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隧道初期支护喷射混凝土目前存在干喷、湿喷两种基本工艺,干喷混凝土由于难以准确控制水灰比和速凝剂掺量,故平均强度较低,且离散性大;湿喷工艺可以通过对混凝土配合比(特别是水灰比)和速凝剂掺量的有效控制来确保喷射混凝土强度及减小强度变异系数。以承朝高速公路长逢沟隧道为工程实例,从湿喷混凝土配合比设计及优化、机械选择组合、施工工艺、工作参数、质量控制等方面进行了系统的论述、总结,对湿喷混凝土强度数据和回弹率进行了详细的统计分析;实践证明,湿喷工艺对初期支护喷射混凝土强度能进行有效的控制和保证,减少回弹量等方面效果明显;湿喷混凝土配合比强度设计及工作性优化、工作参数及液体速凝剂选择是质量控制的关键,对隧道初期支护喷射混凝土施工有一定的指导意义。
At present, there are two kinds of basic technologies of dry shotcrete and wet shotcrete in shotcrete of initial support in tunnel. Because of the difficulty in accurately controlling the ratio of water-cement and quick-setting admixture, dry shotcrete has low average strength and large discreteness. Through the effective control of concrete mix ratio (especially water-cement ratio) and quick-setting admixture dosage to ensure the strength of shotcrete and reduce the strength variation coefficient. Taking Changfenggou Tunnel of Chengchao Expressway as an example, the paper systematically discusses and summarizes the design and optimization of mix ratio of wet shotcrete, mechanical selection, construction technology, working parameters and quality control, Data and rebound rate carried out a detailed statistical analysis; practice has proved that the wet spray process on the initial support shotcrete strength can be effectively controlled and guaranteed, reducing the amount of rebound and other aspects of the effect is obvious; wet shotcrete mix design strength and Working optimization, working parameters and the selection of liquid quick-setting agent are the key points of quality control, which is of guiding significance to the initial support and shotcrete construction of tunnel.