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文章阐述了混凝土喷射机的选择与应用和喷射前的准备工作;分析了喷射过程的控制与处理,包括喷射剂的应用、确定喷射厚度、控制含水率、混凝土回弹问题的控制与处理、控制水泥预水化、混凝土喷射的养护工作. 相似文献
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《江西建材》2017,(4)
喷射混凝土技术已经广泛应用于隧道、地下硐室、边坡支护等土木工程,然而现行国内规范标准对喷射混凝土的质量评定仍然采用单一的强度指标,不能全面合理地反映喷射混凝土的实际工作机理。传统的喷射混凝土强度检测法不仅费时费力,而且获得的强度值与实际喷射混凝土质量存在较大差异,已难以满足喷射混凝土质量性能评价要求。文章在综合分析评述当前喷射混凝土质量检测评价的国内外现状的基础上,提出利用气压射钉枪检测喷射混凝土强度和圆板弯曲试验检测喷射混凝土的弯曲韧性相结合来综合评价喷射混凝土的工作性能,对改进国内喷射混凝土质量性能评价体系,建立新的喷射混凝土质量测试方法和评定标准具有一定的借鉴意义。 相似文献
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对掺入钢纤维的喷射混凝土、掺入聚丙烯纤维和钢纤维的复合纤维喷射混凝土和普通素混凝土三种喷射混凝土进行快速碳化试验,建立了基于试验的碳化深度预测计算式,该计算式有碳化速度系数和初始碳化难易程度两个常数,经对比与实际吻合良好。试验结果表明:在喷射混凝土中掺入纤维可以有效改善喷射混凝土的抗碳化性能。在配合比相同及纤维掺量适宜的条件下,其抗碳化性:复合纤维喷射混凝土钢纤维喷射混凝土普通喷射混凝土。在考虑了自然环境与试验环境的主要区别的基础之上,提出了基于试验的自然环境下纤维喷射混凝土碳化深度的预测模型。由于纤维喷射混凝土实际工程测试数据缺乏,该模型尚需实际检验与修正。 相似文献
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喷射混凝土的抗渗性能与喷射混凝土的使用年限、承受水压力、喷射混凝土的龄期等因素密切相关。以喷射混凝土的渗水高度作为其抗渗性能的评价指标,通过室内试验研究了基于复合胶凝材的喷射混凝土渗水高度与加压时间、承受水压力、混凝土龄期的相关关系;并进一步研究了喷射混凝土回弹率、吸水率等,以及这些指标与抗渗性能的相关性。通过研究得到,掺加复合胶凝材对提高喷射混凝土的抗渗性能有显著作用;加压时间和水压力量值对渗水高度的影响很大,加压时间与渗水高度呈正比关系,水压力大小与渗水高度成近似正比关系;随着龄期的增加,渗水高度逐步减小,28 d龄期后渗水高度趋于稳定;单掺复合胶凝材的喷射混凝土吸水率低于掺加复合胶凝材和聚丙烯纤维的喷射混凝土,抗渗性更好一些;但是加入聚丙烯纤维后,与只掺加复合胶凝材的混凝土比较,其回弹率大大降低。 相似文献
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试验以采用喷射混凝土单层衬砌结构隧道工程为背景,对不同水胶比、粉煤灰掺量及钢纤维掺量喷射混凝土力学性能、渗透性能进行研究。结果表明
,喷射混凝土具有高早龄期强度,当养护龄期大于1d时,喷射混凝土强度小于普通混凝土且差值逐渐增大。随着水胶比增大和钢纤维掺量降低,喷射混凝土
强度及渗透性降低;随着粉煤灰掺量增大,喷射混凝土抗压强度先增大后减小,渗透性先减小后增大,劈裂抗拉强度持续增大。同时,对喷射混凝土碳化、
冻融、硫酸盐侵蚀及氯离子侵蚀耐久性能进行研究,并与同配合比普通混凝土进行对比。而后,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、热分析及压
汞测孔法(MIP)对侵蚀后喷射混凝土微观结构、侵蚀产物及孔结构进行分析,研究喷射混凝土与普通混凝土耐久性能差异及机理。结果表明:喷射混凝土碳
化、冻融及硫酸盐侵蚀耐久性能优于普通混凝土,但抗氯离子侵蚀性能较普通混凝土弱。钢纤维的加入使喷射混凝土耐久性能提高,但对抗氯离子侵蚀性能
提升不明显。 相似文献
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三峡右岸电站地下厂房采用了钢纤维喷射混凝土支护,通过对喷射混凝土层与层之间、喷射混凝土与围岩之间的粘结强度进行检验分析,验证喷射混凝土的强度指标和喷射工艺的标准化,保证施工质量,有效地控制了永久支护效果,对地下厂房的施工安全起到了至关重要的作用.通过对三峡右岸地下电站主厂房喷射混凝土粘结强度检验方法中存在的弊端进行的总结分析,对规范中的粘结强度指标提出了不同看法. 相似文献
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结合工作实践经验,重点个绍了有关高边坡挂网锚喷防护的设计要点、施工方案的各工序,阐述了有关质量管理和检测方法,以提高边坡的整体稳定性。 相似文献
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One of the commonly used stabilization systems for rock tunnels is shotcrete. This fine aggregate mortar is usually reinforced for improving its tensile and shear strength. In deep tunnels, its capacity to absorb energy has been recently considered for design purposes, as large displacements of the wall are expected. Two of the most used materials of reinforcement are steel welded-wire mesh and fibers (steel or polypropylene) in the shotcrete mix. This study presents the results and discussion of an experimental test program conducted to obtain the load-deformation curves of reinforced shotcrete, according to ASTM C 1550, using geosynthetics grids and geotextiles as alternative reinforcement materials. In addition, plain shotcrete and steel welded-wire mesh reinforced shotcrete specimens are also considered in the experimental program as benchmark cases. The experimental results are analyzed in terms of maximum strength and toughness. Results show that the use of geosynthetics as a reinforcement material is a promising alternative to obtain shotcrete with energy absorption capacity comparable with the most common reinforcement materials used. 相似文献
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通过对喷射混凝土的实际受力机制以及隧洞施工过程响应特征的研究,发现喷混凝土的施工和受力过程具有非常复杂的时间和空间效应。研究表明:喷混凝土支护结构的受力会随着隧洞掌子面的推进而越来越大;喷混凝土从初喷到复喷,直至达到设计强度,其变形和强度的力学特性是随着时间而逐渐变化的,即混凝土的起强过程;喷混凝土与围岩间接触面的力学性质也随时间发生变化;支护结构设计分析中,若不考虑喷混凝土施工和力学特性的时间和空间效应,将会高估喷混凝土的实际受力状态。通过以色列Kokhav Hayarden抽蓄电站施工支洞喷混凝土设计的实际应用,证明了隧洞喷混凝土支护设计计算中考虑其时间和空间效应是必要的,否则将会高估其实际受力。 相似文献
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Jonas Holmgren 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1987,2(3)
This study describes rock reinforcement through the use of reinforced shotcrete in structural interaction with rock bolts. The intention of the investigation was to increase the knowledge of steel-fibre-reinforced shotcrete and the way in which bolt anchorage in shotcrete is designed. The researcher performed 22 large-scale laboratory tests on bolt-anchored, reinforced shotcrete lays, 19 of which were reinforced with Bekaert steel fibres, 2 with cold-tensioned reinforcement mesh, and 1 with an annealed mesh. Fibre content, fibre length and anchorage of the bolt in the shotcrete varied in the tests. For each large-scale test, adhesion tests on the rock-shotcrete interface were performed, as well as strength on sawn-out shotcrete cubes and beams both with and without fibres. The concrete mass was tested using cast cubes. Four large-scale tests on extremely thin fibre-reinforced linings without bolt anchorage also were performed. Two specimens contained steel fibres, and two contained glass fibres. Details also are provided of shear tests on split steel-fibre-reinforced test specimens on a small scale. The paper concludes with a discussion of the test results. 相似文献
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对隧道施工中常见的三种混凝土喷射形式进行了介绍,并对湿式喷射混凝土的施工技术进行了研究,论述了喷射前的准备工作、原材料选择、配合比设计等注意事项,着重阐明了喷射混凝土的施工流程及检测要求,以提高施工效率。 相似文献
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隧道钢纤维喷射混凝土性能试验及其工程应用 总被引:5,自引:1,他引:4
根据钢纤维喷射混凝土结构力学原理,为了研究钢纤维混凝土喷层在隧道单层永久衬砌支护中适用性,先分析钢纤维在混凝土中的增强力学作用机制,然后完成钢纤维喷射混凝土合理配比、抗拉、抗压、抗折及抗折初裂强度和弯曲性能等指标的室内试验;并结合具体的隧道现场喷射试验,以及围岩应力、钢纤维混凝土喷层应力及洞周附加水平收敛等监测数据进行分析。研究结果表明,钢纤维喷混凝土抗拉、抗折强度高,韧性好,喷层中的应力分布较均匀,具有较好的让压能力,喷射作业回弹损失量减少,说明钢纤维喷射混凝土是一种理想的单层衬砌支护材料,具有较好的推广应用价值。 相似文献
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S. V. L. Barrett D. R. McCreath 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1995,10(1)
The precise mechanisms by which shotcrete acts to stabilize the ground around a tunnel are not well understood and are the focus of ongoing research and discussion. Consequently design of shotcrete support is still more of an art than a science, with the majority of designs based on past experiences in similar settings, on empirical recommendations or on monitoring and modification during construction. In an attempt to provide an analytical alternative, and to gain some insight concerning the mechanisms which control shotcrete failure in blockyground, four deterministic design models are presented which illustrate shotcrete's effectiveness at supporting structurally defined blocks and wedges, thereby avoiding progressive loosening and destabilization of the rock mass around an opening. These models may also be used to verify or refine design recommendations which have been based initially on empirical guidelines, and to give an indication of the approximate factor of safety. Examples of typical design charts are given. Results of analyses based on these models show that failure of shotcrete is generally a two-step process, governed initially by loss of adhesion to the rock, followed by flexural failure. These results indicate that while adhesion is of critical importance in maximizing the peak ground support capacity of the shotcrete, flexural strength and toughness play a critical role in the post-peak region, once adhesion is lost. 相似文献