荷坳隧道四洞小净距段支护结构设计研究北大核心CSCD

多洞空间小净距隧道支护结构参数量化设计与安全性分析是当前设计中的一大难题。文章针对深圳机荷高速公路荷坳隧道四洞小净距段的设计,采用总安全系数法对四洞的开挖与支护模式、各洞的开挖顺序及支护参数进行了研究比较,并采用隧规荷载-结构法、增量法、地层-结构法对支护结构的安全系数进行了对比计算,得出以下结论:(1)提出了基于总安全系数法原理的多洞空间小净距隧道设计方法;(2)根据总安全系数法得出了荷坳隧道四洞小净距段应采用“先行洞二次衬砌完成后再开挖下一孔隧道”的开挖与支护模式,且应按洞1→洞2→洞3→洞4的开挖顺序施工;(3)隧规荷载-结构法、增量法、地层-结构法虽无法得出结构的总承载安全系数,但在一定程度上可以反应部分支护结构的安全性。     

圆形直管湍流粗糙管区的摩擦因数计算

提出了简单适用的管路摩擦因数λ的计算方法,解决了柯尔布鲁克-怀特(Colebrook-white)公式中隐函数不易计算的问题,该方法计算精度高于其他现有简化公式;在10-8≤ε/d≤0.05、3000≤Re≤108时,该方程的计算结果与原Colebrook-White方程的平均相对偏差为0.3315%,最大偏差不超过2.0%。     

绝热材料下沉对蒸汽管道热损失的影响

文中从绝热材料下沉的角度，利用形状因子法对高温蒸汽管线保温问题进行了探讨。通过理论分析和实验测试，得出了“复合硅酸盐保温涂料＋复合硅酸盐保温型材＋复合硅酸盐保温涂料”的保温结构，可有效改善绝热材料的下沉问题。     

On Safety in Dismantling Temporary Strut of Super-large Tunnels with Double-layer Primary Support北大核心CSCD

More and more multiple-track tunnels and super-large section tunnels have been built, and disman- tling of temporary strut is a weak point of the whole structure during force transfer when the secondary lining is con- structed. It is significant to guarantee structure safety during dismantling of temporary strut. Little systematic re- search on safety in dismantling of temporary strut of the super-large section tunnel with double-layer primary support has been conducted, so the internal force and security of the two-layer primary support of the Xinkaotang tunnel were analyzed by a numerical analysis and site measurement, and it proves the effect of two-layer primary support on the safety during strut dismantling. The research results indicate that: (1) with constant support thickness and one-time longitudinal dismantling length, the safety factor of secondary primary support is larger than that of the first primary support, and the safety factor of the first primary support is larger than that of the single-layer primary support. Change range of safety factor for the first primary support is smaller than that of the single-layer primary support, and the safe factor for the single-layer primary support is smaller than that of the secondary primary support; (2) with the same support pattern, the safety factors increase firstly and then decrease with an increase of the onetime dismantling length. The calculated results of various cases show that the reasonable one-time dismantling length for this project is about 9 m. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Subsidy and public transit performance: A factor analytic approach

The need to measure and evaluate transit system performance has led to the development of numerous performance indicators. However, depending upon the indicator, we oftentimes reach different conclusions regarding transit system performance. The research reported in this paper uses factor analytic methods to generate a set of underlying attributes (factors) that capture the performance of public transit systems in Indiana. Similar to what is reported in the literature, this study finds three attributes that best describe transit system performance: efficiency, effectiveness, and overall performance. Based upon systemsÕ factor scores, the study finds that systems scoring highly on one attribute generally perform well on the remaining attributes. Further, there is an inverse relationship between system performance and subsidies, a finding that supports performance based subsidy allocations.     

地质轴压裂纹倾角应力强度因子的光弹性实验研究

岩爆是采矿和隧道开挖等地下工程的一大地质灾害,并且具有猛烈和瞬发的特性,其复杂的机理已经成为众多工程师和研究人员的研究课题,同时在工程中具有很深远的意义。该文通过将光弹性实验的方法和断裂力学相结合,讨论了岩体内裂纹角度变化对裂纹尖端应力强度因子的影响,同时分析了对远场应力的影响。     

国道217线天山公路溜砂坡病害形成机制分析及防治对策

通过天山公路溜砂坡病害形成条件和影响因素的分析,依据野外观察和室内试验数据,提出了溜砂坡坡体失稳的动力学机制及形成演化规律;同时以K612+750～K613+850特大溜砂坡群为例,对该溜砂坡群的变形破坏机理进行了分析,并基于模糊数学理论及层次分析法对该溜砂坡的危险性进行了模糊评判,提出了治理溜砂坡的初步对策。     

减水剂与水泥适应性研究现状

减水剂与水泥的适应性是一个相当复杂的问题,即使它们都完全符合相关标准的规定,但同时作为配置混凝土的原材料时,就可能出现不适应的现象。为了在实际工程中得到更好的应用,文章从减水剂与水泥两方面讨论了影响它们之间适应性的因素,并提出改善适应性问题的措施。     

基于路基工程地质分析原理的灾害识别

通过路基地质灾害的实地调查研究,提出了路基工程地质分析原理,分析了它与路基地质灾害识别之间的基本关系,并以实例说明了路基工程地质分析原理在路基地质灾害识别中的应用。     

基于FLAC~(2D)的膨胀土边坡稳定性影响因素分析

膨胀土滑坡问题在工程建设领域出现的越来越多,准确地了解膨胀土土体各项参数对其稳定性有何影响显得尤为重要。以宿州至扬州高速公路天长段膨胀土边坡实例为计算模型,利用正交试验探讨了边坡土体天然密度、粘聚力、内摩擦角、弹性模量和泊松比对其稳定性的影响,得出了一些有意义的结论,为工程建设中膨胀土边坡设计和治理提供参考。