隧道衬砌混凝土的热力耦合室内试验研究

Laboratory Thermo-Mechanical Coupling Test of Tunnel Lining Concrete

为研究受火时间和粗骨料含量与隧道衬砌混凝土宏观损伤的关系,根据隧道衬砌实际受火特点,自主改良设计一套衬砌混凝土热力耦合试验装置,研究粗骨料含量为20%、30%和40%的混凝土试块在载荷比恒为28%且不同受火时间下的损伤规律.研究结果表明:无火灾发生时,衬砌混凝土受较小荷载作用下,表面无劣化现象,质量无明显变化,残余抗压强度增加;热力耦合作用下,随着火灾时间增加,受火0.5 h后,试块表面有少许微裂纹形成,1.0 h后表面出现较宽的裂缝,细小裂缝分布较多且部分裂缝相互交叉,受火达到2.0 h,试块底面损伤严重,可以看出火灾的发展时间和程度对衬砌结构的损伤至关重要;随着混凝土粗骨料含量的降低,混凝土内部温度传导速度减慢,相同位置处的温度值变小,其表观损伤显著增加,20%粗骨料含量下质量损失率可达8.14%,而40%粗骨料含量混凝土质量损失率仅为4.10%,强度相同时,高含量粗骨料混凝土的抗火性能更优.

In order to study the relationship among the fire exposure time,the content of coarse aggregate,and the macroscopic damage of tunnel lining concrete,a thermo-mechanical coupling test device of lining concrete was independently improved according to the actual fire exposure characteristics of tunnel lining,and the damage law of concrete test blocks with 20%,30%,and 40%coarse aggregate was studied under the load ratio constant of 28%and different fire exposure time.The results show that when there is no fire accident,no deterioration appears on the surface of the lining concrete under a small load,and the quality does not change greatly.The residual compressive strength increases.Under the action of thermo-mechanical coupling,as the fire continues,a few micro-cracks form on the surface of the test block after 0.5 h of fire exposure,and wide cracks appear on the surface after 1.0 h of fire exposure,with many small cracks distributed and some cracks crossing each other.After 2.0 h of fire exposure,the bottom surface of the test block is seriously damaged.The time and degree of fire development are crucial to the damage to the lining structure.As the content of coarse aggregate of concrete decreases,the internal temperature conduction velocity of concrete slows down;the temperature value at the same position becomes smaller,and the apparent damage increases significantly.The mass loss rate of concrete with 20%coarse aggregate can reach 8.14%,while that of concrete with 40%coarse aggregate is only 4.10%,which indicates that when the strength is the same,concrete with high-content coarse aggregate has better fire resistance.