Australian private-vehicle fleet changes on register and on road, 1971–1982

Despite stagnation in new-vehicle sales from the mid 1970s, both the size and total usage made of the Australian stock of cars and station wagons continued to grow unabated into the early 1980s. Such apparently contradictory trends were an international phenomena, as were increased sourcing of vehicles from Japanese manufacturers, and the experience of less than favourable economic and demographic conditions. This paper looks at the factors behind the movements noted, and attempts to assess to what extent the “downsizing” phenomena observed overseas was encountered in Australia. Increasing vehicle life expectancy and an initially favourable age structure were found to account for contradictory growth rates in new registrations and the vehicle stock, while increased lifetime utilisation of light/medium vehicles accounted for much of the increase observed in total distance travelled. Only a weak downsizing trend was detected commencing circa 1979, its weakness reflecting an unexpected trend away from light vehicles. Projections indicate that if levels of, and size patterns associated with, new-vehicle registrations persist, downsizing trends will continue to be weak, and overall stock growth rates are likely to slow, although stagnation is unlikely by 1990.     

Study on State Parameter Control of Intake Air in Utility Tunnels Based on BB-MOPSO北大核心CSCD

In order to explore the control method of the intake air state in utility tunnels when the outside fresh air humidity is too high, taking the ventilation works of a utility tunnel section in Pingtan comprehensive experimental area as the research background, this paper proposes the control method of intake air state parameters for ventilation and dehumidification in utility tunnels under normal and accident conditions, by means of the effective ventilation and dehumidification duration prediction model, the evolutionary multi-objective algorithm (EMOA), and in combination with the ventilation control requirements. The results show that the intake air state parameter controller can be adjusted freely according to the different requirements of decision makers for ventilation fan working duration and dehumidifier working temperature and moisture content, and the optimized appropriate control objectives can be achieved, which is conducive to the real-time decision-making of the intake air state parameter control for ventilation and dehumidification in utility tunnels. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Distribution Laws of Earth Pressure Acting on a Shield Tunnel Based on Measured Data北大核心CSCD

The earth pressure acting on a shield tunnel is intrinsically related to synchronous grouting, the position of the shield machines, the rigidity of the segment and stratum, etc. Existing theoretical formulas and empirical methods couldn′t exactly reflect the actual state of the segment of a shield tunnel during construction due to the com⁃plexities mentioned above. Based on earth pressure data measured at 52 monitoring sections in 35 tunnels, the distri⁃bution laws and influential factors are analyzed. The results show that: 1) the earth pressure scope is 0 to 400 kPa for over 90% of the total samples, but is recommended to be 0.3 to 0.4 MPa for the empirical grouting pressure; 2)the earth pressure on the segment and the buried depth approximately have an exponential relationship, with the dif⁃ference between the max. earth pressure and the stable earth pressure decreasing with an increase of the buried depth; 3) the lateral pressure coefficient range is 0.5 to 2.3, which is partially out of the scope of recommended values(0.5 to 1.0) of surrounding rock of grade Ⅵ, so it is not appropriate to follow the recommended values in the specifi⁃cation; 4) the relationship of the earth pressure and the segment/soil stiffness ratio presents a quadratic function, and the most reasonable value for the stiffness ratio of the segment/soil is 1.0; and 5) there are four typical stages of the spatial distribution of earth pressure on a segment in clay stratum—the erection stage, the grouting influence stage,the consolidation contraction stage and the recovery stage, with the distribution of the circumferential earth pressure being asymmetrical. The distribution curves of the earth and water pressure in sand and soil layers are classified as a“weak decay pulse fluctuation”and“double hump,”respectively. After stabilizing, the circumferential earth pressure is notably in a symmetrical distribution, and the water pressure exhibits a light bulb shaped distribution (large at the lower part and small at the upper part). These conclusions provide a reference for studying the mechanism of earth pressure functions and perfecting the design of segments for shield tunnelling. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Some comments on origin–destination matrix estimation

Estimation of origin–destination (O–D) matrices from link count data is considered. This problem is challenging because the number of parameters to be estimated is typically larger than the number of network links. As a result, it is (usually) impossible to identify a unique optimal estimate of the O–D matrix from mean link traffic counts. However, information from the covariance matrix of link count data collected over a sequence of days can relieve this problem of indeterminacy. This fact is illustrated through a simple example. The use of second-order statistical properties of the data in O–D matrix estimation is then explored, and a class of estimators proposed. Practical problems of model mis-specification are discussed and some avenues for future research outlined.     

Study on Designed Water Pressure Limit on Secondary Lining for Single-Track Railway Tunnels with High Water Pressure北大核心CSCD

With the rapid development of China high speed railway, there is a dramatic increase of deep-buried and long mountain tunnels, and more and more tunnels are disturbed by high water pressure during construction and operation. Design for tunnel lining with high water pressure is one of the central concerns in the field of tunnel engi-neering, and the key problem is to forecast water pressure on the secondary lining and determination of water pressure resistance grade. The upper limit of water pressure on the secondary lining is studied by investigation and analysis in this paper. The study shows: (1) There should be an upper limit for the grade of water pressure resistance; (2) It is not very effective to improve the tunnel structure bearing capacity by only increasing the lining thickness haphazard-ly, and the appropriate maximum thickness of secondary lining is 1 m; (3) It is also unsatisfactory to improve the tunnel structure bearing capacity by simply increase concrete strength grade. The appropriate concrete grade is between C40 and C50. (4) In view of tunnel structure safety and good operation performance, the upper limit of water pressure resist grade should be no more than 1.2 MPa. When water pressure on the secondary exceeds the designed value,comprehensive measures should be taken to adjust the value to the appropriate range. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A Preliminary Study on the Law of Ground Settlement Caused by Shield Tunnelling Based on the Stratum Characteristic Value M S北大核心CSCD

Based on an analysis of monitoring data of surface settlement in the construction of a shield running tunnel of Beijing metro, an improved hyperbolic model was proposed to fit the ground subsidence law, and the characteris⁃ tic factor M S was used to evaluate the stratum under the condition of shield construction. The relationship between stratum parameters and surface settlement was studied, with the results indicate that the surface settlement caused by shield construction complies with hyperbolic distribution and it is basically stable at 30 days, the larger the value of M S is, the better the conditions of the stratum is and the smaller the settlement is; a certain correlation exists be⁃ tween the parameters of improved hyperbolic model and the characteristic value M S . © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

A Comment on ‘The Myth of Travel Time Saving’

Abstract

This paper reports on what appears to be the first attempt to map the perceived holistic dynamics at work in contemporary Brazilian railway development. The published perspectives of recognized experts in the Brazilian railway industry were mapped using the problem structuring methodology known as Strategic Options Development and Analysis (SODA). SODA is essentially a cognitive mapping approach and, in this case, it enabled a classification of the issues involved in railway development, as well as the detailed analysis of particular causes and effects acting upon the issues. Two particularly disturbing results are discussed in some length: the detrimental effects of the alleged misappropriations of public funds, and the identification of a degenerative feedback loop system at the heart of railway decision‐making. Overall, the paper shows that the situation faced by railway development in Brazil is constituted by a dynamic interaction of non‐independent problems, indicating the presence of a complex problem‐system requiring conceptual structure in a manner that permits analysis without ignoring systemic integrity. As such, the paper serves as a platform from which further use of SODA in this context might be considered as a decision support tool.     

Analysis on Gas Characteristics of the Sichuan Red-bed Section of ChengduGuiyang Railway and Suggestion on Division of Gas Working Areas in the Survey Stage北大核心CSCD

Combining with the borehole gas concentration tests for the Sichuan red-bed section of the Chengdu-Guiyang Railway, this paper analyzes its correlation with the stratum chronology geological structure, and tunnel depth on the basis of data statistics, and puts forward the suggestion to qualitatively and quantitatively divide gas working areas. The results show that the correlation between the tunnel gas concentration and the stratum chronology is not significant in the Sichuan red-bed section of the Chengdu-Guiyang Railway (except coal-bearing strata); geological structure plays a controlling role in gas transport and accumulation; and the positive correlation between the gas concentration and the tunnel depth is significant. According to the above conclusions, it could qualitatively divide the gas working areas according to the geological structure and mapping information collected during the survey stage, and quantitatively divide the gas working areas according to the gas concentration test results. The final categorization of gas working areas can be determined by combining the qualitative and quantitative results. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Passing Bays for Slow Moving Vehicles on Rural Two‐lane Roads

Abstract

Slow‐moving vehicles, including agricultural vehicles, on arterial highways can cause serious delays to other traffic as well as posing an extra safety risk. This paper elaborates on a small‐scale solution for these problems: the passing bay. It investigates the impacts of a passing bay on the total delay for other motorized vehicles, the number of passing manoeuvres and hindered vehicles, and the mean delay per hindered vehicle. The latter is also considered to be an indicator for traffic safety. The calculations are performed for two characteristic trips with a slow‐moving vehicle. The passing bay is an effective solution to reducing delays on arterial highways when two‐way hourly volumes exceed 600–1000 vehicles. The effects depend on the trip length and speed of the slow‐moving vehicle, and on the passing sight distance limitations of the road. A distance of 2–4?km between the passing bays seems an acceptable compromise between the reduction of delay for other motorized vehicles and the extra discomfort and delay for drivers of slow‐moving vehicles. This result also shows that passing bays are not effective in regions where slow‐moving vehicles mainly make trips shorter than this distance.     

Influence of Pit Foundation Excavation on an Adjacent Metro北大核心CSCD

With the development of urban metro systems, the influence of foundation pit construction on metro fa-cilities and related protection measures are getting more and more attention. A technical program for metro assess-ment at different phases of foundation pit construction is proposed using the statistics and analysis of a foundation pit of the Hangzhou metro. Qualitative and quantitative methods for analyzing the influence that foundation pit exca-vation has on metro systems are studied, and a series of protective measures suitable for foundation pit construction are summarized. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Recognition and tracking of spatial–temporal congested traffic patterns on freeways

The two models FOTO (Forecasting of Traffic Objects) and ASDA (Automatische Staudynamikanalyse: Automatic Tracking of Moving Traffic Jams) for the automatic recognition and tracking of congested spatial–temporal traffic flow patterns on freeways are presented. The models are based on a spatial–temporal traffic phase classification made in the three-phase traffic theory by Kerner. In this traffic theory, in congested traffic two different phases are distinguished: “wide moving jam” and “synchronized flow”. The model FOTO is devoted to the identification of traffic phases and to the tracking of synchronized flow. The model ASDA is devoted to the tracking of the propagation of moving jams. The general approach and the different extensions of the models FOTO and ASDA are explained in detail. It is stressed that the models FOTO and ASDA perform without any validation of model parameters in different environmental and traffic conditions. Results of the online application of the models FOTO and ASDA at the TCC (Traffic Control Center) of Hessen near Frankfurt (Germany) are presented and evaluated.     

Impacts of parental gender and attitudes on children’s school travel mode and parental chauffeuring behavior: results for California based on the 2009 National Household Travel Survey

Research has shown that parental attitudes are a significant predictor of children’s active commuting (walking or biking) to school. However, the impact of parental gender on parental attitudes, and the link between parental attitudes and the gender gap in parental chauffeuring behavior have not received much attention. This paper examines these questions by applying discrete choice models to California data from the 2009 National Household Travel Survey while controlling for a wide range of variables characterizing parents, their children, households, schools, and the local built environment. Our results, conveyed via odds ratios, show that mothers are more likely to have higher concerns about traffic volume, which in turn reduces the likelihood that their children will walk or bike to school. Moreover, even though parental attitudes significantly influence parental chauffeuring behavior, their ability to explain the gender chauffeuring gap is limited. When holding equal concerns, mothers are still more likely than fathers to chauffeur their children to school. Finally, while distance to school and several land use measures (e.g., population density, urbanization level, and percentage of renters) are statistically significant, the impact of an objective measure of walkability is quite small. These results suggest that interventions targeting an increase in children’s walking and biking to school should focus on the concerns of mothers, especially as they relate to traffic characteristics.     

Analysis on the Effects of Overloading on the Mechanical Properties of Tunnel Structures in the Silty Ground --A Case Study of Sutong River-crossing GIL Utility Tunnel北大核心CSCD

Based on the Sutong GIL utility tunnel project, which is constructed by the shield machine under the river, and as for the overloading problem at the river bank slope during operating period, the refined threedimensional finite element model was established to study the deformation and cracking characteristics of the tunnel segment structure under different forms of overloading. The evolution laws of section convergence, joint opening and structural stress were analyzed, and the structure damage mechanisms were revealed under conditions of large area loading and local loading. The surface-surcharge control standard was proposed. For the big diameter shield tunneling crossing the silty clay, the research results show that: (1) the deformation failure process is divided into three stages under large area loading condition, taking the design load and compressive yield of rebars inside haunch as the critical points respectively. The first stage is characterized by the elastic stress, the second stage is in plastic state with fracture, and the third stage is accelerating deformation and instability stage. The vertical convergence is 110.5 mm with no opening of joints when rebars are yielded; (2)the deformation failure process under local loading condition is also divided into elasticity, plasticity and instability stages, taking the design load and tensile yield of rebars outside haunch as the critical points respectively. The vertical convergence is 152.6 mm with joint opening of 4.36 mm; (3) the early-warning values of additional stress on the ground under conditions of large area loading and local loading are 110 kPa and 70 kPa respectively. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

The effects of a compressed working week on commuters’ daily activity patterns

This study was based on 220 randomly selected government employees of the University of the Philippines in Los Baños, and was carried out after the Philippine government implemented an experimental two-month compressed working week scheme. The study aimed to examine compressed working week-related lifestyle pattern changes, especially changes in activity–time patterns. The moderating effects of compressed working week to the commuters were also explored. Survey results showed that two-hour increases in the compressed working week workday substantially impacted activity–travel patterns. Commuters reduced household activities by about one hour, sleeping time by about 20 minutes, and pre-work preparation time by about 30 minutes. Commuting times also significantly declined during the compressed working week. This study also identified factors that moderated the compressed working week plan’s effects on activity–travel patterns.     

General Construction Technology Scheme of Tianshan Shengli Tunnel on Urumqi-Yuli Expressway北大核心CSCD

With a total length of about 22 km, Tianshan Shengli Tunnel on Urumqi-Yuli Expressway is currently the longest expressway tunnel under construction in the world. It adopts the construction scheme of "3 tunnels (2 D& B main tunnels and 1 TBM-driven middle pilot tunnel) + 4 shafts", which is characterized by great construction difficulty and high technical standard requirements. The tunnel construction is faced with technical challenges such as TBM passing through large fault fracture zones, long-distance construction ventilation in three tunnels, deep and large shaft construction and logistics organization in two-main tunnel construction assisted by middle pilot tunnel. In the parallel three-tunnel method design of Tianshan Shengli Tunnel, the TBM-driven middle pilot tunnel can not only play the role of advanced pilot tunnel, but also assist the construction of the two main tunnels and speed up the construction progress. For the middle pilot tunnel, the TBM excavation diameter is 8.4 m, and the initial support is designed as 100% force-bearing capacity in construction period, which can meet the requirements for two-way material transportation, ventilation and belt mucking in the pilot tunnel. Vault suspension scheme is adopted for the continuous belt conveyor, which can reduce the impact on the material flow organization in the cross passages. Multifunctional service vehicles (MSVs) independently developed by CCCC Group are used for the transportation of TBM materials and prefabricated inverted arch blocks, which can realize double-headed driving. TBM will pass through two large fault fracture zones F6 and F7. According to the stability of the surrounding rock at the tunnel face, the targeted treatment measures would be adopted. If necessary, the scheme of "steel segment + extruded concrete" shall be used for the initial support. In case of serious machine jamming or rock collapse, the heading expansion excavation method or bypass heading method shall be used. Tianshan Shengli Tunnel adopts phased forced ventilation option, and the ventilation mode is designed in stages with the change of tunnel construction stage. The fans and air pipes used are imported ones, and a ventilation management team is set up to strengthen ventilation management and ensure ventilation quality. Highly mechanized construction is used for the two D& B main tunnels, the application of equipment such as three-arm rock drilling jumbo and wet shotcrete machine is promoted, so as to reduce the number of workers and labor intensity, and improve work efficiency. The deep shafts of Tianshan Shengli Tunnel are constructed by short-section excavation and lining mixed operation method, and the initial support is lined by formwork pouring concrete, so as to realize safe and rapid excavation. According to the research results, the construction technology scheme for Tianshan Shengli Tunnel can meet the needs of tunnel construction. The research results can be directly used to guide the construction of Tianshan Shengli Tunnel, and provide reference for the construction of extra long highway tunnels in high-altitude areas. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

The influence of neighborhood types on active transport in China’s growing cities

Rapid urban expansion in China has created both opportunities and challenges for promoting active transport in urban residential communities. Previous studies have shown that the urban form at the city scale has affected active transport in Chinese cities. However, there is less agreement about how the physical and social variations of neighborhood types should be addressed. This research investigates the four most representative neighborhood types found in Chinese cities: traditional mixed-use, slab block work-unit, gated community, and resettlement housing. Household travel diaries conducted in Chengdu in 2016 were analyzed using binary logistic regressions, supplemented by informal onsite interviews. The findings indicate significant variations in the use and accessibility of active transport in each neighborhood type for non-work trips. This suggests that each neighborhood type may need different strategies for promoting active transport: (1) the traditional mixed-use neighborhoods are in need of intensified urban retrofitting projects to reclaim public open space; (2) the work-unit could benefit from comprehensive plans rather than a patchwork of projects; (3) while opening up gated communities can improve porosity across neighborhoods and promote active transport, the more pressing issue may be their inability to keep up with the transportation needs of the residents; and (4) residents of resettlement housing should have better access to employment using transit and non-motorized modes.     

Research on the Dust Removal Technology for Shield Tunnel Overhaul Construction北大核心CSCD

The shield tunnel is an ultra-long linear space. It will cause a lot of dust during the tunnel maintenance and overhaul operation, which is extremely unfavorable to the physical and mental health of the construction personnel and the environment outside the tunnel. It is difficult to guarantee the ventilation effect of the linear space using the conventional dust removal technology, which directly affects the construction safety and overhaul period. Therefore, based on the overhaul of a cross-river tunnel in Shanghai, combined with Computational Fluid Dynamics (CFD) simulation, device optimization and process combination, a three-stage dust reduction standardization process for tunnel overhaul construction is proposed, namely taking a water sprayer at the working point to control the dust at the source (primary protection); installing electrostatic dust removal and water filtration dust removal equipment in the tunnel(secondary protection); and installing two sets of water curtain spray device at the two tunnel exits to prevent dusts from diffusing into the atmosphere. It explores the actual dust-reducing effects of different dust-removing measures and layout combinations, laying a technical foundation for green and efficient dust reduction. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

Heat Release Rate and Temperature Field of a Bus on Fire北大核心CSCD

Bus fires are a common source of fires that occur in tunnels and are a huge threat to the safety of the tunnel structure and related personnel. An elaborate numerical simulation model of a bus is established considering the different combustion characteristics of the bus body, seats, decorations and baggage. For fires occuring at the bus head, middle part or back seat, the temperature field, heat release rate (HRR) and characteristics of the fire are ana-lyzed. The HRR calculation formula is obtained by superimposing a Boltzmann curve on a Gaussian curve. The re-sults show the peak and average values of a bus HRR are 48 MW and 8.1 MW, respectively, and the released energy due to combustion is 14.5 GJ; the maximum burning temperature reaches 1 040℃ and the temperature near the door can reach 60℃ after 120 sec. The temperature rises fastest at the bus door when the fire occurs at the rear of the bus and it has a high chance of detonating the fuel tank. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

“Comparing guideway transit implementation plans,including the impact on road traffic”

A methodology for comparing phased implementation plans for a new fixed guideway transit system in an urban area is presented. Four assumptions are made: (1) the guideway system replaces existing or planned bus service, (2) superior service on the new system results in increased ridership when compared to buses; (3) presence of the guideway facility redirects outward urban growth resulting in additional ridership, and (4) conversely, the absence of any action on the new guideway facility reinforces a diffuse urban growth pattern that creates an irreversible loss of transit ridership. The economic comparision of alternative plans includes total as well as “relative” inflation of principal cost components. A key feature of the proposed methodology is including in the comparisons the costs of private automobile mileage that could have been replaced by transit. These costs are expressed as “fuel” and “all other” automobile costs; favorable transit system implementation schedules can then be identified as a function of parametrically assumed values for these two unit costs. A hypothetical example demonstrates the proposed method.