改进的小波神经网络在桥梁施工控制中的应用

桥梁线形的预测和调整对于大跨径桥梁施工控制具有重要的指导作用。利用小波分析技术对实测数据进行消噪处理,将BP神经网络与Morlet小波结合起来,建立相应的小波神经网络模型,并对桥面标高偏差进行预测。结果表明,采用该方法对桥梁施工控制有较好的预测精度。     

应力剪胀对浅埋偏压隧道破坏面形状的影响

采用有限差分软件,对浅埋偏压单线铁路隧道和四车道公路隧道进行数值模拟。研究了围岩的松动土体力学行为,主要考虑应力剪胀对浅埋偏压隧道破坏面形状的影响,并将数值模拟的结果与规范理论解进行了比较。结果表明：剪胀角对浅埋偏压隧道围岩位移和破坏面形状有较大影响。因此,在确定浅埋偏压隧道围岩松动压力时应该考虑剪胀对破坏面形状的影响。     

偏压连拱隧道施工顺序优化研究

以某隧道为例,从满应力设计的基本思想出发,考虑隧道本身结构及洞周围岩的受力和稳定性．提出了一个反映中墙和支护结构及围岩在施工过程中的受力的综合优化模型,对偏压连拱隧道的施工顺序进行了优化。并通过工程实例分析,验证了所提出优化方法的可行性,对类似的偏压连拱隧道工程的施工具有指导意义和参考价值。     

洞口段浅埋偏压隧道新型防护结构及其简化计算方法

针对现有洞口段浅埋偏压隧道支护结构在施工时所存在的容易坍塌、整体位移过大等问题,在充分发挥抗滑桩、锚索和管棚优点的基础上,利用交叉施工和分时注浆方法,提出一种洞口段浅埋偏压隧道新型防护结构。建立地形偏压下防护结构的简化分析模型,并利用M法对防护结构在地形偏压下的内力和位移进行求解;然后利用变形协调条件对结构的内力和位移进行修正,最终得出该新型结构在地形和施工偏压联合作用下的受力和变形状况。结合算例,对新型防护结构的内力和位移分布规律进行分析,并将计算结果与ADINA模拟结果进行对比,验证了简化计算方法的可靠性,为该新型结构的分析与设计提供了理论基础和依据。     

偏压连拱隧道围岩变形的现场监测与分析研究

结合宜(宾)水(富)高速公路鞋底坡双连拱隧道施工过程,通过对偏压连拱隧道的围岩变形进行现场监测与分析,获得了隧道围岩在地层偏压条件下。各施工阶段的地表沉降、拱顶下沉和水平收敛情况,有效地控制了隧道围岩变形。通过对量测结果的对比、分析得出：在偏压连拱隧道施工过程中,隧道初期支护变形整体由左洞向右洞方向偏移;对隧道围岩变形影响最大的工序发生在隧道旌工由单侧过渡到双侧施工时。在施工过程中偏压连拱隧道的现场测试与分析,不仅为隧道的支护体系设计优化提供依据,而且还可以指导隧道现场施工,所得的数据和结论可为同类隧道的设计,施工和研究提供有益的借鉴和参考。     

泡桐坪隧道进出口浅埋段偏压条件下施工

浅谈泡桐坪隧道进出口堆积体及严重风化岩段在洞口浅埋、偏压条件下的隧道施工技术,重点对该段的地表加固、小导管施工、堆积体及强风化岩段的开挖与支护等技术作了详细阐述。     

基于电池组件PID效应的光伏逆变器设计

阐述了光伏电池组件电势诱导衰减效应（PID）的产生机理、衰减模式,通过对光伏逆变器的特殊化设计降低了电池组件的PID效应,从而提高光伏系统发电效率。     

梅树岭隧道洞口段浅埋偏压施工技术

以京福铁路客专(闽赣段)梅树岭隧道为工程背景,针对隧道洞口浅埋偏压段的施工,从方案确定及施工过程中所采取的措施出发,依据施工状况提出具体的处理措施。实践证明,所采取的措施及处理方法保证了隧道洞口的施工安全及施工进度。     

Selection bias in build-operate-transfer transportation project appraisals

Recent empirical studies have found widespread inaccuracies in traffic forecasts despite the fact that travel demand forecasting models have been significantly improved over the past few decades. We suspect that an intrinsic selection bias may exist in the competitive project appraisal process, in addition to the many other factors that contribute to inaccurate traffic forecasts. In this paper, we examine the potential for selection bias in the governmental process of Build-Operate-Transfer (BOT) transportation project appraisals. Although the simultaneous consideration of multiple criteria is typically used in practice, traffic flow estimate is usually a key criterion in these appraisals. For the purposes of this paper, we focus on the selection bias associated with the highest flow estimate criterion. We develop two approaches to quantify the level and chance of inaccuracy caused by selection bias: the expected value approach and the probability approach. The expected value approach addresses the question “to what extent is inaccuracy caused by selection bias?”. The probability approach addresses the question “what is the chance of inaccuracy due to selection bias?”. The results of this analysis confirm the existence of selection bias when a government uses the highest traffic forecast estimate as the priority criterion for BOT project selection. In addition, we offer some insights into the relationship between the extent/chance of inaccuracy and other related factors. We do not argue that selection bias is the only reason for inaccurate traffic forecasts in BOT projects; however, it does appear that it could be an intrinsic factor worthy of further attention and investigation.     

山岭隧道浅埋偏压段综合治理技术浅谈

贵广铁路贺街隧道进口位于浅埋偏压地段,前期施工过程中各种地质灾害屡有发生,并且多次发生大型滑塌、初支侵限、结构大变形现象,对施工进度、安全、质量均产生不同程度影响,为山岭隧道浅埋偏压施工困难之典型。本文系统介绍了如何采取措施确保结构稳定性和综合治理措施以及受力转换合理性,实践证明隧道安全施工得以保证。