无配筋机制砂UHPC井盖受力性能试验研究

Experimental Study on Mechanical Performance of Machine-Made Sand UHPC Manhole Cover without Reinforcement

采用机制砂替代石英砂,可制备低碳环保、成本相对低廉的UHPC.将机制砂UHPC应用于A级井盖结构中,具有高强高韧、高抗冲磨与高耐久性等特征,无需配筋工序及后期维养、施工效率高,具有良好的工程应用前景.为此,开展机制砂UHPC配合比设计与基本力学性能研究,并进行无配筋机制砂UHPC井盖模型试验、数值模拟计算与经济效益分析.结果表明,随着水胶比的增加,机制砂UHPC抗压强度和弹性模量逐渐减小,抗拉强度呈先增大后减小的趋势;当石粉含量逐渐提高时,抗压/拉强度及弹性模量呈先提高后降低的变化;随着细度模数和钢纤维掺量的增加,抗压/拉强度及弹性模量均有所提高,但提升的幅度均逐渐趋缓;未添加钢纤维时,井盖呈脆性破坏,当添加钢纤维后,由于钢纤维具有显著阻裂效应,导致井盖的结构整体刚度和延性均有所提升,表现出明显的弹塑性破坏特征;随着钢纤维掺量的增加,井盖的裂缝荷载与破坏荷载逐渐增大,但增大幅度逐渐趋缓;与传统UHPC井盖、球墨铸铁井盖、普通钢纤维混凝土井盖相比,无配筋机制砂UHPC井盖成本可节省11%~66%;无配筋机制砂UHPC井盖可采用厚度20 mm、直径400 mm~600 mm、钢纤维掺量2%的设计参数,以满足A级井盖受力需求.

Using machine-made sand instead of quartz sand,low carbon,environmental protection and relatively low cost UHPC can be prepared.The application of machine-made sand UHPC in class A manhole cover structure has the characteristics of high strength,high toughness,high abrasion resistance and high durability,and it is free of reinforcement process,high construction efficiency and late maintenance free,which has good engineering application prospect.In this paper,the proportion design and basic mechanical properties of machined sand UHPC are studied,and the model test,numerical simulation calculation and economic benefit analysis of machined sand UHPC manhole cover without reinforcement are carried out.The results show that with the increase of water-binder ratio,the compressive strength and elastic modulus of UHPC decreases gradually,and the tensile strength increases first and then decreases.When the content of stone powder increases gradually,the compressive/tensile strength and elastic modulus increase first and then decrease.With the increase of fineness modulus and steel fiber content,the compressive/tensile strength and elastic modulus are improved,but the increase amplitude is gradually slow.When steel fiber is not added,the manhole cover exhibits brittle failure.When steel fiber is added,the overall stiffness and ductility of the manhole cover are increased due to the significant crack resistance effect of steel fiber,showing obvious elastic-plastic failure characteristics.With the increase of steel fiber,the crack load and failure load of manhole cover increase gradually,but the increase amplitude gradually becomes slow.Compared with traditional UHPC manhole cover,ductile iron manhole cover,ordinary steel fiber concrete manhole cover,the cost of UHPC manhole cover without reinforcement mechanism sand can be saved by 11%~66%;The design parameters of 20mm thickness,400mm~600mm diameter and 2%steel fiber content can be adopted for UHPC manhole cover without reinforcement mechanism sand to meet the force requirements of class a manhole cover.