Study On The Parameters Of Barrel Vault Advanced Support Of Soft Rock Double-arch Tunnels Under Unsymmetrical Pressure

The barrel vault method is widely used in complex stratum as a secondary support technique of tunnels. It is a sophisticated method of tunneling support techniques. But, the theory study on advance-support mechanism of barrel vault is little relatively. The barrel vault parameters are selected by experience.Base on vast literatures and extensive practices, the parameters of barrel vault in soft rock double-arch tunnels under unsymmetrical pressure was investigated deeply by local experimentation, theory analysis and numerical simulation. Its application was carried throughout in many works. Research findings are as follows:1,Based on the predecessors'results of barrel vault mechanism, the superior and logical loading model and mechanism was selected. On the basis of the loading model and mechanism, the parameters determination of barrel vault of double-arch tunnels under unsymmetrical pressure under complex geology was presented.2,In this paper, the important thing is the parameters analysis of the barrel vault of double-arch tunnels under unsymmetrical pressure in excavating period. This paper discussed the effect of circumferential spacing, diameter, remaining length in rock, mechanical model, excavation footage and bench length by FLAC, and analyzed the relation between these factors and the barrel vault support.3,The 3D FEM was carried out in Fuxi double-arch tunnel under unsymmetrical pressure by using program FLAC. This paper analyzed the advance-support effect of the barrel vault, the numerical results under design parameters and optimization parameters, and compared the 3D FEM numerical results with the site test results, proved the effect of the barrel vault parameters on support.