Research On The Cave Body Excavation Method And Foundation Treatment Technique Of Loess Tunnel

Hanguguan tunnel is a southward moving project of national highway G310,Lingbao city,SanMenXia,it is located in the collapsible loess area,with a long line and a larger undulating terrain,the maximum buried depth of the tunnel is 107m,and the shallowest buried depth of the tunnel is 18m.The collapsible loess has the obvious regional characteristics.The analysis of the causes,characteristics and deformation mechanism of the collapsible loess in the area through which the Hanguguan tunnel passes is of great significance to optimize the excavation method of the tunnel,screen the treatment technology of the weaken loess collapsibility,and ensure the safety and stability of the surrounding rock and support structure in the construction processIn this paper,based on the Hanguguan loess tunnel,SanMenXia as the research object,by combining with the project example of super large section loess highway tunnel construction in our country and the analysis for the force conditions of the collapsible loess highway tunnel structure and the surrounding rock in the construction process by the field monitoring and measuring data,the conversion of the excavation and supporting method in the collapsible loess tunnel construction and the treatment technique of collapsible foundation are studied.The main research contents and conclusions of this paper are as follows(1)the causes,characteristics and deformation reasons of loess are summarized and analyzed,and the excavation and support methods of loess tunnel are summarized,compared,and analyzed in the aspects of the surrounding rock settlement,construction period,construction difficulty and cost,and so on(2)In the process of tunnel excavation,this paper puts forward to apply the construction technique methods of CRD normal three-stairs seven-steps excavation method conversion,and combines the monitoring and measuring data analysis of the field cave ceiling settlement and surrounding rock convergence displacement deformation,indicating that by use of the construction technique methods of CRD normal three-stairs seven-steps excavation method conversion in the collapsible loess tunnel,the stability and deformation of the surrounding rock structure can be effectively controlled to ensure the safety of tunnel construction(3)The vibration caused by the construction of cement soil compaction pile is measured and tested,the results have shown that there is no obvious crack produced on the surface of the initial support,the vault subsidence is 1?2mm,and the horizontal convergence is 2?3mm,the generated vibration has little influence on the safety and stability of the initial support structure of the tunnel;moreover,the results of the sample testing of the treated soil between the piles meet the design requirements of the compactness and collapsibility,indicating that the treatment of collapsible loess foundation by use of the cement soil compaction pile has a good effect.