Study On Temperature Field Feature And Structure Characteristics Of High Altitude Localities Road Tunnel With Complex Surrounding Rock

In view of poor theory research on structure characteristics and temperature field for cold-region road tunnels with complex geological conditions, Based on the cold-region tunnel named Qingshashan in Qinghai province, located in the east of Qinghai-Tibet plateau, serving engineering are regarded as the capital objective, through in-situ test, numerical simulation which based on FEM theory and theory analysis, mechanical characteristics of cold-region road tunnels with complex geological conditions were studied systemically.1.According to the characteristics of depending engineering, The in-situ test was synthetically taken to disclosure regularity of displacement of surrounding rock and mechanical characteristics of support structure. In-situ test results show that lining in opening of the tunnel loaded by frozen-heave force. The maximum frozen-heave force is located at crossing position between sidewall and invert. So crossing position between sidewall and invert should be reinforced. Average temperature of the depending tunnel during the coldest month is -11.2℃, while according to the code for Design of road tunnel(JTG D70-2004) frozen-heave force should be considered when average temperature of the tunnel during the coldest month less than -15℃, So the conclusion of the code should be re-determined.2.Based on the cold-region tunnel named Qingshashan, a one-way and double lane tunnel with disjunctive up and down lines,14 sections were set up to observe the ground temperature with resistance method of temperature determination. The distribution characters of the ground temperature versus time and space were studied. It is found that, 1) Ground temperature field is influenced by air temperature, nature wind, geological conditions and seepage of groundwater. 2) Maximum of negative air temperature and maximum frozen depth is not at the same section.3) with increasing of depth the ground temperature increases. 4) The temperature gradient of outer tunnel is different from inner tunnel. The obtained conclusions can guide the construction and design of tunnel in cold regions.3.According to the in-situ test results of temperature, by FEM with phase change the temperature fields of tunnel with insulation and without insulation are calculated and analyzed. The thickness and length of heat insulation layer are obtained, then insulation structure layed out of the lining is taken. By coupled FEM of temperature and stress frozen-heave force was researched under 50a freeze-thaw circulate. The results of in-situ test, elasticity formula and simulation analysis were also contrasted.4.By effective FEM model, Sensitivity analysis of mechanical parameters to deformation of surrounding rock was studied. Stability of depending tunnel in a fracture was studied, Reasonable tunnel starting scheme in partial press was studied, mechanical characteristic of long pipe shed was studied, Stability of slope with anti-slide piles under tunneling was studied.5.Strength displaying factor of tunnel support was defined. According to test result of pressure of surrounding rock, by development program based on load-structure model, Long-period security and strength displaying factor of tunnel support were studied for the depending engineering. It is found that, the tunnel applied by test pressure is safety. The minimum coefficient of safety for the tunnel applied by frozen-heave force meets the specification in tested cross-section in classified VI&V surrounding rock.