湿喷混凝土回弹率影响因素的研究进展

为了理清湿喷混凝土回弹率的主要控制因素,提高喷射支护技术的经济性,从混凝土原材料、配合比、施工工艺三个方面综述了各因素对回弹率的影响。从原材料角度,掺加掺合料、掺加纤维、提高掺合料细度、降低骨料最大粒径等措施均可降低混凝土在喷射传输过程中的分散性,降低回弹率;从配合比角度,增加胶凝材料用量、提高混凝土稠度、调整适宜的坍落度和凝结时间等措施均可提高喷射混凝土的粘附效率,降低回弹率;从施工工艺角度,适当提高一次喷射厚度、取直角作为喷射角、控制合理的工作风压等措施均可显著降低回弹率。目前研究多针对单一因素进行考察,忽略了各因素对回弹率的耦合作用。今后应进一步加强耦合作用相关理论研究,建立各因素间的内在联系,强化动态调控机制。

Advance of study on factors of influences on rebound rate of wet shotcrete

In order to sort out the main dominant factors of the rebound rate of wet shotcrete and improve the economy of shotcreting supporting technique， the influences of all the relevant factors on the rebound rate are reviewed in three aspects， i.e. raw materials， mixture proportions， construction technology of the concrete. So far as the raw materials are concerned， the dispersity of the concrete during its shot transmission process can be lowered， while its rebound rate can be decrease as well by means of adding admixtures and fibres， increasing the finenesses of admixtures and decreasing the maximum particle size of the aggregate. From the view point of the mixture proportions， the adhesive efficiency of the shotcrete can be enhanced， while its rebound rate can be decrease as well by means of increasing the proportion of cementing material， enhancing the concrete consistence and setting up appropriate slump and setting time. From the aspect of construction technology， the rebound rate can be significantly decreased by means of appropriately increasing the build up shotcreting thickness， taking right angle as the shotcreting angle and controlling the reasonable working air pressure. At present， most of the relevant studies are made on a single factor， thus the coupling effects among all the factors concerned are neglected. Therefore， the study on the relevant theory of the coupling effect must be strengthened for establishing the internal relationships among all the factors and intensifying the dynamic regulation mechanism concerned in the days to come.