Anti-corrosion and deterioration performance of ECC-RC composite structure for shield tunnel segment under chloride attack
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摘要: 为提升盾构隧道结构在地下氯盐环境中的服役性能，利用高韧性水泥基复合材料(ECC)的优异抗裂性能，提出了1种具有ECC-钢筋混凝土(RC)叠合构造的管片结构；考虑隧道结构服役环境的单侧氯离子侵蚀与围岩持载耦合作用特征，设计了持载-加速锈蚀试验装置及模拟管片受力状态的偏压试件；对ECC-RC叠合及普通RC管片构件进行了电化学锈蚀试验以及锈蚀劣化后力学性能测试；研究了不同持载水平下2种管片构件的锈蚀劣化规律和钢筋不均匀锈蚀特性，揭示了ECC外层对管片抗锈蚀劣化性能的提升机制。试验结果表明：由于ECC层致密结构和微裂缝开展特性，相同通电电流下ECC-RC试件通电电压约为普通RC试件的6.8~7.2倍，且钢筋锈蚀率显著低于普通RC试件，表明ECC-RC叠合构造的盾构隧道结构抗锈蚀能力显著提高；锈蚀劣化后ECC-RC试件承载能力高于相同持载水平的RC试件，但极限挠度普遍偏小；持载等级对管片构件的锈蚀劣化形态及承载性能有显著影响，劣化后极限承载力与锈蚀阶段持载水平呈负相关，持载相较无劣化极限承载力每增加1/10，RC管片的极限承载力将下降约2.6%，而ECC-RC叠合管片的极限承载力将下降约4.2%；持载下普通RC试件钢筋沿纵向产生显著不均匀锈蚀，持载裂缝位置的钢筋易出现坑蚀，且持载水平越大，不均匀特征越明显；由于ECC层在持载下多微裂缝的开裂模式，ECC-RC试件内部钢筋锈蚀分布也相对均匀。Abstract: To boost the service performance of shield tunnel structure in an underground chloride environment, the engineered cementitious composite (ECC) with excellent cracking resistance were utilized to form an ECC-reinforced concrete (RC) composite structure for segments. The characteristics of single-sided chloride ion attack and sustained-loading coupling of the surrounding rock in the service environment of the tunnel were taken into consideration. A sustained-loading-accelerated corrosion testing apparatus and the eccentrically compressed specimens simulating the working state of the tunnel segment were designed. Electrochemical corrosion experiments and the tests of mechanical properties after corrosion deterioration were conducted on ECC-RC composite and conventional RC segment specimens. The corrosion deterioration rule and uneven corrosion characteristic of the steel bars of the two specimens were investigated at different sustained-loading levels. The mechanism of enhancing anti-corrosion deterioration performance with the ECC external layer was then revealed. Experimental results show that due to the dense structure and micro-cracking properties of the ECC layer, ECC-RC specimens are 6.8-7.2 times higher than conventional RC specimens in the applied voltage under the same current. The steel bar corrosion ratio of ECC-RC specimens is significantly lower than that of conventional RC specimens. It indicates that the shield tunnel segment with ECC-RC composite structure sees a significant increase in the anti-corrosion performance. Deteriorated ECC-RC specimens have higher loading capacity but smaller ultimate deflection than their RC counterparts with the same sustained-loading level. The sustained-loading level highly influences the corrosion deterioration patterns and bearing capacities of specimens. The ultimate bearing capacity of the deteriorated specimens is negatively correlated with the sustained-loading level at the corrosion stage. Compared with the ultimate bearing capacity of the non-deterioration specimens, when the loading capacity increases 1/10, the ultimate bearing capacity of RC tunnel segments drops by 2.6%, while that of ECC-RC composite tunnel segments decreases by 4.2%. The sustained-load steel bar in RC specimens presents significant uneven longitudinal corrosion. Pitting corrosion tends to occur at the location of cracks with sustained loading. The uneven corrosion becomes severer with the higher sustained-loading level. Due to the multiple micro-cracking mode of the ECC layer under sustained loading, the steel bar in ECC-RC specimens shows relatively uniform corrosion.
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图 1 模拟管片服役状态的试件设计
Figure 1. Specimen design to simulate service state of tunnel segment
图 9 普通RC试件锈蚀劣化形态(侧面)
Figure 9. Corrosion deterioration patterns of conventional RC specimens (side view)
图 10 普通RC试件锈蚀劣化形态(顶面)
Figure 10. Corrosion deterioration patterns of conventional RC specimens (top view)
图 11 ECC-RC试件锈蚀劣化形态(侧面)
Figure 11. Corrosion deterioration patterns of ECC-RC specimens (side view)
图 12 ECC-RC试件锈蚀劣化形态(顶面)
Figure 12. Corrosion deterioration patterns of ECC-RC specimens (top view)
图 17 加载过程中典型试件钢筋应变分布
Figure 17. Strain distributions of steel bars in typical specimens during loading process
图 20 极限荷载随锈蚀阶段持载关系
Figure 20. Relationship between ultimate load and sustained load at corrosion stage
图 22 R-0-C锈蚀钢筋残余面积及对应的表面形貌
Figure 22. Residual areas and corresponding surface morphologies of R-0-C corroded steel bar
图 23 无持载试件钢筋残余面积与锈蚀形态
Figure 23. Residual areas and corrosion patterns of steel bar in specimens without sustained loading
图 24 持载试件钢筋残余面积与拉伸应变分布
Figure 24. Residual areas and tensile strain distributions of steel bar in specimens with sustained loading
图 25 不均匀系数随持载变化关系
Figure 25. Relationship between uneven coefficients and sustained loading
图 26 锈蚀钢筋残余面积分布直方图及拟合概率分布曲线
Figure 26. Histograms of residual area distribution of corroded steel bar and fitting probability distribution curves
图 27 氯盐侵蚀环境中开裂隧道管片服役状态
Figure 27. Service state of cracked tunnel segments in chloride attack environment
表 1 基体材料配合比
Table 1. Proportions of matrix materials
kg·m-3 ECC 水泥 矿粉 石灰石粉 硅灰 石英砂 PE纤维 减水剂 水 528 566 74 111 446 20 3 388 C50 水泥 粗骨料 细骨料 水 575 957 612 230 
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表 2 基体材料抗压强度
Table 2. Compressive strengths of matrix materials
MPa 材料 28 d抗压强度 平均值 标准差 试件1 试件2 试件3 C50 50.0 48.2 51.2 49.8 1.2 ECC 51.2 50.0 40.0 47.1 5.0
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表 3 试件设计
Table 3. Specimen design
持载+锈蚀情况 对应工况 普通RC试件 ECC-RC试件 120 kN+锈蚀 正常服役 R-120-C E-120-C 180 kN+锈蚀 超载服役 R-180-C E-180-C 240 kN+锈蚀 严重超载服役 R-240-C E-240-C 无持载+锈蚀 无持载 R-0-C E-0-C 无持载+无锈蚀 对照 R-0-N E-0-N
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表 4 纵向锈胀裂缝宽度统计
Table 4. Statistics for widths of longitudinal corrosive expanding cracks
mm 试件 第10天最大裂缝宽度 第30天最大裂缝宽度 R-0-C 0.41 0.78 R-120-C 0.53 0.63 R-180-C 0.42 0.58 R-240-C 0.32 0.42
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表 5 实测极限承载力与挠度
Table 5. Actual measured ultimate bearing capacities and deflections
试件 极限承载力/kN 极限挠度/ mm 试件 极限承载力/kN 极限挠度/ mm R-0-N 484.2 5.00 E-0-N 544.9 2.62 R-0-C 458.5 3.31 E-0-C 525.7 2.64 R-120-C 427.9 4.08 E-120-C 492.9 2.75 R-180-C 414.9 4.65 E-180-C 460.8 4.06 R-240-C 393.1 7.13 E-240-C 420.6 3.82
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表 6 锈蚀率统计
Table 6. Statistics of corrosion rate
试件 质量锈蚀率 锈蚀效率 试件 质量锈蚀率 锈蚀效率 R-0-C 0.097 0.81 E-0-C 0.063 0.52 R-120-C 0.110 0.92 E-120-C 0.086 0.69 R-180-C 0.108 0.90 E-180-C 0.073 0.61 R-240-C 0.108 0.90 E-240-C 0.095 0.79
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表 7 各试件钢筋锈蚀情况统计表
Table 7. Statistics for corrosion of steel bar in each specimen
mm2 横截面积 未锈蚀 R-0-C E-0-C R-120-C E-120-C R-180-C E-180-C R-240-C E-240-C savg 247.24 224.74 231.67 221.17 228.19 223.07 229.98 219.95 224.50 smax 252.88 251.62 247.33 237.32 243.94 246.91 253.07 249.14 240.67 smin 242.44 206.53 213.29 201.08 210.35 192.12 206.81 138.42 200.73
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表 8 锈蚀钢筋残余面积概率分布拟合曲线参数
Table 8. Parameters of fitting curves for probability distribution of residual area of corroded steel bar
试件 kj x1 wj K-S统计量 R-120-C 1.000 221.180 6.317 0.096 0.528 0.472 217.780 224.970 6.538 3.074 0.025 R-180-C 1.000 220.070 11.382 0.048 0.879 0.121 220.750 239.930 10.109 2.119 0.030 R-240-C 1.000 220.590 19.188 0.124 0.435 0.565 207.060 230.990 21.039 7.876 0.047 R-0-C 1.000 224.740 6.740 0.074 0.851 0.149 222.820 235.670 4.951 4.951 0.020 E-120-C 1.000 228.190 6.670 0.042 0.333 0.667 222.270 231.160 5.192 5.192 0.030 E-180-C 1.000 229.980 7.941 0.054 0.465 0.535 228.250 231.490 9.173 6.314 0.047 E-240-C 1.000 224.500 6.542 0.034 0.095 0.905 213.450 225.660 5.475 5.475 0.031 E-0-C 1.000 231.670 8.201 0.069 0.421 0.579 223.640 237.500 4.524 4.524 0.025
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