Laboratory Thermo-Mechanical Coupling Test of Tunnel Lining Concrete
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摘要:
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.
Abstract: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.
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图 3 温度、粗骨料含量与受火面距离关系响应
Figure 3. Response relationship among temperature, coarse aggregate content, and distance of fire exposure surface
图 4 温度、受火时间与受火面距离关系响应图
Figure 4. Response relationship among temperature, fire exposure time, and distance of fire exposure surface
图 5 不同粗骨料含量混凝土受火底面
Figure 5. Bottom view of concrete with different coarse aggregate contents under fire
图 7 不同受火时间下混凝土受火底面
Figure 7. Bottom view of concrete under different fire exposure time
表 1 混凝土试块配合比
Table 1. Mix ratio of concrete test blocks
kg/m3 粗骨料
含量%水胶比 水 水泥 粉煤灰 矿粉 大碎石 小碎石 河砂 减水剂 40 0.35 147 189 105 126 733 314 775 4.20 30 0.35 228 292 163 195 563 242 606 0.40 20 0.35 318 408 227 272 375 161 404 0.16 
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表 2 试验工况
Table 2. Test conditions
试验类型 受火时间/h 有无比 粗骨料/% 试件编号 试件总数/个 静载试验 0 无 40 WS1-WS3、WS1'- WS3' 18 （WS1'−WS9'试块用于热力
耦合试验前确定强度）30 WS4-WS6、WS4'-WS6' 20 WS7-WS9、WS7'-WS9' 受火试验 0.5 有 40 WA1 5 1.0 40 WA2 2.0 40 WA3 1.0 30 WB 1.0 20 WC 静载试验 0 无 40 WA 6 0.5 无 40 WA1 1.0 无 40 WA2 2.0 无 40 WA3 1.0 有 30 WB 1.0 有 20 WC 注：1. 除用于强度标定的试块为一组外，其余试块均制作相同的2组，一组用于扫描，一组用于温度测量，编号 按WAT等形式进行，因此，试块总数为30个；2. 荷载比即为试验时所加荷载与试验前极限抗压强度之比.
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表 3 相对质量变化
Table 3. Relative mass change
试块编号 m1/g m2/g Δm/g α/% WA 2 443 2 433 10 0.41 WA1 2 450 2 373 77 3.14 WA2 2 440 2 340 100 4.10 WA3 2 448 2 333 115 4.70 WB 2 380 2 251 129 5.42 WC 2 229 2 111 118 8.14
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表 4 28 d混凝土抗压强度值
Table 4. Concrete compressive strength value after 28 d
粗骨料含量/% 抗压强度/MPa 20 57.16 30 58.01 40 61.72
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表 5 不同龄期混凝土强度值
Table 5. Concrete strength values of different ages
粗骨料含量/
%28 d 强度/
MPa90 d 强度/
MPa强度变化率/
%40 61.72 66.3 7.4 30 58.01 68.9 18.8 20 57.16 71.7 25.4
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表 6 不同粗骨料含量下的抗压强度损失率
Table 6. Compressive strength loss rate under different coarse aggregate contents
粗骨料含量/% σ0/MPa σs/MPa f/% 40 66.3 60.41 8.88 30 68.9 63.10 8.42 40 71.7 62.36 13.03
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表 7 不同受火时间下的抗压强度损失率
Table 7. Compressive strength loss rate under different fire exposure time
受火时间/h σ0/MPa σs/MPa f/% 0 66.3 70.50 −6.33 0.5 66.3 65.80 0.75 1.0 66.3 60.41 8.88 2.0 66.3 55.50 16.30
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