Analysis On The Effect Of Tunnel Excavation And Support

Since the 1990s, with the rapid development of tunnel engineering in our country ,many problems appear in the tunnel's construction. These make us suspect whether the support system consist of shotcrete ,blot and the secondary lining can guarntee the construction security and structure stability. This problem has great importance for the social and economic benefits . In view of this, taking the DaYaoshan II tunnel as the engineering background ,this paper mainly discusses the support effect and ground deformation. The study work is summarized as follows:(1) The support effect is analyzed for the stress,displacement,plastic zone distrubution and force characteristics of support structure. The result shows that the effect of shotcrete and secondary lining is better ; the bolt plays a certain role, but it has little function to structure stability. At last ,the paper makes a suggestion for canceling blot. This measure can not only reduce the costs for engineering,but also shorten construction period.(2) Ground deformation is analyzed in details under the condition of early support and second lining. Research-emphases are the strata settlement with excavation step at arch crown and haunch,the displacements of edges of tunnel.(3)Surrounding rock loosing-circle theory is used to analyze and calculate the radius of plastic zone .At the same time,a constrast analysis is performed among the radius of plastic zone calculated by Fenner formula ,the mathematrical result and the calculateing radius based on collapse height.(4)According to site monitoring data, the deformations of the surrounding rock are analyzed in detail.In addition to , the numerical simulation results are made compared with the analysis results of in-situ testing data.Research result has important guide functions to the design and construction of runnel obviously, and it can also be referred in the design, construction and research of similar tunnel in future.