Experiment Study On Fire Resistance Of Roof Spacer Construction In Independent Smoke Extraction Passage In Extra-long Highway Tunnel

With the social development, more and more extra-long highway tunnels appear, it is an important concern to protect tunnel structure from fire in tunnel fire safety engineering. There is no mature experience and corresponding code for centralized smoke exhaust mode in independent smoke shaft by now, which has limited the application of this technique. As there is no research on key safety parameters of independence smoke shaft both in fire and after fire, the application of this technology is limited.Based on the hot somke test of tunnel model, this papper presents the fire resistance of the reinforced concrete structure of independant smoke shaft (including both roof spacer and corbel structure) and plain concrete lining structure by model test. On the basis of fire experiments, theoretical analysis and numerical simulation, a seires of valuable findings are achieved. The main researches are as following:(1) By fire tests of roof spacer under HC standard curve, 900℃,800℃,700℃for 2 hours, the temperature field distribution and deflection varition of roof spacer under coupling of load and temperature is studied.(2) The damage characteristicsm, damage degree and damage grade of variant working conditions after fire are tested, the nonlinear relation between bearing ability of roof spacer and fire temperture is obtained, the residual bearing ability decrease by 76%,50%,25% and 24% respectively.(3) By fire test under HC standard curve for 2 hours, the temperature field distribution and high temperature reaction of corbel structure with (without) fire retardant coatings are obtained. The bearing ability after fire is tested and the declines degree is obtained,(4) The experiments of adhesive steel bar under and after fire are tested, the temperature field distribution, deformation features and deformation law under load after fire are obtained, the safety of the joint is analyzed.(5) The pull-out tests of adhesive steel bar under different temperatures and different load are studied, the ultimate bearing ability, ultimate bond stress and capacity loss under room temperature, natural cooling after high temperature and constant high temperature are analyzed, some key paremeters, such as failure temperature and slided displacement are obtained, the law of ultimate bond stress and capacity loss under and sfter high temperature is obtained.(6) On the basis of test research and theoretical analysis, by using finite element analysis, the evaluation standard and method of damage grade of full-scale roof spacer after fire are carried out, the safety of roof spacer is evaluated, and the strengthening area is proposed.This study will fill in the gap in the field of fire resistance research of extra-long highway tunnels, raise the level of disaster prevention and reduction, also, provide great reference and guiding significance for fire engineering design, code modification and practical application of engineering.