built a lot of loess tunnels.However,our country’s current highway and railway tunnel design specifications for the loess tunnel rock classification is very rough,which can not meet the requirements of engineering design and construction.This article relies on Yan-Yan expressway engineering,the statistical analysis method is used to study the classification index of surrounding rock of loess tunnel,threedimensional numerical simulation method is used to analyze the deformation law of surrounding rock during excavation of loess tunnel under different surrounding rock conditions,the main conclusions are summarized as follow:(1)Comparing and analyzing the differences between the physical and mechanical properties of the old and new loess,comparing the variability of physical and mechanical parameters of loess.(2)By using correlation analysis,cluster analysis and principal component analysis,nine physical indexes of loess were grouped.according to the results of grey relational analysis,and considering the influence of loess joints on the structural integrity of loess,the natural moisture content,dry density,plasticity and elastic wave velocity of the rock mass are selected as the grading indexes of the surrounding rock of the loess tunnel.(3)The vertical displacement,surface subsidence,horizontal displacement and distribution of plastic zone of surrounding rock caused by excavation of loess tunnel under different surrounding rock conditions are analyzed by using the FLAC3 D software,and putting forward some advices for support of loess tunnel’s excavation.The classification scheme of the surrounding rock of the loess tunnel proposed in this paper is reasonable,and it has some reference value and significance for the division of the surrounding rock in the loess area. |
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