Application of Vertical Freezing Technique in the Deep-buried Mountain Railway Tunnel北大核心CSCD

The strata of Chengershan tunnel is mainly consist of the slightly cemented tertiary sandstone, the tun⁃ nel body passes through F 2 fault core zone. Geological disasters of mud outburst, sand gushing and extrusion of work face occurred several times during tunnel construction, so the risks are very high. In view of the core zone of F 2 fault with high pressure and abundant water, a variety of construction schemes were compared and analyzed in terms of technology, feasibility and safety, and vertical freezing technique was used for stratum reinforcement in the railway tunnel for the first time, furthermore the freezing scheme and tunnel support measures were studied, providing refer⁃ ence and guidance for similar tunnel construction.Mountain railway tunnel; Fault zone; Tertiary sandstone; Vertical freezing technique; Application © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

基于遗传算法的盾构隧道管片接头刚度反演研究北大核心CSCD

梁-弹簧模型在管片衬砌结构计算中应用较广泛,目前接头刚度取值方法主要有模型试验法及经验取值法,模型试验法耗时长、成本高昂,而依据经验取值难免存在一定主观性。鉴于此,利用C++编程语言,基于遗传算法开发了盾构隧道管片结构位移反分析程序,首先通过弹性模量值反演算例,得出反演值与理论值误差为1.4%,验证了算法和程序的可行性。利用程序将反演接头刚度值与实际设计案例管片接头刚度值进行对比,反演计算结果表明:正弯矩下管片环向接头转动刚度值反演误差为2.6%,负弯矩下管片环向接头转动刚度值反演误差为4.3%。     

Transport reviews prize

Bombay, the commercial capital of India, is suffering from traffic thrombosis. Bombay used to be an attractive city some three decades ago and was commonly referred to as ‘Bombay the Beautiful’. The picture is now, however, the opposite extreme.

The way Bombay has grown, an underground railway is no doubt justified. Unfortunately, the economy may not be able to afford it for many years to come. Low cost measures have therefore to be adopted like (a) development of land use with a view to controlling the traffic demand itself; (b) discouraging further growth in and around the existing congested central business district; (c) establishment of a counter‐magnet; (d) conversion of the mono‐centric pattern to a poly‐nucleated structure; (e) better pedestrian facilities; (f) intermediate public transport; (g) traffic management measures to maximize available road capacities; (h) bus priority measures; (i) creating an east‐west axis for activities to relieve the present north‐south axis.

This would form the core of transport strategy. Capital intensive rail projects will face severe shortage of funds. An additional road/rail link has also been suggested to the mainland. The congestion in Bombay can be relieved if the master plan is prepared for an integrated system. Traffic and town planning must go hand in hand with priority to traffic planning.     

High-Speed Rail Operations on an Existing Network: An Assessment Model for China

High-speed rail operations have the potential to reduce the long-term decline in rail passenger travel demand for the medium to long distance inter-urban markets. Such decline has been evident through most of the industrialized countries where air and road transport tend to be the dominant modes. In China, the operations of long distance high-speed rail on fully dedicated track is not very easy to implement, due to the high proportion of passengers who travel between high-speed and conventional railways. An alternative approach would be to allow for mixed operations with trains of various speeds on the same track. This article puts forward a simulation model designed to allow an evaluation of the most efficient distance for high-speed rail operations under mixed train speed scenarios. The model takes into account the main operating parameters such as passenger volumes, train speeds, capital and maintenance costs, train operating costs and energy consumption. The distance of high-speed train running on conventional rail that will yield the most economic benefit can be estimated using the model. The article includes the results of using the model for a specific example. It is concluded that large-scale high-speed trains have the potential to be successfully operated on conventional rail networks.     

Attitudes of bus operators towards real-time transit information tools

Although it is apparent that providing useful information has a positive effect on transit riders, no studies to date have investigated bus operators’ reactions to real-time arrival information and other potential rider information tools. In this study, the project team surveyed 253 bus operators to determine their views and values concerning the existing use of real-time information and to ask about future transit rider information applications. Almost all operators (93 and 91 % on two separate questions) were positive or neutral to the provision of real-time information. In addition, operators were receptive to building other new information applications, with all applications in the survey being supported by at least 60 % of the bus operators. The two most widely supported potential applications in the survey were additional tools to help blind and deaf-blind riders (89 % of bus operators favored) and an application that would aid riders in identifying physical stop, shelter and bus issues such as graffiti, broken parts or a need for lights (88 % of bus operators). Applications displaying data about past performance or current bus capacity received the least support (66 and 61 % respectively). This research gives a better understanding of the impact of rider information tools on bus operators, including the views and values of the operators, and the harms and benefits of such tools.     

Mechanisms for the control of transnational shipping corporations

The author presents a model of the conflicts that arise in the transnational shipping industry with special emphasis on control alternatives during entry into shipping operations. He concludes that, since transnational shipping is a non-zero sum game, gains can be created for world shipping as a whole.     

Experimental validation of a mathematical model of a reed-valve reciprocating air compressor from an automotive-braking system

Mathematical simulation is the process of designing a model of a real system and then conducting experiments with the simulation to understand the system’s behavior. Mathematical simulation is widely used for investigating and designing compressors, and with a minimal number of simplifying assumptions, mathematical models can be used in conjunction with modern computing tools to solve complicated problems. A considerable amount of previous research has focused on the mathematical modeling of reciprocating air compressors used in automotive braking. The aim of the present work was to experimentally validate the mathematical model for such compressors. We present a simplified and effective mathematical model for estimating compressor performance, and this model can easily be executed using personal computers. Parameters such as compressor speed, discharge pressure and clearance volume were evaluated in terms of their effect on the thermodynamic behavior of compressors. The model can predict cylinder pressure, cylinder volume, cylinder temperature, valve lift and resultant torque at different crank angles; it can also predict the free air delivered and the indicated power of the compressor. Therefore, the model has been validated using experimental results.     

Statistical characterization of surfaces of corroded steel plates

The statistical characteristics of corroded steel plate surfaces exposed to marine environments are of interest for assessing longer term structural safety and integrity using probabilistic methods. This requires information about the variability of corrosion loss and pitting over surfaces. The present paper reports on the observed statistical character of the surfaces of 10 large (1.2 m × 0.8 m × 3 mm thick) steel plates exposed in temperate climate marine immersion, tidal and splash zones for 2.5 years. For the analysis the plates were cut into smaller segments that were mechanically scanned to obtain digitised surface topographies. These were then analysed to estimate the correlation structure and the standard deviation of the surface topography. Considerable differences were found for these and for the mean corrosion loss between different exposure zones. For any one segment the surface topography was found to be highly statistically dependent, implying that smaller coupon sizes can provide adequate estimates of corrosion loss. From this it may be inferred that the deepest pits are not statistically independent as commonly assumed in extreme value statistical representations.