隧道湿喷混凝土回弹量控制要点探讨

混凝土湿喷工艺是隧道初期支护施工过程中一关键环节，能确保湿喷混凝土质量的安全可靠，同时改善了隧道施工作业环境。通过湿喷混凝土回弹量控制，更能有效缩短湿喷作业时间，达到“及时支护”的设计理念，降低隧道施工过程中的作业风险。     

初支混凝土硬化特性与围岩流变耦合作用机制

喷射混凝土作为初期支护重要组成部分广泛应用于隧道工程。深埋软岩隧道开挖时，喷射混凝土硬化特性及围岩流变效应均于时间有关，使得围岩变形及结构受力错综复杂。基于此，该文建立了考虑喷射混凝土硬化特性与围岩流变效应的耦合解析模型，阐明了流变岩体隧道“支护-围岩”动态演化机制，分析了喷射混凝土设计参数、隧道工程参数及围岩流变特性等对“支护-围岩”动态作用的影响机制，并通过具体实例探讨了不同支护类型的时效支护特性。分析表明：喷射混凝土施作初期刚度较低，在围岩流变特性及开挖空间效应下围岩变形速率大，而喷射混凝土承担荷载较不考虑其硬化特性时要小，对于流变岩体隧道宜采用早强混凝土限制围岩早期变形；围岩流变荷载与喷射混凝土刚度均随时间逐渐增大，不考虑围岩流变效应会低估喷射混凝土对围岩变形控制效果及所承担荷载水平；型钢钢架+喷混支护体系刚度较大有利于限制围岩变形，格栅钢架+喷混支护刚度较小更利于围岩应力释放；隧道支护时机的选择应综合考虑围岩流变效应、支护类型、喷混硬化特性、隧道掘进速率的影响，进一步给出了不同支护类型的支护时机-掘进速度的极限关系曲线。研究成果可为类似隧道工程支护设计、施工提供理论依据。     

喷锚支护施工技术在隧道工程中的应用研究

随着我国经济实力的提升,国家对于各项基础建设工作十分重视,交通事业也在良好的社会形势下得到了长足的发展。各个地区的交通工程数量不断增加。由于各个地区的自然环境有较大区别,公路工程的建设的过程中,部分地区需要开挖隧道,才能优化交通条件,需要运用到相关隧道施工技术,喷锚支护施工技术则是其中重要的技术之一。该项技术能够对隧道有强化固定的作用,有效的提高地层的稳定性,保障施工安全。本文简单的结合某工程的情况介绍了喷锚支护施工技术在隧道工程中的应用,包括确定喷射混凝土原料的比例、喷射混凝土原料配合比、清理开挖面围岩、喷射混凝土、设置锚杆及配套材料、覆盖混凝土等,为隧道的施工人员提供一定的参考与借鉴。     

轻骨料喷射混凝土工作性能及早期强度试验研究

轻骨料喷射混凝土是用轻骨料代替普通混凝土中粗骨料或细骨料应用于隧道的喷射混凝土中。本文采用正交试验对喷射混凝土较为关注的工作性能和早期强度进行了测试,根据实验结果,将配合比进行优化,在贵州马尾坡隧道进行现场施工,并对现场施工效果进行了钻芯取样测试。现场测试效果良好,满足实际工程需要,验证了轻骨料喷射混凝土在隧道锚喷支护中应用的可行性,为轻骨料在喷射混凝土中的应用提供理论依据。     

喷射混凝土早龄期徐变的试验研究及预测

为了掌握隧道初期支护喷射混凝土的早龄期徐变性能,以地铁和公路隧道最为常用的两种配合比的喷射混凝土为研究对象,模拟施工环境,对喷射混凝土的早龄期徐变性能进行试验研究,完成了不同龄期试件的强度、收缩和受压应变测试,分析了早龄期喷射混凝土徐变特点。将试验值与B3模型和GL2000模型预测值进行比较后,分析了造成试验值与模型预测值之间存在较大偏差的主要原因,有针对性的对GL2000模型的关键项进行了修正,提出了适合于早龄期喷射混凝土徐变度的预测模型。     

浅析降低隧道喷射混凝土回弹率的方法

本文从喷射混凝土原材、配合比、旅工工艺、喷射压力等七个方面对降低其回弹率进行较为详细的叙述，为今后隧道喷射混凝土施工提供参考。     

钢管拱初期支护在隧道施工中的应用

随着社会经济的不断发展,根据我国道路发展的需要,公路等级不断提高,穿越山岭地区的公路长大隧道也越来越多,隧道埋深大,设计地质勘测难度大大提升,地质勘测不全面导致隧道支护设计深度不足,设计支护情况与现场实际开挖围岩情况不匹配,支护参数过强,造成工程浪费,支护参数过弱不能保证结构质量和安全。本文通过敦当试验段II标阿尔金山特长隧道初期支护钢管拱的灵活应用可有效解决隧道初期支护参数与围岩情况不相匹配的问题,尤其在围岩裂隙发育,结构破碎,宜掉块,且岩块有一定强度,沉降、收敛较小的石质隧道,配合监控量测,可极大地优化隧道初期支护参数,减少工程浪费,同时,保障现场施工安全和施工质量,也有效加快隧道施工进度,创造经济效益。     

隧道工程喷射混凝土施工质量控制分析

随着科学技术的发展,隧道施工技术也在超长、大跨度、防水、穿过不良地层等方面取得了长足的进步,涌现出了大量的科技成果,特别是作为新奥法施工工艺标志的锚喷构筑法更是如此,锚喷构筑法在技术上有速度较快、支护及时、施工安全;支护质量较好、强度高、密实度好、防水性能较好;省工,操作较简单,支护工作量减少;施工灵活性很大,可以根据需要分次喷射混凝土增加厚度,满足工程设计要求等优点,但在实际施工中有很多方面质量要点容易被忽视,从而影响了喷射混凝土施工质量。本文分析了喷射混凝土在隧道工程中的作用,对其施工过程中存在问题进行了探讨,供大家参考。     

水利工程中喷射混凝土支护施工技术

本文主要是介绍了水利工程中喷射混凝土支护施工技术,通过详细阐述了水利工程中喷射混凝土支护的特点和作用、以及支护对原材料和配合比的相关要求,为水利工程中喷射支护施工技术打下坚实的基础。     

公路工程隧道施工工艺浅析

公路隧道的施工原则是：施工中应少扰动围岩,尽快施作初期支护,及时量测和反馈,并使断面及早封闭。根据我国的隧道施工经验,可扼要地概括为“少扰动、早喷锚、勤量测、紧封闭”。具体地说,无论用钻爆或单臂掘进机开挖,必须严格控制,达到成型好、对地层扰动最小的要求,对开挖暴露面及时进行地质描述和喷锚加固,施工全过程应在对周边位移的监控下进行,并及时反馈、修正设计和施工方法。在软弱围岩地段应使断面及早闭合。文章结合实际论述了公路隧道修建的全过程中所用到的施工技术,也括隧洞土方的开挖,支护工程,隧道的通风,防排水系统等的施工工艺。     

地下工程喷射混凝土爆破振动安全标准研究

根据一维波动理论,通过分析应力波在不同介质中反射和透射的过程,研究了爆破振动应力波对巷道围岩和喷射混凝土的破坏作用。结果表明,在爆破振动应力波的作用下,对于坚硬岩体,支护结构的破坏主要由喷射混凝土的抗拉强度所决定;而对于软岩体,支护结构的破坏则主要由喷射混凝土与围岩的交界面的抗拉强度所决定。同时,通过研究爆破振动在围岩中的传播规律,得到了掘进爆破工程中喷射混凝土支护的安全距离,为地下掘进爆破工程施工以及喷射混凝土初期支护的设计提供了一定参考。     

缅甸巴鲁昌3号水电站引水隧洞不良地质段施工

对于极度破碎千枚岩区域、5类围岩的引水隧洞不良地质段,项目部在施工中采取了短进尺、人工配合机械开挖、型钢支撑联合喷锚支护的方法,并在一个循环开挖完成后及时进行强支护。这种方式有效地控制了洞室的垮塌,限制了围岩变形,保持了洞室的稳定。     

聚酰亚胺纤维与碳纤维缠绕复合气瓶性能对比研究

本文主要研究高性能国产聚酰亚胺纤维在复合材料气瓶上的应用,并表征其与进口碳纤维的性能差距.采用国产聚酰亚胺纤维进行缠绕成型工艺优化与复合材料性能测试分析,在测试数据及工艺优化基础上针对其进行了复合材料气瓶的强度设计.分别采用聚酰亚胺纤维、进口T300、T700以及T800碳纤维缠绕成型复合材料气瓶,进行水压爆破压强的测试,并引进声发射检测技术对其在水压过程中的损伤信号进行监测分析.结果表明聚酰亚胺纤维缠绕工艺性良好,与树脂界面结合优异,适用于湿法缠绕成型工艺.复合材料拉伸强度达到1 708 MPa,纤维的强度发挥率高达80%,相比于碳纤维复合材料其呈现出较好的断裂韧性,有利于减少复合材料气瓶在水压下的应力损伤.缠绕成型的聚酰亚胺纤维复合材料气瓶容器特征系数(PV/W)高达32.2 km,其在航空航天、医用、汽车、核工业等领域具有广阔的应用前景.     

NUMERICAL ANALYSES OF TUNNEL LININGS BY MEANS OF A VISCOPLASTIC MATERIAL MODEL FOR SHOTCRETE

This paper is concerned with the parameter identification, verification and selected applications of a 3D viscoplastic material model for shotcrete proposed by Meschke. The performance of the shotcrete model is evaluated by means of reanalyses of short-term and creep tests on shotcrete specimen. The most essential items of a viscoplastic cap model used for the representation of soil including the determination of the model parameters are also presented. Both models are employed in a 3D finite element simulation of the excavation of a single-track tunnel driven according to the New Austrian Tunnelling Method. Comparisons between in situ measurements and numerical results are presented.     

Impact resistance of fiber reinforced wet-mix shotcrete part 1: Beam tests

Shotcrete is often subjected to impact and other dynamic loads in service. These loads occur due to excavation blasting, traffic, sudden ground movements, rock bursts, and seismic activity. Sufficient anecdotal evidence exists of the ability of fiber reinforcement to enhance the resistance of shortcrete to such dynamic loads, but only limited real data exists in this regard. In this study, impact resistance of wet-mix shotcrete reinforced with ten different types of fibers was investigated using instrumented impact tests and compared with their quasi-static response. Both beam and plate specimens were tested. In Part 1 of this two-part paper, results with beam specimens are given. In Part 2 of the paper, data with plate specimens will be presented and correlated with the beam data reported here. Based on the beam tests, it is clear that fiber reinforcement is highly effective in improving the fracture energy absorption and toughness under impact loading. However, it is also apparent that the toughness or energy absorption capability of fiber reinforced shotcrete under impact loading is substantially different from that predicted by the standardized toughness tests carried out at slow, static rates of loading. Among the various types of fibers investigated, steel fibers were found to be the most effective in improving the resistance of shotcrete to impact, but the improvements depend on the geometry of the fiber. In the case of synthetic fibers, while polymeric macro-fibers of either polypropylene or polyvinyl alcohol adequately improve the resistance of shotcrete to impact loads, pitch-based carbon micro-fibers are relatively ineffective.     

Impact resistance of fiber reinforced wet-mix shotcrete Part 2: plate tests

In Part 1 of this paper, data on impact resistance of fiber reinforced wet-mix shotcrete obtained by testing beam specimens was presented. Ten different types of commercially available fibers were investigated. It was argued that since shotcrete in many applications is loaded dynamically, slow-rate static tests are not sufficient for a comprehensive characterization of its in-place performance. mance. It was also demonstrated that shotcrete is a highly stress-rate sensitive material, and its performance under impact is very different from that predicted by the slow-rate, quasi-static tests. From a standardization point of view, proper characterization of toughness and energy absorption capability of fiber reinforced shotcrete remains a challenge before the industry. Both beam and plate specimens are prescribed, but little understanding exists of the correlation, if any, between these two specimen geometries. In this paper, the same ten fiber types, tested in Part 1 using beam specimen, were investigated using plate specimens. As before, both static and impact tests were performed. Plate tests showed similar toughness enhancement due to fiber reinforcement, but the relative improvements between fiber types are not necessarily in agrcement with those indicated in the beam tests. Plate specimens were also found be less sensitive to changes in the rate of loading from static to dynamic. Considering these issues, and realizing that in practice shotcrete is often loaded in bi-axial bending, the use of plate specimens rather than beam specimens for the characterization of toughness of fiber reinforced shotcrete is recommended.     

Comparative evaluation of early age toughness parameters in fiber reinforced concrete

Early age strength development is a major consideration for design and construction processes such as the shotcrete mixtures used for tunneling applications. Adding the fibers to high strength concrete helps in resisting potential early age thermal and shrinkage cracking in addition to maintaining long-term strength. The post cracking tensile strength is one of the critical safety parameters to insure a safe level of ground support. Results of several bending tests on early-age fiber reinforced concrete are presented as load–deflection responses. A strain softening response is used to model the behavior of different types of fiber reinforced concrete and simulate the experimental flexural response. Closed form equations for moment–curvature response of a rectangular beam in conjunction with crack localization rules are utilized. As a result, the stress distribution that considers a shifting neutral axis can be simulated which provides a more accurate representation of the residual strength of the fiber cement composites. The analysis is performed to evaluate effects of age and fiber type on back calculated tensile stress strain response, along with experimental and simulated flexural load–deflection curves. The back-calculated tensile post cracking strengths are compared and correlated with the corresponding parameters used by ASTM, JCI, and RILEM methods and scale factors for the elastic methods are proposed which are in-line with the current fib Model Code. Caution must be exercised in application of results from the standard test methods due to the overestimation of the residual strength parameters that are based on elastic approaches.     

封闭型无溶剂聚氨酯超细纤维合成革基布的制备及性能

将聚酰胺6-碱溶性聚酯(PA6-COPET)海岛纤维非织造布与封闭型无溶剂聚氨酯(BSFPU)通过浸渍、碱减量和后整理等工艺制备了BSFPU超细纤维合成革基布.分析和探讨了BSFPU浸渍量对超细纤维合成革基布力学性能和卫生性能的影响,采用电子扫描显微镜对其微观结构进行表征.结果表明:海岛纤维经过减量后形成具有37根纤维...     

高强度南极磷虾蛋白/海藻复合纤维的制备与表征

以戊二醛为增强改性剂,利用湿法纺丝制备含有预埋增强剂的南极磷虾蛋白/海藻（AKP/SA）初生纤维,通过初生纤维纺丝线在线热交联技术实现热交联反应从而制得高强度南极磷虾蛋白/海藻（HAKP/SA）复合纤维。利用旋转黏度计确定了增强交联反应的热交联温度,研究了交联度对复合纤维微观结构以及吸湿性能的影响,测试了增强后复合纤维力学性能和结晶性能的变化。结果表明:80℃时戊二醛能有效发生热交联反应;AKP/SA复合纤维具有较好的吸湿性能,吸湿率为7.3%,随着交联度的提高,复合纤维的吸湿性能降低,吸湿平衡时间缩短;HAKP/SA复合纤维仍以非晶形态存在,表面存在不均匀的沟槽结构;力学性能测试表明增强后的纤维断裂强度提高了13%。