海底隧道衬砌混凝土高温后性能试验研究

Experimental Study on Performance of Lining Concrete for Subsea Tunnel Subjected to High Temperature

由于通风条件差,火灾是隧道最严重的灾害之一。海底隧道地处复杂海洋环境,衬砌混凝土性能与普通混凝土相比,存在明显差异。为了研究海底隧道衬砌混凝土高温燃烧后的物理力学特性,参照厦门翔安海底隧道衬砌结构混凝土配合比制作试件,标准养护后,各组试件分别在200,300,400,600,800,1 000℃高温环境下灼烧6 h,采用自然冷却与水喷淋两种冷却方式,分别进行尺寸量测、抗压强度和抗渗试验,分析高温后混凝土的热膨胀、极限压应变、横向应变、抗压强度、弹性模量及抗渗性能等。结果表明:(1)温度低于300℃,热膨胀系数随温度变化不明显;温度高于400℃,热膨胀系数随温度升高迅速上升;与自然冷却方式相比,在水喷淋冷却方式下混凝土高温后热膨胀系数更大。(2)轴向应变相等条件下,温度低于600℃时横向应变随温度升高而增大;温度高于600℃后,横向应变随着温度增高变小。(3)温度低于300℃,抗压强度随温度变化小;温度高于300℃,抗压强度随温度升高降低。自然冷却条件下混凝土抗压强度与温度呈线性关系;而水喷淋冷却条件下,二者为非线性关系。(4)混凝土的弹性模量、抗渗等级均随温度的升高而降低,相比水喷淋冷却方式,自然冷却方式对二者影响更大。

Fire is one of the most serious disasters in tunnel because of poor ventilation condition. The submarine tunnel is located in complex marine environment, the lining concrete performance of subsea tunnel is obviously different from that of ordinary concrete. Referring to the concrete mix proportion of lining structure of Xiang＇an - Xiamen subsea tunnel, the physical and mechanical characteristics of lining concrete after high temperature combustion in subsea tunnel are studied. After making specimens and standard curing, the specimens are burned for 6 h at 200, 300,400, 600, 800, 1 000 ℃ respectively. Two cooling methods （natural cooling and water spraying ） are used respectively for measuring the dimensions, testing the compressive strength and impermeability of the specimens, and the thermal expansion, ultimate compressive strain, transverse strain, compressive strength, elastic modulus and impermeability of the concrete after high temperature are analyzed. The results shows that （1） When the temperature is below 300 ℃, the thermal expansion coefficient of concrete does not change obviously with the temperature. When the temperature is higher than 400 ℃, the thermal expansion coefficient of concrete rises rapidly with the increase of temperature. Compared with the natural cooling method, the concrete with water spray cooling has higherthermal expansion coefficient after high temperature. （2） When the axial strain is equal, the transverse strain increases with the increase of temperature when the temperature is lower than 600 ℃, the transverse strain decreases with the increase of temperature when the temperature is higher than 600 ℃. （3） When the temperature is below 300 ℃, the compressive strength has little change with the temperature. When the temperature is higher than 300 ℃, the compressive strength decreases with the increase of temperature. Under natural cooling condition, the compressive strength of concrete has linear relationship with temperature. Under the condition of water spray cooling, the relationship between the two is nonlinear. （4） The elastic modulus and impermeability grades of concrete decrease with the increase of temperature. Compared with the water spray cooling method, the natural cooling mode has a greater impact on the two.