| With the increasing demand for tunnel construction,a large number of highway tunnels need to be built in water-rich areas.At present,“plugging groundwater and limiting drainage”is the water control concept of water-rich tunnel,which requires engineers to fully consider the water pressure resistance of tunnel structure.At present,the anti-water pressure structure of tunnel is often limited to“primary support+secondary lining”,but in fact,this single anti-water pressure structure can not guarantee the long-term safety of tunnel.Based on the Chuntianmen Tunnel of Nanliang Road,this thesis uses theoretical analysis,literature research and numerical simulation to study the anti-water pressure structure and safety of highway tunnels in water-rich areas.The main work and research conclusions are as follows:（1）The high water pressure failure cases of water-rich highway tunnels in China in recent years were investigated and analyzed,and the source and occurrence form of groundwater in water-rich tunnels were revealed.The main forms and causes of high water pressure damage are summarized.（2）The composition and characteristics of anti-water pressure structure are expounded,and the role of grouting ring in water plugging and decompression is summarized.The initial support and grouting ring jointly ensure the safety of the tunnel construction period;the tunnel drainage network system plays the role of discharging and dredging groundwater,and the secondary lining bears the water pressure caused by environmental changes and poor drainage.Under the“plugging groundwater and limiting drainage”,the water-rich tunnel should combine the above four parts as a water pressure resistance structure;the accuracy of FLAC3D numerical model is verified by comparing the theoretical analytical solution of tunnel water load,the existing seepage test value and the numerical solution.（3）The effect of water plugging and decompression of grouting ring under different grouting parameters and plugging methods was studied by numerical simulation.The results show that the grouting circle has the effect of water plugging and decompression only when the tunnel drainage is considered.Increasing the thickness of grouting ring or reducing its permeability coefficient can enhance its water plugging and decompression effect,which is reflected in the reduction of tunnel seepage flow and water load of supporting structure.With the enhancement of its water plugging and decompression effect,the external water pressure and internal force of the lining structure are reduced,and the reduction effect of the internal force at the lining invert is the best,reaching 50%～60%.When the thickness of grouting ring is 5m and the permeability coefficient ratio is 1/50,it can resist 55%～60%water pressure.At this time,the effect of water plugging and decompression is better and more economical.（4）The influence of initial support parameters on water load and safety was studied.The results show that the initial support can cooperate with the grouting ring to further play the role of water plugging.The decrease or increase of the permeability coefficient of the initial support can increase the external water pressure of the initial support,reduce the seepage flow and improve the structural safety.（5）The“load-structure”model is used to analyze the anti-water pressure lining structure under full-section pressure,and the stress characteristics and safety of the lining structure are obtained.The results show that under the principle of’safe and practical,reliable quality,economical and reasonable’,the lining structure designed according to the water pressure level meets the design requirements,and the lining should be designed according to the water pressure of the water-rich section.The lining structure is in the state of full section compression.The bending moment and axial force at the arch foot are the largest,and the safety factor is the smallest,which is the weakest part of the structure.The nearly circular lining structure can withstand external water pressure well.（6）The numerical model is established by ANSYS finite element software to study the stress characteristics and safety of lining structure under local pressure.The stress characteristics and safety of lining structure under different simplified forms of water pressure and water pressure are obtained.The results show that the simplified form of water pressure has a significant influence on the local internal force of lining,and its simplified form should correspond to the connectivity of the cavity containing water.When the lining vault is locally pressurized,the negative bending moment appears at the vault and inverted arch,and the internal force is symmetrically distributed,with the lowest safety.The lining stress is more unfavorable under asymmetric local circumferential water load.The safety control measures of anti-water pressure structure are put forward,and the effect of“dynamic decompression”of the pressure relief system is discussed. |
