| With the acceleration of urbanization,the role of urban subway in urban traffic is becoming more and more important.The subway construction and layout in the developed areas of our country have been relatively perfect.In recent years,the development of subway has gradually shifted from the important cities in developed areas to the relatively backward southwest region,and the planning and construction of subway lines in various cities in the southwest region have been developed to a certain extent,including Guiyang,which is relatively backward in economic development.Guiyang is a typical karst landform,its topography and environment are more complex,the urban layout is compact,resulting in its difficult construction characteristics,encountered engineering problems are not completely comparable similar projects,for the solution In order to solve the difficult problem of subway station construction in the complex environment of Guiyang area,the influence of mechanical characteristic law and surrounding rock stability of the excavation scheme of the station project is obtained by means of theoretical analysis,model test,numerical calculation and field monitoring data.The main findings are as follows:(1)By using the modified span of natural balance arch,the calculating formula of maximum downward displacement mass weight of rock column theory is analyzed.(2)Through the experimental study of the excavation model of reserved middle rock pillar tunnel,the stress distribution of surrounding rock is analyzed.During the excavation of the two sides of the tunnel,the stress of the side wall and the surrounding rock roof of the tunnel increases slowly from 0?1 k Pa.Combined with the test results,it is concluded that the reserved middle rock column plays an important role in tunnel stability.(3)Based on the numerical simulation of the tunnel excavation scheme of the reserved middle rock column,the influence of the middle rock column on the tunnel stability is analyzed from the angle of surface subsidence,vault settlement,horizontal displacement of side wall and middle rock column.The removal length of the middle rock column should not be greater than 40 m,and the value should be in the range of 20-30 m.(4)For studying the influence of different buried depth on the arch-forming effect of tunnel,the width of middle rock column is 0.3 times that of tunnel span.Six groups of tunnel buried depth data are taken to represent different overlying soil pressure,and the mechanical characteristics ofdifferent buried depth on middle rock column are analyzed.It is concluded that when the buried depth is in the range of 0.75 W-1.0W,the plastic deformation of middle rock column is small,and the middle rock column can basically realize self-stability.For more than one W of buried depth,the plastic deformation of the middle rock column and the surrounding rock of the tunnel is obviously increased.At this time,we should focus on monitoring the deformation of the middle rock column and surrounding rock,increase the frequency of measurement,and do a good job of strengthening the middle rock column,such as grouting reinforcement before the use of pre-reinforcement.Stress anchor reinforcement.(5)Through the field monitoring and numerical simulation of practical engineering,it is pointed out that the reserved middle rock column plays an important role in controlling the deformation of the surrounding rock of the tunnel.The data show that the deformation monitoring value of the tunnel increases after excavation,but the deformation value of the tunnel is within 10 mm and meets the minimum control value of 20 mm.. |
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