Abstract: The commercially available composite foaming agent, 42.5# ordinary portland cement, sand of 80 mesh, grade-I flyash, and 15 mm polyvinyl alcohol fiber were selected. The basal mix ratio was obtained, which was mcement∶mflyash∶msand=1∶0.250∶0.375, and the water-binder ratio W was 0.35, the flyash-binder ratio F was 20%, the sand-binder ratio S was 0.3, the mass addition ratio of polyvinyl alcohol fiber f was 0.10%, the volume addition ratio of foam N was 2.0. Using the controlled single variable method, 12 sets of porous lightweight concrete specimens were prepared for comparative analysis by adjusting W = 0.40, 0.45, 0.50, 0.55, F = 15%, 10%, 5%, 0%, N = 1.5, 1.0, 0.5, and 0, respectively. The stage characteristics of the stress-strain curve and the variation law of mechanical parameters of porous lightweight concrete with different mix proportions were analyzed by uniaxial compression test. The response sensitivity law of peak strength σpeak and elastic modulus E of porous lightweight concrete under W-N, N-F, and W-F interaction effects was analyzed by multi-factor interaction response models. The results show that under uniaxial compression loading, the residual strength σre of porous lightweight concrete is about 70% of σpeak, showing the characteristic of “yield pressure and absorb energy”, and the significance of this characteristic increases with the increase of N. Under multi-factor interaction effects, the morphology of the response surface for peak strength σpeak and elastic modulus E is nearly same. The proportion of medium pores in porous lightweight concrete is about 18.37%, which is the largest. The “honeycomb-shape” pore structure can effectively transfer and disperse external loads. With the characteristic of “yield pressure and absorb energy”, the damage process of the microscopic pore structure of porous lightweight concrete includes two stages: distributed damage and local damage.

Key words: tunnel engineering; porous lightweight concrete; yield pressure and absorb energy; microscopic damage

摘要： 选择市售复合发泡剂、P.O 42.5水泥、80目细砂、Ⅰ级粉煤灰及15 mm短丝聚乙烯醇纤维，得到基准配合比m水泥∶m粉煤灰∶m细砂=1∶0.250∶0.375，水胶比W=m水/(m水泥 + m粉煤灰)=0.35，粉胶比F=m粉煤灰/(m水泥 + m粉煤灰)×100%=20%，砂胶比S=m细砂 /(m水泥 + m粉煤灰)=0.3，聚乙烯醇纤维掺入百分比f=m纤维/(m水泥 + m粉煤灰 + m细砂) ×100%=0.1%，泡沫掺入体积比N=V新鲜泡沫∶V水泥砂浆=2.0；采用控制单一变量法，通过调整W=0.40、0.45、0.50、0.55，F=15%、10%、5%、0%，N=1.5、1.0、0.5、0，分别制备了12组多孔轻质混凝土试样进行单轴压缩试验，分析了不同配合比多孔轻质混凝土应力-应变曲线阶段性特征与力学参数变化规律；通过多因素交互效应响应模型分析了W-N、N-F、W-F交互效应下多孔轻质混凝土峰值强度σpeak、弹性模量E的响应敏感性规律。结果表明：单轴压缩加载下，多孔轻质混凝土的残余强度σre约为σpeak的70%，表现出“让压吸能”特征，该特征的显著性随着N的增大而增大；多因素交互效应下，多孔轻质混凝土σpeak与E的响应曲面形态基本相同；多孔轻质混凝土内部中型孔隙占比最大，约18.37%；“蜂窝状”孔隙结构可有效传递并分散外部荷载；伴随“让压吸能”特征，多孔轻质混凝土细观孔隙结构的损伤过程包含分布损伤与局部破坏2个阶段。

关键词: 隧道工程；多孔轻质混凝土；让压吸能；细观损伤