scholarly journals 3D Numerical Investigation of Ground Settlements Induced by Construction of Istanbul Twin Metro Tunnels with Special Focus on Tunnel Spacing

2019 ◽  
Author(s):  
Behnaz Hallaji Dibavar ◽  
Mohammad Hossein Ahmadi ◽  
Seyed Morteza Davarpanah
Keyword(s):  
Urban Areas ◽  
Longitudinal Direction ◽  
Numerical Approach ◽  
Surface Settlement ◽  
Special Focus ◽  
Direction Parallel ◽  
Tunnel Diameter ◽  
Twin Tunnels ◽  
Good Agreement ◽  
Ground Settlements

One of the most important considerations of tunneling in urban areas is controlling the amount of surface settlement that occurs during construction stages. The goal of this paper is to investigate the effect of spacing of Istanbul Twin Metro Tunnels on the surface settlement excavated by NATM method in YENIKAPI-UNKAPANI metro line. For this purpose, the focus has been placed on the effect of longitudinal and transversal spacing between tunnels supported by an umbrella arch protecting method. (FLAC3D) was implemented to simulate the excavation sequence. According to the analysis, the amount of settlement by numerical approach was about 23.5 mm which was in good agreement with the field monitoring results that was 26.5 mm. Moreover, the interaction between twin tunnels by the increase in spacing between twin tunnels in the direction perpendicular to tunnel axis decreases and becomes less effective at the location about 3 times of the tunnel diameter. Similarly, the interaction between twin tunnels in the direction parallel to tunnel axis decreases as the spacing increases. In other words, by increasing the distance between tunnel faces in longitudinal direction at a distance about 3 times of the tunnel diameter, there is still interaction between tunnels and it doesn’t disappear completely. Therefore, it is recommended to keep this distance at about more than 2.5 times of tunnel diameter so that settlement can stay within acceptable range.

Deceleration of sliding motorcycles (mainly scooters) in accident reconstructions

2017 ◽  
Vol 232 (7) ◽  
pp. 866-876 ◽  
Author(s):  
Carlo Cialdai ◽  
Dario Vangi ◽  
Antonio Virga
Keyword(s):  
Urban Areas ◽  
Test Session ◽  
Road Accidents ◽  
Factors Affecting ◽  
Different Types ◽  
Energy Dissipated ◽  
Comparison Of The Results ◽  
Two Wheeler ◽  
The Impact ◽  
Good Agreement

This paper presents an analysis of the situation in which a two-wheeler (i.e. a motorcycle, where the term motorcycles includes scooters) falls over to the side and then successively slides; this typically occurs in road accidents involving this type of vehicle. Knowing the deceleration rate of the sliding phase allows the kinetic energy dissipated and the speed of the motorcycle just before the fall to the ground to be calculated. These parameters are very important in the analysis and reconstruction of accidents. The work presented in this paper was developed in two experimental test sessions on fully faired motorcycles which are mainly of the scooter type and widely used in urban areas. In the first session, sliding tests were carried out, with the speed in the range 10–50 km/h, on three different types of road surface. Analysis of the evidence allowed the dissipative main phases of motion of the motorcycle (the impact with the ground, the rebounds and the stabilized swiping) to be identified and some factors affecting the phenomenon to be studied. The coefficient of average deceleration was calculated using two typical equations. The second test session consisted of drag tests. In these tests, the motorcycle, which had previously laid on its side, was dragged for a few metres at a constant speed of about 20 km/h, while the drag force was measured. A comparison of the results obtained in these tests with those obtained in the sliding tests yielded very good agreement in the coefficients of deceleration.

Investigation of Recirculating Casing Treatment for Low-Pressure Ratio Mixed-Flow Micro-Compressor

2020 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Pressure Ratio ◽  
Numerical Approach ◽  
Efficiency Loss ◽  
Stall Margin ◽  
Design Point ◽  
Casing Treatment ◽  
Final Design ◽  
Upstream Flow ◽  
Total Pressure Ratio ◽  
Good Agreement

Abstract This paper investigates the recirculating casing treatment (RCT) of a low total pressure ratio micro-compressor to achieve stall margin enhancement while minimizing the design point efficiency penalty. Three RCT injection and extraction configurations are studied, including combined slot-duct, ducts only, and slot only. The numerical approach is validated with a tested micro-compressor using RCT. A very good agreement is achieved between the predicted speedlines and the measured results. To minimize the design point efficiency loss, it is observed that the optimal location of extraction and injection is where the recirculated flow rate can be minimized at the design point. To maximize stall margin, extraction location should favor minimizing the tip blockage such as at the location where the tip flow separation of the baseline blade is fully developed. In addition, the slot configuration that generates pre-swirl to the upstream flow is beneficial to improve stall margin due to reduced incidence. The highest stall margin enhancement achieved is 9.49% with the slot geometry that has the extraction at the 62%C chordwise location, but has a design point efficiency loss of 1.9%. Overall, a small efficiency penalty of 0.6% at the design point is achieved for the final design with the stall margin increased by 6.2%.

scholarly journals Tolerance to Human Presence, a Comparison between Rural and Urban Birds in Southeastern Brazil

2021 ◽  
Vol 2 (3) ◽  
pp. 1-4
Author(s):  
Maria Cecília Barbosa de Toledo
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Bird Species ◽  
Urban Environments ◽  
Southeastern Brazil ◽  
Special Focus ◽  
Forest Fragments ◽  
Urban Birds ◽  
Human Presence ◽  
Individual Bird

Green urban areas such as parks, squares, gardens, and forest fragments present a large diversity of uses and conservation objectives. These spaces provide resources for many species of birds that are confronted with the necessity of living in proximity to humans. It is assumed that bird species that acquire resources in urban environments live in a constant state of fear to guarantee survival and reproduction. In this context, the objective of this study was to evaluate the tolerance of birds with respect to human presence in two distinct conditions, rural areas (low level of human presence) and urban areas (high level of human presence). The fieldwork was conducted in a city in the Southeast region of Brazil, and the methodology used the alert distance and flight initiation measurements based on the approach of an observer to the individual bird being focused. Our results suggest that individuals observed in urban areas rely on shorter alert and escape distances, especially males, adults, and birds that forage in interspecific flocks. We discuss the challenges and strategies with respect to escape characteristics of urban birds, with special focus on the economic escape theory. In general, our results support those from studies conducted in other urban areas in different biogeographic regions, and they will aid in comprehending the impacts caused by the increase in urban areas around the world.

scholarly journals Analysis of Total Column CO<sub>2</sub> and CH<sub>4</sub> Measurements in Berlin with WRF-GHG

2019 ◽  
Author(s):  
Xinxu Zhao ◽  
Julia Marshall ◽  
Stephan Hachinger ◽  
Christoph Gerbig ◽  
Jia Chen
Keyword(s):  
Urban Areas ◽  
Initial Conditions ◽  
Ghg Emissions ◽  
Concentration Field ◽  
Weather Research And Forecasting ◽  
Background Concentration ◽  
Wind Fields ◽  
Simulated Wind ◽  
Global Population ◽  
Good Agreement

Abstract. Though they cover less than 3 % of the global land area, urban areas are responsible for over 70 % of the global greenhouse gas (GHG) emissions and contain 55 % of the global population. A quantitative tracking of GHG emissions in urban areas is therefore of great importance, with the aim of accurately assessing the amount of emissions and identifying the emission sources. The Weather Research and Forecasting model (WRF) coupled with GHG modules (WRF-GHG) developed for mesoscale atmospheric GHG transport, can predict column-averaged abundances of CO2 and CH4 (XCO2 and XCH4). In this study, we use WRF-GHG to model the Berlin area at a high spatial resolution of 1 km. The simulated wind and concentration fields were compared with the measurements from a campaign performed around Berlin in 2014 (Hase et al., 2015). The measured and simulated wind fields mostly demonstrate good agreement and the simulated XCO2 agrees well with the measurement. In contrast, a bias in the simulated XCH4 of around 2.7 % is found, caused by relatively high initialization values for the background concentration field. We find that an analysis using differential column methodology (DCM) works well for the XCH4 comparison, as corresponding background biases then cancel out. From the tracer analysis, we find that the enhancement of XCH4 is highly dependent on human activities. The XCO2 signal in the vicinity of Berlin is dominated by anthropogenic behavior rather than biogenic activities. We conclude that DCM is an effective method for comparing models to observations independently of biases caused, e.g., by initial conditions. It allows us to use our high resolution WRF-GHG model to detect and understand sources of GHG emissions quantitatively in urban areas.

LONG-TERM MECHANICAL COMPATIBILITY OF POLYPROPYLENE SURGICAL MESHES

2019 ◽  
Vol 19 (06) ◽  
pp. 1950056
Author(s):  
MIGLENA KIRILOVA-DONEVA ◽  
DESSISLAVA PASHKOULEVA
Keyword(s):  
Abdominal Wall ◽  
Elastic Properties ◽  
Longitudinal Direction ◽  
Tensile Tests ◽  
Direction Parallel ◽  
Inguinal Area ◽  
Surgical Meshes ◽  
Mechanical Compatibility

The properties of meshes: Surgimesh®, Technomesh[Formula: see text] and SurgiproTM aged for up to four years were assessed using tensile tests. We discovered that the elasticity of Technomesh[Formula: see text] increased in both directions, Surgimesh[Formula: see text] became more elastic in the longitudinal direction while the elastic properties of SurgiproTM remained unchanged. The mesh samples did not significantly change their strength and deformability with age. Samples from umbilical and inguinal area of the abdominal wall were isolated from 14 donors. The investigation included 90 specimens divided into three age subgroups — A (up to 60 years), B (61–80 years) and C (over 80 years). The long-term mechanical compatibility of human fascia and meshes was compared. The elastic properties of the meshes are closer to the elastic properties of the fascia in the direction parallel to fibers if the donors’ age is up to 60 years.

scholarly journals New Governance of Urban Areas in France

2016 ◽  
Vol 16 (3) ◽  
pp. 479-496
Author(s):  
Michæle Breuillard
Keyword(s):  
Local Government ◽  
Urban Areas ◽  
Local Governments ◽  
Urban Governance ◽  
Modern Society ◽  
Special Focus ◽  
New Governance ◽  
Perfect Model ◽  
Institutional Architecture ◽  
Turf Wars

The paper analyses urban governance and decentralisation in France. It explains the “quiet revolution” that wants to set the legal base of French local government back to the drawing board with special focus on the reform of local government in urban areas. The context of the too many too small communes – at the heart of the reform programme – is described since it is a typically French evil (part 2). In the absence of any successful top-down policy of amalgamating communes, new communes are deemed to be the effective solution along with a new mapping of intercommunal joint bodies (part 3). Finally, the paper describes what the metropolis “à la française” consists of (part 4) with a special focus on Lyon – the perfect model for the whole country – and Paris and Aix-Marseille as the worst pupils in transition. France stands out as an important case where new powers bestowed upon metropolitan governments have curbed the jurisdictions of regional governments. The ambiguity over the powers and functions of local governments triggers obdurate turf wars between the two levels of government, which clearly indicates that the governance of any modern society needs to be simplified. If left unaddressed, competition – not coordination or cooperation – between regionalization and metropolitanisation, regionalization and local governments, governability and multilevel governance is likely to become the norm. The author concludes that France desperately needs an in-depth reform of its institutional architecture, which is regularly postponed. What is required is a simplification of governmental machinery: more efficiency in local policies, a clearer allocation of responsibilities, reduced expenses, and governance closer to citizens.

Surface settlement during shield tunnelling at CH218 in Taipei

1998 ◽  
Vol 35 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Chang-Yu Ou ◽  
Richard N Hwang ◽  
Wei-Jung Lai
Keyword(s):  
Ground Surface ◽  
Earth Pressure ◽  
Surface Settlement ◽  
Pressure Balance ◽  
Transit System ◽  
Ground Surface Settlement ◽  
Earth Pressure Balance Shield ◽  
Shield Tunnelling ◽  
Earth Pressure Balance ◽  
Twin Tunnels

This paper presents the surface settlement performance induced by the foamed type of earth pressure balance shield in contract CH218 of the Hsintien Line of the Taipei Rapid Transit System. The surface settlement characteristics caused by the single tunnel and by twin tunnels with reference to two sections spaced at 87 m are studied. Field observations indicate that the surface settlement trough due to the single tunnel can be represented by the normal distribution. The distance of the inflection point to the tunnel center and maximum surface settlement value are consistent with those found in the literature. The characteristics of the surface settlement trough are related to the type of the soil, particularly where the crown of the tunnel is located in a layered soil deposit. The ground surface settlement induced by twin tunnels was found to be larger than estimated using the principle of superposition.Key words: shield tunnelling, surface settlement, field observation.

Numerical Simulation of Broadband Combustion Noise With the RPM-CN Approach

2009 ◽  
Author(s):  
B. Mu¨hlbauer ◽  
R. Ewert ◽  
O. Kornow ◽  
B. Noll ◽  
M. Aigner
Keyword(s):  
High Efficiency ◽  
Numerical Approach ◽  
Combustion Noise ◽  
Acoustic Measurements ◽  
Noise Sources ◽  
Computational Costs ◽  
Acoustic Perturbation ◽  
Simulation Results ◽  
The Time Domain ◽  
Good Agreement

A new numerical approach called RPM-CN approach is applied to predict broadband combustion noise. This highly efficient hybrid CFD/CAA approach can rely on a reactive RANS simulation. The RPM method is used to reconstruct stochastic broadband combustion noise sources in the time domain based on statistical turbulence quantities. Subsequently, the propagation of the combustion noise is computed by solving the acoustic perturbation equations (APE-4). The accuracy of the RPM-CN approach will be demonstrated by a good agreement of the simulation results with acoustic measurements of the DLR-A flame. The high efficiency and therefore low computational costs enable the usage of this numerical approach in the design process.

scholarly journals Time-lapse gravity and levelling surveys reveal mass loss and ongoing subsidence in the urban subrosion-prone area of Bad Frankenhausen, Germany

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 599-619 ◽  
Author(s):  
Martin Kobe ◽  
Gerald Gabriel ◽  
Adelheid Weise ◽  
Detlef Vogel
Keyword(s):  
Mass Loss ◽  
Soil Water ◽  
High Precision ◽  
Urban Areas ◽  
Quantitative Estimation ◽  
Monitoring Network ◽  
Time Lapse ◽  
Ground Subsidence ◽  
Special Focus ◽  
Precision Time

Abstract. We present results of sophisticated, high-precision time-lapse gravity monitoring that was conducted over 4 years in Bad Frankenhausen (Germany). To our knowledge, this is the first successful attempt to monitor subrosion-induced mass changes in urban areas with repeated gravimetry. The method provides an approach to estimate the mass of dissolved rocks in the subsurface. Subrosion, i.e. leaching and transfer of soluble rocks, occurs worldwide. Mainly in urban areas, any resulting ground subsidence can cause severe damage, especially if catastrophic events, i.e. collapse sinkholes, occur. Monitoring strategies typically make use of established geodetic methods, such as levelling, and therefore focus on the associated deformation processes. In this study, we combine levelling and highly precise time-lapse gravity observations. Our investigation area is the urban area of Bad Frankenhausen in central Germany, which is prone to subrosion, as many subsidence and sinkhole features on the surface reveal. The city and the surrounding areas are underlain by soluble Permian deposits, which are continuously dissolved by meteoric water and groundwater in a strongly fractured environment. Between 2014 and 2018, a total of 17 high-precision time-lapse gravimetry and 18 levelling campaigns were carried out in quarterly intervals within a local monitoring network. This network covers historical sinkhole areas but also areas that are considered to be stable. Our results reveal ongoing subsidence of up to 30.4 mm a−1 locally, with distinct spatiotemporal variations. Furthermore, we observe a significant time-variable gravity decrease on the order of 8 µGal over 4 years at several measurement points. In the processing workflow, after the application of all required corrections and least squares adjustment to our gravity observations, a significant effect of varying soil water content on the adjusted gravity differences was figured out. Therefore, we place special focus on the correlation of these observations and the correction of the adjusted gravity differences for soil water variations using the Global Land Data Assimilation System (GLDAS) Noah model to separate these effects from subrosion-induced gravity changes. Our investigations demonstrate the feasibility of high-precision time-lapse gravity monitoring in urban areas for sinkhole investigations. Although the observed rates of gravity decrease of 1–2 µGal a−1 are small, we suggest that it is significantly associated with subterranean mass loss due to subrosion processes. We discuss limitations and implications of our approach, as well as give a first quantitative estimation of mass transfer at different depths and for different densities of dissolved rocks.

scholarly journals The role of H<sub>2</sub>SO<sub>4</sub>-NH<sub>3</sub> anion clusters in ion-induced aerosol nucleation mechanisms in the boreal forest

2018 ◽  
Vol 18 (17) ◽  
pp. 13231-13243 ◽  
Author(s):  
Chao Yan ◽  
Lubna Dada ◽  
Clémence Rose ◽  
Tuija Jokinen ◽  
Wei Nie ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Atmospheric Aerosols ◽  
Organic Molecules ◽  
Special Focus ◽  
Anion Clusters ◽  
Nucleation Mechanisms ◽  
Important Pathway ◽  
Chamber Studies ◽  
Good Agreement

Abstract. New particle formation (NPF) provides a large source of atmospheric aerosols, which affect the climate and human health. In recent chamber studies, ion-induced nucleation (IIN) has been discovered as an important pathway of forming particles; however, atmospheric investigation remains incomplete. For this study, we investigated the air anion compositions in the boreal forest in southern Finland for three consecutive springs, with a special focus on H2SO4-NH3 anion clusters. We found that the ratio between the concentrations of highly oxygenated organic molecules (HOMs) and H2SO4 controlled the appearance of H2SO4-NH3 clusters (3<no.S<13): all such clusters were observed when [HOM] ∕ [H2SO4] was smaller than 30. The number of H2SO4 molecules in the largest observable cluster correlated with the probability of ion-induced nucleation (IIN) occurrence, which reached almost 100 % when the largest observable cluster contained six or more H2SO4 molecules. During selected cases when the time evolution of H2SO4-NH3 clusters could be tracked, the calculated ion growth rates exhibited good agreement across measurement methods and cluster (particle) sizes. In these cases, H2SO4-NH3 clusters alone could explain ion growth up to 3 nm (mobility diameter). IIN events also occurred in the absence of H2SO4-NH3, implying that other NPF mechanisms also prevail at this site, most likely involving HOMs. It seems that H2SO4 and HOMs both affect the occurrence of an IIN event, but their ratio ([HOMs] ∕ [H2SO4]) defines the primary mechanism of the event. Since that ratio is strongly influenced by solar radiation and temperature, the IIN mechanism ought to vary depending on conditions and seasons.

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