Study On Soft Rock Large Deformation Control Measures For Newly Built Manmo 2 Tunnel Of Yumo Railway

This article takes the Yumo Railway Manma No.2 tunnel project as the research background,combines the actual situation on the site,and analyzes the previous research on the basis of the large deformation.The reason for the deformation under specific geological conditions is proposed,and the field measured data and numerical simulation are combined.In contrast,research on large deformation control measures.The effects of excavation methods and grouting of small catheter pipes on deformation control were mainly analyzed.The thesis mainly studies the following:(1)Based on the on-site monitoring and the nature of the surrounding rock in front of the palm face,the geological conditions that caused the large deformation were analyzed.Combined with the specific construction situation of the large deformation section of the Manme 2 tunnel,the reason for the large deformation may be that the soft rock has rheology and the surrounding rock stress rebalances after the tunnel is excavated,and the surrounding rock reaches a damaged state,which results in the initial support of the tunnel.Cracking.(2)Through numerical simulation,the tunnel displacement,shotcrete stress,steel frame stress,palm surface extrusion deformation,and equivalent plastic area of the tunnel under two different excavation methods are calculated and compared.Advantages and disadvantages of the two excavation methods.It is concluded that the spray concrete stress increases with the advancement of the palm surface and the passage of time.The sprayed concrete is stretched at the arch top,the left and right arch waists are basically compressed,the left and right maximum spans,and the two-step method is compressed.The three-step method is pulled,and the left and right side walls are pulled.The arch steel arch frame is mainly tensile.The tensile stress of the arch steel arch frame has been increasing with the advancement of the palm surface,and the tensile stress of the two-step method has always been greater than that of the three-step method.Two curves The trends are basically the same.The stress of the two-step steel arch is always greater than that of the three-step steel arch.(3)The equivalent plastic strain zone of the surrounding rock in the cross section has been increasing from the right arch waist to the maximum span,and has decreased from the maximum span to the foot of the wall.Under two different excavation methods,the equivalent plastic strain zone range of the two-step surrounding rock is smaller than that of the three-step surrounding rock.The strain range of the equivalent plastic zone of the longitudinal surrounding rock increases with the advancement of the palm face.(4)By calculating the influence of the step height on the tunnel displacement,it is obtained that when the height of the step is between 3.24 m and 4.32 m,the slope of the maximum horizontal displacement curve of the tunnel is greater than the slope of the vertical maximum displacement curve.When the height of the step is 4.32m-At 5.4m,the slopes of the two displacement curves are gentle.When the height of the upper step is between 5.4m and 6.48 m,the slope of the maximum horizontal displacement curve is greater than the slope of the vertical displacement curve,indicating that the excavation height of the upper step has a greater effect on the horizontal deformation of the tunnel.influences.Based on the analysis of the displacement values of each measuring point,it is appropriate to take a step height of 5.4m.By calculating the relationship between the different excavation footage and deformation of the tunnel,it can be obtained that the tunnel deformation can be better controlled when the excavation footage of this tunnel is controlled from 0.5m to 1m.(5)Based on the two-step excavation method,the effect of grouting ahead of small ducts on the large deformation control of the tunnel is analyzed,and it is obtained that the subsidence value of the vault decreases as the length of the small ducts increases.When the length is less than 4 ~ 6m,the slope of the dome settlement curve is large;when the length of the small duct is greater than 4.5m,the change value of the settlement curve of the dome is small,which indicates that the small duct length is 4 ~ 5m,which is more suitable for this project.When the length of the small catheter was increased from 3m to 4m,the left arch waist displacement value decreased by 0.9mm,and the right arch waist displacement value decreased by nearly 1.4mm.Comprehensive analysis shows that the optimal length of the small lead catheter is 4m ~ 5m.When the length of the small duct is increased from 3m to 4m,the maximum principal stress of the lining is reduced by 0.26%;when the length of the small duct is increased from 4m to 4.5m,the maximum principal stress of the lining is reduced by 0.13%;the length of the small duct is increased from 4.5m to 5m As a result,the maximum principal stress of the lining was reduced by 15%.From different angles of circumferential grouting,it can be concluded that when the grouting range is 90 ° to 120 ° degrees,the slope of the vertical displacement curve is relatively large,indicating that the effect of the advance grouting small catheter is more obvious,and the slope change of the horizontal displacement curve is also compared.Big.When the grouting range is 120 ° ~ 150 °,the slope of the vertical displacement curve is large.When the grouting range is from 150 ° to 180 °,the rate of change of the vertical displacement curve is relatively small.(6)Due to the complexity of the large deformation of the tunnel and the current status of research at home and abroad,according to the actual situation of the large deformation section of the Manme 2 tunnel,the design grading standards are mild to moderate,severe,and severe.According to the amount and rate of deformation during the construction stage,it is divided into ?,?,and ? grades.