Controlling Structural Deformation of Surrounding Rock Passed by a Deep-Buried Tunnel北大核心CSCD

Layered rock masses with rapid and serious initial deformation and anisotropy regarding the spatial dis-tribution of the failure are encountered during the construction of many large and deeply buried tunnels on the Lan-zhou-Chongqing railway. It is difficult to deal with the resulting problems with conventional control measures, and additional support measures are frequently needed, which significantly affects construction. Focusing on this special large non-linear deformation, the failure mechanism of the large structural deformation of layered rock masses is thor-oughly analyzed by geological site surveys, laboratory tests, site tests and 3DEC discrete element numerical simula-tion. The research results show that high geostress induces rapid and strong squeezing deformation after excavation in low-strength rock masses, and anisotropy of the layered rock mass controls the stress redistribution after excava-tion and the asymmetrical distribution of tunnel section deformation. Based on the asymmetric deformation mecha-nism of the rock mass, a directional support measure for the disturbance anisotropy of the layered rock mass is pro-posed as a rock mass control to reinforce it in an active way. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

无车日活动公众参与的引导策略及信息传递

为了制定引导公众意识与行为转变的策略,尤其是对无车日的规划以及为将其应用于其他可持续性城市交通措施中提供指南.介绍了几种有关引导公众对于公共交通与其他可持续性交通方式的意识与行为转变的策略,重点介绍了公众目前与将来可以使用的可持续性交通方式,以及公众尤其是决策者对于城市交通问题的态度及其对于可持续性交通解决方案(如步行、骑自行车与使用公共交通工具等)的看法.最后,提出媒体是提高公众对于可持续性交通活动意识的有效渠道.     

Experimental study of the impact of structural geometry and wind direction on vehicle emissions in urban environment

Vehicle emissions inside an urban environment are investigated using a wind-tunnel under neutral atmospheric conditions. The urban environment was formed as street canyon model. The diffusion flow field in the boundary layer inside the street canyon was examined at different locations of varying geometry of the street and wind directions in the downwind distance of the leeward side of the street canyon model. The results show that the vertical velocity increases as the aspect ratio increases and with wind direction increases from θ = 90°. The pollutant concentration increases as the aspect ratio decreases. The pollutant concentration decreases as the wind direction increases from θ = 90°. The pollutant concentration distributions indicate that the variability of the structure, geometry and wind direction inside the street canyon are important parameters for estimating air quality in the urban street canyon.     

Urban highway congestion

This article examines urban highway congestion pricing in the instance in which it is not possible to levy a congestion toll on a major portion of the urban road system. This case is pertinent because of technical and/or political constraints. The article uses economic theory and numerical examples to show that the optimum second-best toll can vary appreciably from the optimal tolls in a regime in which efficient tolls can be imposed on all routes.     

深厚砂卵石地层超深竖井施工降水模型试验研究北大核心CSCD

富水砂卵石地层中基坑降水始终是工程界较大的难题,文章针对兰州强透水深厚砂卵石地层超深竖井降水进行了理论计算和模型试验研究,研制了一套有效的模型试验系统,配置了砂卵石土体相似材料,并重点研究了基底注浆加固对基坑降水的影响。研究结果表明:(1)黄河对基坑降水有重要的影响,靠近黄河一侧降水漏斗曲线陡直,远离黄河一侧降水漏斗曲线平缓;(2)基底注浆降低了水力梯度,提高基坑施工安全性,可有效减少基坑内抽水量,但对于坑外抽水量作用不大;(3)基底加固区渗透系数存在最优值,对于该工程,建议取1×10^(-6)m/s为加固区目标渗透系数。     

某富水断层隧道涌水治理方案优化分析及工程应用北大核心CSCD

以武九高速高楼山公路隧道为例,针对以断层破碎带为主控因素的隧道突水治理问题展开数值分析研究。基于FLAC 3D有限差分法及流固耦合分析原理,研究了导水洞排水、注浆堵水和排堵结合等不同治理方式对隧道涌水量及围岩稳定性的影响。结果表明:对于富水断层隧道发生A、B级别的大量涌水时,建议同时采取导水洞排水、注浆堵水的排堵结合措施,导水洞设置在近断层处,且与隧道相对距离为0.75(D+l),注浆圈厚度控制在7 m以内,注浆圈相对渗透系数比不超过10,既能降低涌水量,又能保证围岩的稳定性;对于C级涌水隧道,可采取注浆措施,注浆厚度不低于3 m,相对渗透系数不低于20;对于D级及以下涌水隧道,采取常规抽排水措施即可。     

Analysis of the application and development of integrated electric power technology for unmanned ships北大核心CSCD

近年来,随着动力、信息等技术的不断发展,无人船在反水雷、反潜、电子战、海上安全、海上拦截等军用领域凸显出越来越大的优势。为此,首先阐述无人船及其动力技术的发展概况,明确综合电力系统已成为中大型无人船的重要发展趋势,然后介绍综合电力系统在有人/无人平台的应用情况,提出设备尺寸、重量和振动噪声控制等问题是综合电力系统应用于无人平台的研究重点,最后阐明无人平台综合电力技术的发展趋势,指出综合电力系统智能化运行、高性能电机材料、复杂电机系统信息感知、电力电子器件与系统、高性能电能变换和高效储能是无人平台综合电力技术的关键科学问题。     

Development and prospects of key technology for submarine atmospheric environment control北大核心CSCD

Air regeneration, harmful gas purification and atmospheric composition monitoring are the key technologies of submarine atmospheric environment control systems. After years of development, China has made great progress in such systems, which have developed from ensuring the safety requirements of submariner and equipment operation to ensuring the health of submariner and reliability of system for long-term underwater operation. This paper reviews the development history of submarine atmospheric environment control technologies and introduces their future development prospects. The developers of integrated atmospheric environment control technology should learn from foreign submarine and aerosphere equipment technologies, which aim to support long-term submerged operation and comfort demands, and better adapt to future submarine technology development and evolving mission, in order to constantly enhance the level of submarine cabin air quality of the Chinese navy. © 2022 Journal of Clinical Hepatology. All rights reserved.     

CMC改性海水泥浆性质变化及砂地层成膜试验研究北大核心CSCD

为探究泥水盾构穿越海底砂地层时羧甲基纤维素钠(CMC)对海水泥浆性质及成膜效果的影响,配制不同CMC掺量的海水泥浆,分析泥浆泌水率、黏度、Zeta电位等性质的变化情况,并开展了泥浆渗透成膜试验。研究结果表明:相对于海水泥浆,加入CMC后的泥浆黏度逐渐增大,2h泌水率显著减小,形成的泥膜中结合水含量逐渐变大,泥膜渗透系数减小至4.03×10^(-8)cm/s;改性海水泥浆中粒径小于75μm的细颗粒含量显著增加,静置24h后,泥浆上部呈现浑浊,下部依然存在较严重的沉淀;当CMC掺量达到0.16%时,改性海水泥浆2h泌水率小于10%,成膜渗透流量小于0.01m^(3)/m^(2),可以保证泥浆短期稳定性并形成致密泥膜。     

Optimisation and heuristic approaches for assigning inbound containers to outbound carriers

Due to economical and/or geographical constraints, most of the time overseas containers cannot be directly shipped to their destinations. These containers visit transhipment ports where they are first unloaded and temporarily stored and then loaded onto smaller vessels (feeders) to be transported to their final destinations. The assignment of these containers to outbound vessels necessitates several factors to be taken into account simultaneously. In this paper, we develop a mathematical model to reflect multiple objectives with priorities and to assign these containers to different vessels at the transit container port terminal. Although we solve a single-objective (with the weighted sum of objectives) mathematical model to optimality, we also propose two heuristic approaches to solve this complex problem for a transit agency. The first heuristic is shipment based and has four variants differing in how the opportunity costs of the assignments are calculated. The second greedy heuristic is trip based, where the goal is to maximise the capacity utilisation of the vessels. The heuristics return very promising solutions in ignorable computational times. We also provide real-life cases and present our conclusions.