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公路隧道二次衬砌纵向裂缝非线性数值模拟研究 总被引:2,自引:1,他引:1
已建隧道普遍存在衬砌开裂现象,裂缝的存在会降低隧道衬砌的承载能力.文章为研究带裂缝隧道衬砌的力学性能,提出了塑性地压、松弛土压、偏压等三种受力裂缝数值模拟的荷载施加模式;分析了几种常见裂缝模型的原理及适用性,并且基于钢筋混凝土有限元非线性分析理论,利用分布裂缝模型进行不同荷载模式下隧道二次衬砌开裂至破坏的全过程分析;通过计算得出了不同加载方式下裂缝的发展及分布规律.研究结果可为隧道衬砌裂缝成因判断及二次衬砌加固改造提供理论支撑. 相似文献
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《现代隧道技术》2017,(2)
在对湖北省谷竹高速公路隧道二次衬砌完整性的调查过程中,发现片岩隧道普遍存在二次衬砌开裂现象。为了合理科学地治理开裂问题,文章通过对沿线48座隧道的调查分析,归纳和总结出该区段隧道二次衬砌开裂的6大特征:片岩隧道二次衬砌开裂现象普遍;开裂位置主要位于进、出口浅埋段;先行洞裂缝数量多于后行洞,开裂形式主要为斜向开裂;在发生大变形、塌方等地段二次衬砌容易开裂;开裂的时间一般在二次衬砌施作5个月后。在此基础上,通过室内试验与现场调查共同分析二次衬砌开裂的成因机理,并得出原因:片岩的强度低,遇水易软化;洞口处的浅埋段成拱性差;偏压现象普遍;仰拱不均匀沉降;岩石受地下水的影响及岩体的蠕变效应。最后,根据开裂原因提出相应的增加围岩级别、加强洞口施工及重视小净距中夹岩稳定设计等建议措施,为类似工程提供相关参考依据。 相似文献
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为研究裂缝数量对隧道衬砌结构承载性能及安全性的影响机理,基于断裂力学理论建立带裂缝衬砌内力计算模型,推导双裂缝情况下应力强度因子计算公式,并分析开裂衬砌结构内力和稳定系数的变化规律,不同数量裂缝对衬砌结构内力的影响规律以及开裂部位拉应力的变化情况。结果表明:与拱顶存在1条裂缝相比,存在2条裂缝时承载能力仅降低1.35%,稳定系数降低6.9%;存在3条裂缝时承载能力降低2.26%,稳定系数降低8.1%。拱顶存在多条相近裂缝时,其中一条裂缝对其他裂缝有一定闭合作用,不会加速裂缝的扩展。 相似文献
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碳纤维布在连拱隧道衬砌裂缝病害治理中的应用 总被引:1,自引:0,他引:1
延安至安塞高速公路墩山连拱隧道主体工程完工后,衬砌出现了不同程度的裂缝和渗漏水等病害,通过对衬砌裂缝特征、产生原因的分析,并根据裂缝的开裂程度与发展规律,采用碳纤维布对隧道衬砌裂缝进行了局部修复和整体加固补强。由于在施工过程中严格控制施工工艺和施工质量,达到了预期效果。通过碳纤维加固模拟和监测表明:衬砌裂缝得到了有效控制,支护受力处于安全状态,围岩稳定,碳纤维布加固效果显著。 相似文献
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《现代隧道技术》2020,(4)
隧道衬砌模型试验是一种研究衬砌力学性能和开裂行为、指导隧道衬砌结构设计优化与维修加固的重要试验手段。文章介绍了自主研发的隧道衬砌多点独立加载试验系统,该系统能够按照二次衬砌荷载的分布形态和量值,对大尺寸衬砌模型的15个关键位置进行低速高精度加载,实现复杂受力条件下衬砌结构受力变形和开裂行为的物理模拟。以某黄土隧道浅埋段衬砌断面为试验背景,基于二次衬砌受荷现场监测结果,利用该试验系统进行了相似比为1∶10的二次衬砌受力变形模型试验,归纳总结了二次衬砌的开裂特征与应变变化规律。结果表明,该系统加载效果良好,加载精度满足工程试验要求。其试验结果有助于预测二次衬砌裂缝病害发展,明确衬砌加固重点区域,可为衬砌的维修加固提供帮助。 相似文献
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《现代隧道技术》2017,(3)
裂缝在公路运营隧道衬砌结构中普遍存在,其稳定与否直接关乎隧道的运营安全,而通过监测手段分析预测裂缝的发展态势是一种最为直观和有效的手段。文章针对目前衬砌裂缝监测成果偏少这一现状,依托某二级公路隧道工程,主要对以下内容进行研究:从裂缝类型、所处位置及围岩级别、裂缝的几何特征3个方面分析了衬砌裂缝的分布规律;采用光栅光线传感器对选取的12条典型衬砌裂缝进行了为期2年的监测工作,监测成果表明衬砌裂缝发展规律可大致分为平稳型、周期性变化型、增长型及闭合型4种,且从裂缝几何特征参数的监测数据可以看出,多数裂缝处于一种相对稳定的可控状态,对隧道结构稳定性影响较小;从勘查设计、施工以及运营管理3个环节对隧道衬砌裂缝成因进行了系统分析,并据此提出了隧道衬砌裂缝预防措施;对衬砌裂缝的治理,建议采用"先监测、后分类、再选择治理措施"的治理理念。研究成果可为国内外类似隧道工程衬砌裂缝评估及防治提供参考与借鉴。 相似文献
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文章针对复合式衬砌在防水方面存在的问题,通过结构模型实验,对隧道复合衬砌卷材防水板分区防水的关键技术进行研究,对其防水效果进行综合评价,提出了分区防水的原则、设计参数和确保分区成功的拱顶注浆参数,同时为隧道分区防水的施工工艺提供确切的试验依据.阳宗隧道富水段工程运用分区防水技术,实现了隧道富水段不渗不漏目标,防水效果优异. 相似文献
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隧道衬砌厚度分布规律及结构可靠性分析 总被引:4,自引:1,他引:4
通过对新建公路隧道衬砌厚度现场的测试,运用数理统计方法总结了厚度变化的规律,进行了结构可靠度分析,并分析其对工程成本的影响. 相似文献
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深埋高水位山岭隧道作用于衬砌外表面的水压力计算方法 总被引:5,自引:1,他引:5
文章针对深埋高水位山岭隧道,通过把含水地层视作无限含水地层和半无限含水地层(即考虑边界的影响)对作用于隧道衬砌外表面的水压力分别进行了分析论述,并推导出了水压力计算公式,同时给出了层状岩层垂直于层面渗流的等效渗透系数的计算方法,可供类似工程设计和施工中参考. 相似文献
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The demand for rail freight transportation is a continuously changing process over space and time and is affected by many quantitative and qualitative factors. In order to develop a more rational transport planning process to be followed by railway organizations, there is a need to accurately forecast freight demand under a dynamic and uncertain environment. In conventional linear regression analysis, the deviations between the observed and the estimated values are supposed to be due to observation errors. In this paper, taking a different perspective, these deviations are regarded as the fuzziness of the system's structure. The details of fuzzy linear regression method are put forward and discussed in the paper. Based on an analyzes of the characteristics of the rail transportation problem, the proposed model was successfully applied to a real example from China. The results of that application are also presented here. 相似文献
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The Harbor Maintenance Tax is a fundamentally flawed maintenance funding mechanism for the critical US port system. Three alternatives were analyzed. User fee rates were estimated for either a national or regional tonnage based fee. Our results indicate that maintenance cost recovering regional fees could vary widely from about 10 cents per tonne to nearly 80 cents per tonne. A national rate would be about 30 cents per tonne. The large regional differences and affects on bulk shippers are likely to make implementing and maintaining cost recovering tonnage based fees infeasible. Two other mechanisms are considered. One possibility is to abolish the HMT without a replacement mechanism. The obvious strength of this approach is its simplicity, the weaknesses is that it is not budget neutral. Another possibility is to increase the federal diesel tax rate. One strength of the approach is the reasonable rate increase required to recover port maintenance costs (estimated between 0.278 and 0.315 cents per liter). An additional strength is that relatively inefficient fuel users will either make the largest share of the additional payments or the freight will shift modes to one that is more efficient. One weakness is that the rate has been unchanged since 1997, this points to the political difficulty involved in passing such a rate increase. 相似文献
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Mathematical model for optimising the sequence for clearing snow from the manoeuvring area during winter operations 下载免费PDF全文
This article considers the optimisation of the sequence for clearing snow from stretches of the manoeuvring area of an airport. This issue involves the optimisation of limited resources to remove snow from taxiways and runways thereby leaving them in an acceptable condition for operating aircraft. The airfield is divided into subsets of significant stretches for the purpose of operations and target times are established during which these are open to aircraft traffic. The document contains several mathematical models each with different functions, such as the end time of the process, the sum of the end times of each stretch and gap between the estimated and the real end times. During this process, we introduce different operating restrictions on partial fulfilment of the operational targets as applied to zones of special interest, or relating to the operation of the snow‐clearing machines. The problem is solved by optimisation based on linear programming. The article gives the results of the computational tests carried out on five distinct models of the manoeuvring area, which cover increasingly complex situations and larger areas. The mathematical model is particularised for the case of the manoeuvring area of Adolfo Suarez Madrid—Barajas Airport. Copyright © 2016 John Wiley & Sons, Ltd.
- Highlights
- Optimal sequence for clearing snow from the manoeuvring area of an airport.
- Contains optimising algorithms solved using CPLEX LP‐based tree search.
- Restrictions on partial fulfilment of operational targets applied to subsets of significant stretches, used for planning the operation of snow‐clearing machines.
- Model applied to the case of the manoeuvring area of Adolfo Suárez Madrid Barajas Airport.
- Conclusions are given on the results of the computational tests carried out. There are five models of the manoeuvring area which cover increasingly complex situations and larger areas.
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Seeing the trend for public accountability of road administrations and noting the many reform efforts undertaken in transport sectors around the world, the OECD established a Scientific Expert Group on Performance Indicators for the Road Sector in 1996 to provide its member countries a framework for assessing road administrations' performance. The results of the Expert Group's work is presented in this paper.Fifteen indispensable, forty primary, and thirty-five secondary indicators are proposed to portray the road sector from different perspectives. They are designed to be changed in response to human needs and technological development and supplemented by country specific indicators. In keeping with this approach and in support of one of the maxims of the Expert Group that 'useful performance indicators are those which are used', an application in the form of a Field Test is now in progress by an OECD task force.The Performance Indicators proposed are grounded in a mental model adopted by the Expert Group. This model is management by results model, and is useful as a theoretical tool in the many highly fluid contexts in which restructuring is moving forward. In the model, the products and services are judged by standards or criteria; outcomes – derivatives of products and services through user interface – are judged relative to objectives and user satisfaction. The achievement of objectives, however, is not proposed as the only or even primary basis of evaluation. The situation is more abstract and complex. Therefore, the various uses of Performance Indicators – including the opportunities to assist road administrations in becoming learning organizations – are given much emphasis in the paper. The views and conclusions in the paper are those of the author and should not be attributed to the World Bank or its affiliated organizations. 相似文献