Study On The Construction Technology And Structural Stress State During The Reconstruction And Extension Process Of Loess Highway Tunnel

In recent years, with the rapid development of the economic in our country, the highwaytraffic is increasing gradually. Some early constructed tunnels already cannot satisfy thegrowing needs of the traffic flow, unable to guarantee the driving safety and meet therequirements of operation.The reconstruction and extension of this kind of tunnels, which cannot meet the demand of the traffic, is gradually put on the agenda, so as to improve thecapability of traffic and service level. But the reconstruction and extension project for loesshighway tunnel has been launched so less both at home and aboard that the theory system andgeneral construction technology is not particularly adult.Based on the reconstruction background of PengTougou tunnel (helu no.2tunnel) inShanxi province, and combined with the data collection, theoretical analysis, numericalsimulations and site monitoring, this paper simulated the comparative excavation methods ofthis tunnel and its dynamic construction process, carried on a set of key constructiontechnology which applied to the highway reconstruction projects in loess area. The mainresearch contents and conclusions are as follows:1. According to the expansion principles of highway tunnel and the actual condition ofPengTougou tunnel (helu no.2tunnel), we get the conclusion that this tunnel should adoptdouble side expansion form to extent, and prove bench method is more reasonable than fullsection method, because bench method can better use the constraint of the existing lining soas to control the deformation and reduce the stress applied on the support structure.2. Through the three dimensional numerical simulation, we obtain the change rule of thevault crown settlement, clearance convergence and stress characteristics of surrounding rockand supporting structure during the expanding process. We can also obtain the impactcoverage to the remaining part and expanded part of the tunnel as the reconstruction of theexisting tunnel.The conclusions already guided the successful construction of PengTougoutunnel (helu no.2tunnel).3. Through the site monitoring and tracking observation, we learned the change law ofeach test project during the process of tunnel reconstruction. The result can not only directlyguide the design and construction of PengTougou tunnel (helu no.2tunnel) but also comparewith the numerical simulation results.4. Through the investigations collected before the design, and the observations of theexposed surrounding rock, and combined with the results of the site monitoring, we dividedthe whole tunnel into normal construction part, small collapse part and large collapse part, andput forward the key construction technology in normal construction part and the auxiliaryconstruction measures in collapse part.