Study On In-site Test And Numerical Simulation For Twin-bore Tunnel Of Jin-Li-Wen Expressway

The study has been carried out on the bases of 20 twin-bore arching tunnels along Jin (Hua)-Li (Shui)-Wen (Zhou) Expressway, Phase II, Zhejiang Province, two research means such as FEM and in-situ test are adopted to get the comprehensive and systematical study results on the mechanical behaviors during the construction period of 4-lane twin-bore arching highway tunnel with about 25m width.Research Methods and Contents:1,Using FEM to carry out 2D numerical simulation analysis on whole construction process, completing 16 groups of elasto-plastic numerical simulation analysis on the whole construction process of equal-pressure twin-bore arching tunnel with 0.5D, LOD, 1.5D and 1.8D (D is the span of tunnel) embedded depths in the Class II, III, IV surrounding rock with such three construction methods as three-pilots, middle-pilot-and-half-section and middle-pilot-and-full-section.2,Carrying out in-situ tests in such three typical twin-bore arching tunnel as No.1 and No.2 tunnel in Shuanggangkou and Lidong tunnel. Reliable testing means are applied to compressively and systematically measure and analyze loosening range due to every stage excavation and actual stressed state of primary support and secondary linings for 12 measured cross-sections (6 cross-sections respectively for preliminary support and secondary lining).Main Research Findings:1,Putting forward safe and economical construction method for twin-bore arching tunnel with single surrounding rock condition: the construction method of three-pilots with fore-support and reserving core ground should be used in Class II and low-classification surrounding rock;The middle-pilot-and-half-section method should be used in the ground with a Class IV surrounding rock, while the middle-pilot-and-full-section. method should be used in Class IV and upper-classification surrounding rock.2,Putting forward construction method for twin-bore arching tunnel comprising multiplicate surrounding rock: middle-pilot-and-half-section is adopted in III surrounding rock. middle-pilot-and-full-section. is adopted,when surrounding rock turn to IV surrounding rock. three-pilots is adopted,when surrounding rock turn to II surrounding rock.3,Putting forward that system rockbolt and shotcrete shall be mainly adopted for preliminary support system of twin-bore arching tunnel and steel support shall be also used in Class III and low-classification surrounding rock; and rational parameter for safe and economical primary support system of 4-lane twin-bore arching tunnel with about 2D(D is the span of tunnel) depth under various surrounding rocks conditions;...