深埋大断面黄土隧道初期支护受力特征分析

为避免初期支护局部破坏对深埋黄土隧道安全产生危害,依托甘肃省境内早胜3号隧道施工开展深埋大断面黄土隧道初期支护受力规律的现场试验研究。通过埋设振弦式传感器对围岩与初期支护接触压力、喷射混凝土应变、钢拱架应变、相邻钢拱架间作用力进行监测,同时建立模拟隧道施工的有限元计算模型,分析得到初期支护内力分布特点。结果表明： 1) 初期支护受力随时间表现出迅速增长—缓慢增长—逐渐稳定的特点,曲线在二次衬砌闭合12 d后基本稳定; 2)应力空间分布上部大下部小,偏压特性明显,荷载理论计算值偏小; 3) 拱顶及边墙区域为初期支护薄弱部位,需采取措施并加强监控量测; 4)数值计算表明锚杆末端轴力较小,设计中可考虑适当缩短锚杆长度。     

压气条件下泥膜进气值测量试验研究

在压气条件下,进气是泥膜透气失效的起始点。为测量并研究泥膜在气压下的进气压力值（进气值）,通过自制的试验装置,在不同压气条件下对3种泥膜进行进气值测量试验。试验结果表明： 1)由闭气排水与固结排水的差值可以辨别泥膜是否进气,得到泥膜进气值; 2)采用泥膜特征孔径D90/2代入推导公式可近似计算泥膜进气值; 3)泥膜在不同压气条件下进气值不同,增压速率越低,泥膜进气值越大; 4)在较快和较慢的增压速率下存在进气值变化趋于稳定的现象,最大进气值为最小值的2倍以上。     

秦岭天台山大断面高速公路隧道降尘除尘方案研究

为解决由于隧道施工断面大、在开挖过程中产生的粉尘难以通过施工通风排除的问题,对秦岭天台山隧道（双向6车道）施工过程中钻孔、爆破、出渣、喷浆等不同工况下的隧道粉尘质量浓度进行现场实测,并根据现场实测结果,对隧道内各工况施工粉尘分布特性进行数值模拟研究,提出适合于大断面隧道施工的粉尘控制措施。现场测试结果表明,出渣和喷浆工况下,粉尘质量浓度超过规范要求数倍。通过数值模拟得到： 1）靠近掌子面40 m区域内粉尘质量浓度不稳定,下降趋势不明显; 2）在布置风管时,风管末段至掌子面距离建议取为60~80 m,以保证新鲜风以较大的喷射面抵达掌子面; 3）建议采用附壁风筒降尘+车载除尘方案,除尘效率达95%,能有效处理隧道各区域粉尘,且对施工造成的影响小。     

隧道爆破信号主分量特征提取与毫秒延期识别研究

为了准确揭示隧道爆破振动信号所包含的反映爆破特征参数的重要信息,通过EMD分解与交叉小波变换组合分析方法对实测爆破信号进行分析,得到各分量与原信号的相关性系数,从而准确判别出信号的主分量。再依据相关性系数对包含主分量在内的相关分量重组并进行Hilbert变换取模值,精确识别出隧道采用的各段别雷管的毫秒延期时间。结果表明： 组合方法确定的主分量及相关分量重组信号能够突出爆破信号的主要特征,对隧道爆破信号的分析效果好。     

基于气动效应的特长隧道断面优化探讨

铁路隧道净空面积的确定,不仅应考虑隧道建筑限界和机车车辆限界,还要考虑列车通过隧道时诱发的空气动力学效应。基于一维、可压缩、非定常的流动假设,推导得到车内瞬变压力、洞口微气压波和空气阻力计算公式,并结合这3个指标对现有城际铁路、高速铁路隧道设计规范进行论证和优化。结果表明： 针对大于10 km的特长隧道,在一定长度范围内,且在提高列车密封水平、增加洞口微气压波缓冲结构的情况下,可对特长隧道净空断面进行优化。     

A Pareto-improving hybrid rationing and pricing policy with multiclass network equilibria

This paper extends the work on Pareto-improving hybrid rationing and pricing policy for general road networks by considering heterogeneous users with different values of time. Mathematical programming models are proposed to find a multiclass Pareto-improving pure road space rationing scheme (MPI-PR) and multiclass hybrid rationing and pricing schemes (MHPI and MHPI-S). A numerical example with a multimodal network is provided for comparing both the efficiency and equity of the three proposed policies. We discover that MHPI-S can achieve the largest reduction in total system delay, MHPI can induce the least spatial inequity and MHPI-S is a progressive policy which is appealing to policy makers. Furthermore, numerical results reveal that different classes of users react differently to the same hybrid policies and multiclass Pareto-improving hybrid schemes yield less delay reduction when compared to their single-class counterparts.     

Formulating cargo inventory costs for liner shipping network design

This study examines how to incorporate the inventory costs of containerized cargoes into existing liner service planning models such that the designed networks could be improved while not causing extra modeling/computational burden. Two approaches are compared: (i) not considering the inventory costs at all and (ii) incorporating the inventory costs associated with onboard time and those related to transshipment by assuming a fixed connection time. The two models are compared with the ideal model capturing the exact inventory costs on a route choice problem and a capacity planning problem based on extensive randomly generated and practical numerical experiments. The results show that: first, ignoring the inventory costs in service planning models may lead to network design with much higher costs (poor network design decisions); second, in service planning models assuming weekly frequency, the inventory costs associated with onboard time could be formulated exactly, and those related to the connection time of weekly services could be approximated by assuming fixed connection time of 3.5 days for ports with 1 day’s minimum connection time and 4.5 days for ports with 2 days’ minimum connection time.     

A logit-based model for measuring the effects of transportation infrastructure on land value

Mutual interactions between transportation and land use have long been debated. Despite progress made in computational technology, the study of these interactions is not adequately developed. The most important aspect of such interactions is given by the changes in land values due to changes in transportation infrastructures. We consider the behavioural features of these interactions along with the constraints on the land and/or zoning restrictions and propose a reliable model for the first time to predict land value changes with respect to changes in transportation facilities and accessibility. The proposed model is a logit-based mathematical programming methodology where the relative price of land is predicted with respect to transportation accessibility, neighbourhood amenities, location premium, availability of land, and zoning regulations. A real-world case study is used to exhibit the applicability of the proposed methodology and demonstrate the efficacy of the algorithms and procedures.     

波浪动力对开敞淤泥质海岸深水航道边坡稳定性的影响

开敞淤泥质海岸深水航道边坡的稳定性关系到航道的基建及维护费用,是航道工程设计中最重要的问题之一。以连云港港徐圩港区10万吨级航道为研究对象,采用在连云港海域应用较为成熟的波浪数学模型推算的波要素成果,研究中浪、大浪对徐圩10万吨级航道边坡稳定性的影响,并利用边坡实测地形资料进行分析。结果表明,从波浪动力的角度来看,徐圩10万吨级航道设计边坡的坡度取值是合理的,本海域的波浪动力不会对航道边坡的稳定性造成不利影响。     

波浪作用下斜坡式护岸反射系数试验

通过物理模型试验,研究在不规则波作用下,斜坡坡度、波陡、扭王字块体的摆放方式对反射系数的影响,并将实测的反射系数与Seeling公式、Sutherland公式和Van der Meer公式的计算值进行比较。结果表明斜坡坡度与反射系数成正比,波陡与反射系数成反比,扭王字块体的摆放方式对反射系数的影响不大,试验值普遍比3种公式的计算值要大,其中试验值与Seeling公式的计算值相差较小。