| Groundwater problems are common in tunnel engineering,especially for mountain tunnels in high water pressure and water-rich areas.The safety impact of groundwater seepage on the whole tunnel project is particularly important.Based on the Maanshan tunnel project of Zhongyu Expressway in Shuyang County,Chongqing,this paper studies the effects of different head heights and different grouting parameters on the seepage field of tunnel lining by finite element numerical simulation.The seepage-stress coupling analysis studied the effects of different head heights,different grouting ring parameters and different lining thicknesses on the stress and deformation of the tunnel lining structure.The main contents of this paper are as follows:(1)Using Midas/GTS finite element software to analyze the seepage field of tunnel lining under different head height and different grouting parameters,the variation law of external water pressure of tunnel lining structure is obtained.The results show that the height of the head increases and lining The external water pressure also increases;when the thickness of the grouting ring is increased,the external water pressure of the lining decreases;the external water pressure of the lining decreases as the permeability coefficient of the grouting ring decreases,and the grouting is reduced.The ring permeability coefficient is the most effective way to reduce the external water pressure of the lining structure.(2)Using the analysis method of stress field and seepage field coupling,the vertical effective stress of the tunnel lining and the horizontal effective stress are compared and analyzed.The parameters of the Maanshan tunnel at different head heights and different grouting loops are different.The stress characteristics of the lining structure under the thickness of the lining show that the stress in the vertical direction is the largest,the stress in the arch is the largest in the horizontal direction,the height of the head is increased,the effective stress in the vertical direction of the lining structure and the effective stress in the horizontal direction.It is also increasing,but the rate of increase is decreasing;the thickness of the grouting ring is increased,the effective stress in the vertical direction of the lining structure and the effective stress in the horizontal direction are decreasing,but the decreasing range is decreasing;the permeability coefficient of the grouting ring is decreasing,and the lining structure is decreased.The effective stress in the vertical direction and the effective stress in the horizontal direction decrease at the acceleration;the thickness of the second lining increases,and the effective stress in the vertical direction of the lining structure and the effective stress in the horizontal direction decrease,but the rate of decrease decreases.(3)By establishing the coupled model of seepage stress,the additional deformation of Maanshan tunnel lining structure under water pressure during operation is analyzed,and the deformation law of lining structure under different head height,different grouting ring parameters and different lining thickness conditions are discussed respectively.The calculation results show that with the rising groundwater level,the deformation of the tunnel lining structure will always increase.The ability to timely control the groundwater level is a key measure to ensure the stability of the tunnel structure during the operation of the tunnel;increasing the thickness of the grouting ring and the thickness of the lining can be effective.Decreasing the deformation displacement value of the lining structure,but not as thick as possible;reducing the permeability coefficient of the grouting ring is an effective method to reduce the deformation displacement value of the lining structure.The smaller the permeability coefficient of the grouting ring,the more the deformation of the lining structure will be.small.(4)The numerical analysis of the external water pressure and deformation of the tunnel lining structure is carried out,and the design parameters of the Ma’anshan tunnel are optimized to provide reference for similar projects. |
