Numerical Simulation Study On Distribution Of Temperature Field And Frost Force Of Lining For Tunnel In High Altitude And Severe Cold Region

With the implementing nation policy of West-Exploitation, traffic basal constructions are developing rapidly. Highway tunnels appear a great deal, and are gradually reaching to more complicated and worse zone. For tunnels in high altitude and severe cold region, problem of freeze injure is a great puzzle and needs to be solved urgently.This thesis relied on west traffic construction scientific subject 'Research on design and construction technology of tunnels in high altitude region and complicated geological conditions', mainly used FEM numerical simulation, compared with local test and theoretical analysis, aimed at surround-rock conditions in high altitude and severe cold, studied on the change rule of temperature field and value of frost force in homogeneous and jointed surround-rock. The above research would provide theoretical base for support principle and structure design of tunnel in high altitude and severe cold region.Frost force is mainly formed by the swelling of water in rock surrounding lining when which is frozen. FEM formula analysis showed that: frost force increased along with the accretion of the porosity of rock, the expansibility of water, the rigidity of rock itself. The real stress of lining was made up of frost force and original stress caused by gravity.In jointed surround-rock, when frost force formed, part of which acted on tunnel lining directly, the other part acted on lining indirectly by rock. Homogeneous rock was a poly-phase mediator, in such surrounding-rock, the effect of frost force directly formed by water freezing was little, and frost force we concerned with was that formed by the freezing of soil in a range of surrounding tunnel lining. In FEM numerical simulation, the method that was coupling fields of thermal-structure and transient analysis was chosen. The result showed that the distributing of rock temperature field and development of corresponding frost force were related to the follow matters: depth of tunnel burial;scope of frozen rock surrounding tunnel;and crack's width, gap, distributing angel in jointed surround-rock;soil's frozen-heave ratio in homogeneous rock. In cold region, the rule of plastic collapse by frozen force of tunnel in frozen rock was different from that in frozen soil. The change of liningstress in the effect of frozen force was obvious, structure anti-measures should be adopted against such change rules. Through further research on the effect of the angel of structure plane of crack to the value and distributing rule of frost force, a method named frozen-heave vector analysis in jointed surround-rock was introduced, and corresponding formula had been built.Prevention for freeze injure of tunnel in high altitude and severe cold region should be done from many ways. Measurements should be thought of from the aspect of structure design and improvement of surrounding rock to avoid the adverse effect of freeze-thaw to tunnel structure. The change of frost force was obvious just in a certain dimension. It was a worthy advocated method to determine effective scope of freeze-thaw through FEM calculation, then design grouted ring in such a scope.Lots of aspects for tunnels in high altitude and severe cold region are requiring further study.