Study On The Key Technologies Of Double Side Heading Method In Multi-arch Loess Tunnel

With the economy development of our country and the deepening of project ofwestern, infrastructure construction to promote western, especially the highwaynetwork construction to the western region as the artery of promoting regionaleconomic. The loess tunnel is emerging with the highway network go into the region ofloess,as at QingHai, GanSu, ShanXi.The same time, due to the constraints of factors oftopography, geology, linear, arch tunnel still get to use in the loess region.But becauseof the loess collapsible,low strength and arch tunnel have special features of span, theloess arched tunnel has the special mechanical behavior because of the combination ofboth. At present, domestic and foreign loess arch tunnel generally use dual sidewalldrift method, the loess arch tunnel has done some research, but did not form a systemoutcomes. Therefore, to carry out the key technologies of the double side drift methodon loess multi-arch tunnel is very necessary and practical significance.This article relying on Shanxi Qingliangsi tunnel project, through numericalsimulation of elastic-plastic finite element analysis of tunnel construction, study themechanical behavior of each part of the tunnel under different conditions. The mainissues include: safety performance evaluation under the conditions of the differentexcavation length,the Surrounding rocks of different grades, different embedmentdepth, the different cell wall thickness, different span, to obtain the key technologies ofconstruction under in the corresponding conditions.Numerical simulation by finite element analysis shows that:①The displacementdeformation and stress of excavation length of4m is larger than the excavationlength of2m, these show that the excavation length increases, the arch tunnelconstruction more difficulty.②The mechanical behavior of tunneling changesignificantly at different grade Surrounding rock.③The greater buried depth， thegreater gravity stress, the greater tunnel suffered the stress.④It is little effect in thedisplacement deformation and the force at the different core wall thickness.⑤It isgreat impact on construction of the tunnel at different Span,displacement deformationof three-lane is obvious, stress increase significantly.