Study On Fire-resistance Of The Joint Of Immersed Tunnel

As a new underwater tunnel form developed from twentieth century,immersed tunnel has its unique advantages comparing with other forms.In recent years,immersed tunnel is developing rapidly.The number of immersed tunnels worldwide is increasing year by year,while the scale is also growing.However,there are also many hidden dangers behind the rapid development.Once it breaks out of the fire in immersed tunnel,the temperature inside would rise rapidly because of the narrow space,and the smoke would fill the whole pipe at short notice.What's worse,escape route is single.In addition,temperature inside the immersed tunnel can generally get more than 1000?C,which would cause serious damage to the tunnel.Worse,the seawater outside might rush into the pipe,which makes the tunnel not be restored.Therefore,it has the extremely realistic significance to study the mechanical and thermal behavior of tunnel structure under fire.The conclusion get from the study can be the reference of fire scheme in the future,that would ensure the safety of structures under fire.According to the Hong Kong-Zhuhai-Macao Bridge Immersed Tunnel,this paper selects the weakness,the joint of immersed tunnel,as the object to research.The work is following:(1)Based on the comprehensive analysis of various cases,sum up factors such as maximum temperature,heating rate and duration,and the result was used for the fire scheme.(2)Manufacture two local full-scale components of pipe joint and segment joint,respectively put the components into the furnace to test,and observe their response under fire.Collect the temperature of each point inside the components and analyze it,this would show us the damage the components suffer.(3)Use finite element analysis software ABAQUS to simulate the reaction of components under fire without considering the influence of burst.Compare the result with the experimental data,regard the burst as a variable and get the influence it brings to internal heating of construct.(4)Summary the results of experiment and finite element analysis,give a couple of suggestions to the fire scheme in practical engineering.The study suggests that:(1)The waterstop in pipe joint was not damaged,which means that the tightness of the pipe joint can still meet the requirement after 4h of burning.The OMEGA waterstop in the segment joint was destroyed by fire in the beginning,but concrete was still well sealed.So the high temperature with 4 hour's combustion can't lead to the percolation,but the joint can't bear the high temperature any more.(2)Comparing with the joints,the main body was less destroyed and the maximum temperature was lower.Besides,contrast pipe joint with segment joint can we find that the segment joint suffers lighter damage.Therefore it's necessary to increase the protection of joints in practical engineering,especially the pipe joints.(3)Contrasting experimental data with results of numerical simulation,a conclusion can be known that the rise of temperature inside the joints would slow down if the burst doesn't exist.So the burst is one of key factors for the damage of immersed tunnel under fire.Even thought the burst can't avoid,it's still available to reduce it by various measures.