Study On The Harm And Defence Of The Voids Behind Lining In The Shallow Mountain Tunnel

The voids behind the tunnel lining is one of the main factors that cause tunnel diseases.Due to the influence of geological conditions,construction techniques and other factors,many tunnels have various voids behind the initial support lining.Based on the background of the project,this paper mainly studies the causes of cavity formation,the damage of cavities to the lining of shallow tunnels,and the prevention and control measures.The main findings of this article are as follows:(1)Through literature review and summary of on-site prevention and control experience,the reasons for the formation of voids behind the support of the tunnel under construction are analyzed in detail.It is concluded that blasting and initial support construction are direct factors that cause void formation.Hydrogeology and construction management are indirect factors that cause voids.(2)Based on the back analysis method and finite element software to establish a precise tunnel numerical model to exploring the hazards of the lining when there are voids at different positions behind the initial support of shallow tunnels,and also explore the different dimensions and double voids damage to the lining structure.Through analysis,it is concluded that: firstly,compared to other locations,the voids at the vault are more harmful to the lining;secondly,the ring size has greater impact on the lining structure than other dimensions,thirdly,the effect of the holes on the lining It is mainly manifested in the influence of large holes in the group caves on the lining structure.(3)According to the formation reasons of the voids behind the initial support and the harmful effects of the voids on the lining structure,the prevention and remediation measures for voids are proposed,which provide a certain reference for the prevention of voids behind the lining in the project.