Technical Study On Fire Damage And Test Evaluation Of Road Tunnel Lining Structure

Owning to the characteristics such as long gallery, small room, narrow road, poor ventilation, high temperature etc , once fire occurred in a road tunnel in the mountain, it can't be put out immediately and consequences will be extremely serious. High temperature of the fire can hazards the users, and it will lead to the burst and the deterioration of the mechanical function of concrete, and do the various degrees of damages to the lining structure, which will reduce the load capacity and safety of the structure. After the fire, how to assess the degree of damages of lining structure resulting from the high temperature quickly and accurately and make a plan for the repairment and reinforcement of the structure timely, and it has a practical meaning to the safety of the tunnel structure etc.Main research work of this thesis are as follows:①Adopting CN high temperature electric heating mode, test-component ablation test of highway tunnel lining structure concrete was undertaken.through experiment about the frie damages of lining materials in fire,which is constituted with lining materials in four level(C20,C25,C30,C35), temperatures in four level(300℃, 600℃, 750℃, 900℃) and time in three level(one hour,two hours,four hours), and then deeply analyzed the superficial characteristics and the deterioration of the mechanical function of concrete, and bulit the quantitative connection of detecting items with the temperature and time in fire, and obtained regression mathematical equations, and analyzd the degree and range of damages of lining structure, which can provide theoretical basis for the analyzing evaluation of the bearing capacity of the tunnel lining structure after the fire.②A computation model " generalized load-structure model"was bulit,which can be used for calculate the bearing capacity of tunnel structure in fire conditions. This model is a improved load-structure method, changing the beam elements to plane strain elements, and achieving the coupled of the fire load condition and surrounding rock conditions. the selection method of parameters is different from the load-structure method.The definition of the lining elastic module poisson ratio etc mechanical parameters of each layer of the section is realized, in lining section thickness direction. the stress of any section in thickness direction can be obtained, internal stress of the changing situation and the degree of damage can facilitately analyzed and determined in lining arbitrary section.③Based on the ablation experiment and " generalized load-structure model ", established safety assessment method for two-lane highway tunnel lining structure in fire conditions. Taking lining structure atⅤlevel in shallow surrounding rock as an example, undertook a detailed analysis the stress changes of the lining at key points of combustion, vault, arch waist, side-wall along the thickness direction after the fire cause by burning of the cars, buses, heavy trucks, tankers. the structure calculation of the thickness of the lining before and after the 5cm thiner, 10cm thiner,15cm thiner, 20cm thiner was contrasted, whose stresses increased,compared with the relatively complete structure, but the increasing rate did not exceed 35% of the original. Take the lining as the structural design, generally safety coefficient is for 2 ~ 3, even lining by thinning, the increasing rate of stress reached the original 35%, under the premise of the structural design safety factor, lining damaged will not exceed the allowable stress, although safe coefficient can be reduced, but structure is still stable. Therefore, can eliminate destroy lining structure scheme, only to take repairment and reinforcement to the damaged lining structure.④It should do the further research work at the practical application of the test evaluation method.⑤Through lining fire physical test and data analysis, numerical computation and fire examples of road tunnel, take evaluation for the safety of road tunnel lining structure system. The achievements was used for Da Baoshan tunnel of GungShao highway,fire test data in the field was analyzed and studied, then for each section of the damage level evaluation was done, obtained some the phenomenon has and conclusion with engineering guiding significance.