Study On Construction Mechanical Behavior Of Twin-bore Tunnel

Based on the 20 twin-bore tunnels along Phase II, Jin (Hua)-Li (Shui)-Wen (Zhou) Expressway Project, Zhejiang Province, Such three research means as laboratory model test, FEM and in-situ test are applied to comprehensively and systematically study construction mechanical behaviors of 4-lane twin-bore highway tunnel with about 25m width.Research Methods and Contents:1. Taking geometric similarity ratio C_L =20and bulk density similarity ratio C_r =1 as basic similarity ratio and grouping according to class of surrounding rock, so as to achieve complete similarity of various controlled physical and mechanical parameters in the elastic range and strictly simulate the characteristics of surrounding rock, physical property, original earth stress field, stiffness of support structures and support time, excavation process. 9 groups of similar model tests of whole construction process are completed for Class II, III and IV surrounding rock with such three construction methods as three-pilots, middle-pilot-and-half-section and middle-pilot-and-full-section, 7 groups of which are similar model tests for safety of structure system after completion of construction. Finally, 7 groups of similar model tests are completed for long-term safety of secondary linings with different reinforcement ratio for Class II, III, and IV surrounding rock.2. Adopting FEM to carry out 2D numerical simulation analysis on whole construction process and long-term safety of twin-bore tunnel body section, completing 16 groups of elasto-plastic numerical simulation analysis on the whole construction process of equal-pressure twin-bore tunnel with 0.5D, 1.0D, 1.5D and 1.8D (D is width of tunnel) buried depth 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, and completing 37 groups of elasto-plastic numerical simulation analysis on whole construction process of side-pressure twin-bore tunnel with three side-pressure ratios of 1.2, 1.4 and 1.6 and three side-pressure grades of 1:1.2 , 1:1.8 and 1:2.4 in Class II, III, IV surrounding rock, and completing 12 groups of elastic numerical simulation analysis on long-term safety of equal-pressure twin-bore tunnel with four equivalent earth-column loads of 0.75 D , 1.0D, 1.5D,2.0D in Class II,...