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The purpose of this study is to evaluate the methods employed for classifying and quantifying the potential of squeezing in tunnels. Along with the empirical and…
The purpose of this study is to evaluate the methods employed for classifying and quantifying the potential of squeezing in tunnels. Along with the empirical and semi‐empirical approaches presently available in order to anticipate the potential of squeezing tunnel problems, the squeezing potential of Karaj water transfer tunnel and North West Tunnel Convey (NWTC) tunnels (Lot 2), located in Iran, are evaluated and presented. Those two case studies have an interesting geology profile and parameters to identify and then evaluate the squeezing potential.
In recent years, there has been an increasing interest in the tunnel construction. This paper describes the squeezing behavior of poor rock mass associated with deformability and strength properties. In Karaj water transfer tunnel, there are eight lithological rock types; and NWTC tunnel (Lot2) has 21 Lithological rock types. The parameters for rock classification, such as rock quality designation (RQD), rock mass rating (RMR), modified RMR, Q‐system, geological strength index (GSI), rock mass index (RMi), and rock structure rating (RSR) are evaluated and presented here. The parameters mentioned above are the input parameters for squeezing study in Karaj and NWTC tunnels. According to different methods of squeezing evaluation of tunnel presented in tables, the results of two case studies are presented in this paper.
One of the more significant findings to emerge from this study showed that about 3 km of the second part of NWTC tunnel, and 2 km of the Karaj tunnel have high squeezing potential. This research deals with not only an overview of the methods used for the identifying and quantifying of squeezing along with the empirical and semi‐empirical approaches presently available in order to anticipate the potential of squeezing tunnel problem, but also the case studies of NWTC and Karaj tunnels to evaluate and compare the potential of squeezing by different methods. These two tunnel case studies have high potential of squeezing therefore the lining of those two tunnels must be strong enough to overcome this issue.
This study is a precise and concise comparison of the evaluation of tunnels under squeezing rock condition. The present study confirms the previous findings and contributes additional evidence that suggests that there are many studies conducted using empirical and analytical methods to determine the squeezing phenomenon in tunnels. This paper responds to the various questions like, what is the squeezing phenomenon. How can we quantify the potential of squeezing in weak rock? What are the different approaches to the understanding of squeezing phenomenon?
THE demand for aerodynamic research continues to grow, and there is difficulty in meeting it with the available equipment. The Compressed Air Tunnel will become available…
THE demand for aerodynamic research continues to grow, and there is difficulty in meeting it with the available equipment. The Compressed Air Tunnel will become available shortly, but will not very greatly alter the situation, as it will have a scries of scale‐effect problems of its own to solve, problems that have of necessity been shelved in the past, owing to the absence of any effective weapon of attack. The recent study of the design of open‐jet tunnels in this country has led to the realisation of the fact that a room which can contain a 7‐ft. tunnel of the N.P.L. type can quite easily house two open‐jet return‐flow tunnels of the same size or even slightly larger. A proposal has been made to increase very considerably the available tunnel equipment by replacing the 7‐ft. No. 1 tunnel at the Laboratory by two high‐speed open‐jet tunnels. In view of the feeling that some such step will be necessary in the near future unless research is to suffer delay, model tests have been made to provide design data so that the project could be rapidly carried into effect at short notice. There has been practically no expansion of wind‐tunnel equipment in this country since the War until the construction of the Compressed‐Air Tunnel was sanctioned and later the construction of a 24‐ft tunnel at Farnborough. While special tunnels such as these are absolutely necessary for the effective solution of certain problems, there is always a vast amount of research to be carried out in normal‐sized atmospheric tunnels of reasonable speed, and an extension of equipment on the lines suggested would undoubtedly be well worth the cost.
DURING the last year or two the construction of several new wind tunnels in this Country has been commenced, after many years of inactivity in this direction. The new…
DURING the last year or two the construction of several new wind tunnels in this Country has been commenced, after many years of inactivity in this direction. The new tunnels are intended either to bring existing equipment up‐to‐date or to meet specific needs for researches which cannot be satisfactorily carried out in the older tunnels. In all cases the new tunnels are of types very different from those previously in use in this country, and it is interesting to trace the reasons for the change. In order to do this it would be well to review the history of the development of the existing tunnel equipment, in order to understand in the first place why the standard type of wind tunnel used in this country was entirely different from, and in some respects less efficient than, that developed on the Continent. When the study of aerodynamic problems was undertaken at the National Physical Laboratory in 1909, the question of a suitable design of wind tunnel was naturally one of the first to be raised.
THE Press was recently given the opportunity of seeing some of the more modern aerodynamic research facilities of the Ministry of Supply at R.A.E. Farnborough and N.A.E…
THE Press was recently given the opportunity of seeing some of the more modern aerodynamic research facilities of the Ministry of Supply at R.A.E. Farnborough and N.A.E. Bedford. The Bedford establishment is administratively part of the R.A.E., and is concerned at present primarily with aerodynamic research on high‐speed aircraft. Later, work on engines will also be done there. It lies on the borders of three wartime R.A.F. airfields, the original intention being to build a runway which would enable jet aircraft to take off and land again within its length. The establishment has grown up from nothing since the war, and this is reflected in the attractive and orderly disposition of the buildings, their pleasing contemporary architecture, and the general impression of clean design. The site is still in the hands of the contractors, but it can be seen that when it is complete it will be a fine example of what such an establishment should look like. Credit for this must be shared between the Ministry of Supply, the Ministry of Works, and the contractors, who have allowed imagination to play its part in design, without it leading to extravagance. Particularly attractive are the colour schemes in the main administrative block, and the use of colour on the engineering plant itself.
THE Tsing Hua 15‐ft. wind tunnel, with interchangeable 18‐ft. section for full scale engine and airscrew tests, was recently erected in Central China. It was planned as…
THE Tsing Hua 15‐ft. wind tunnel, with interchangeable 18‐ft. section for full scale engine and airscrew tests, was recently erected in Central China. It was planned as the central organ for aerodynamic research in China and, as such, was subject to interesting design conditions. The main features of the tunnel design, as well as the considerations underlying their choice, are described in this article.
Describes the propagation of pressure waves when a train passes through a plain tunnel or tunnel equipped with side branches. A non‐homentropic one‐dimensional model is…
Describes the propagation of pressure waves when a train passes through a plain tunnel or tunnel equipped with side branches. A non‐homentropic one‐dimensional model is used to predict the flow generated. This model takes into consideration the train and tunnel geometry, the wall friction and heat transfer. The numerical calculation is performed using the classical method of characteristics. Near the train and tunnel ends, or at the junctions with the side branches, the flow is three dimensional. In the one‐dimensional theory, boundary conditions are applied to model the flows across these regions. The model used is validated by comparisons with experimental results. The use of airshafts to attenuate pressure waves is discussed.
An Outline of the Wind Tunnel Facilities available at Hatfield and a Description of the New Multi‐Fan Non‐Return Circuit V/S.T.O.L. Wind Tunnel. THE wind tunnel…
An Outline of the Wind Tunnel Facilities available at Hatfield and a Description of the New Multi‐Fan Non‐Return Circuit V/S.T.O.L. Wind Tunnel. THE wind tunnel establishment at Hatfield dates back to 1954, when the 2 ft. by 2 ft. high speed tunnel and the 9 ft. by 7 ft. low speed tunnel were commissioned.
The paper aims to predict longitudinal deformation of a tunnel caused by grouting under the tunnel bottom in advance according to the grouting parameters, which can ensure…
The paper aims to predict longitudinal deformation of a tunnel caused by grouting under the tunnel bottom in advance according to the grouting parameters, which can ensure the safety of the tunnel structure during the grouting process and also help to design the grouting parameters.
The paper adopted the analytical approach for calculating the longitudinal deformation of a shield tunnel caused by grouting under a tunnel, including usage of the Mindlin’s solution, the minimum potential energy principle and case validation.
The paper provides a variational method for calculating the longitudinal deformation of a shield tunnel in soft soil caused by grouting under the tunnel, which has high computational efficiency and accuracy.
This paper fulfils an identified need to study how the longitudinal deformation of a shield tunnel in soft soil caused by grouting under the tunnel can be calculated.
The purpose of this paper is to propose a new approach of using additively manufactured parametric models in the wind tunnel test-based aerodynamic shape optimization…
The purpose of this paper is to propose a new approach of using additively manufactured parametric models in the wind tunnel test-based aerodynamic shape optimization (ASO) framework and to present its applicability test results obtained from a realistic aircraft design problem.
For aircraft shape optimization, the following three methodologies were used. First, as a validation study, the possibility of using rapid prototyping (RP) model in the wind tunnel test was verified. Second, through the wind tunnel test-based ASO, the application and feasibility of the real fighter aircraft shape optimization were verified. A generic fighter configuration is parameterized to generate various test models using additive manufacturing. Wind tunnel tests are conducted to measure their stability criteria in high angle of attack (AOA). Finally, a computational fluid dynamics (CFD) study was performed and analysis procedures, costs and results compared to the wind tunnel test were compared and reviewed.
RP technology can significantly reduce the time and cost of generating parametric wind tunnel models and can open up new possibilities for wind tunnel tests to be used in the rigorous aerodynamic design loop. There was a slight difference between the results of the RP model and the metallic model because of rigidity and surface roughness. However, the tendency of the aerodynamic characteristics was very similarly predictable. Although there are limitations to obtaining precise aerodynamic data, it is a suitable method to be applied to comparative studies on various shapes with large geo-metric changes in the early phase of design. The CFD analysis indicates that the wind tunnel-based ASO using the RP model shows the efficiency corresponding to the CFD shape optimization.
The RP parametric models may have various assembly error sources and rigidity problems. The proposed methodology may not be suitable for collecting the accurate aerodynamic database of a final design; rather, the methodology is more suitable to screen out many configurations having fairly large shape variation in the early stage of the design process.
The wind tunnel test-based ASO can replace or supplement CFD-based ASO. In areas where CFD accuracy is low, such as high AOA flight characteristics, RP model wind tunnel-based ASO can be a research method that can secure both efficiency and accuracy advantages, providing ten times more effective in terms of cost and time. The wind tunnel test is used to obtain aerodynamic data at the final stage of shape design. It can be extended to a comparative study of several shapes in the early design phase. This procedure can be applied for both industrial level and educational aircraft design activities.
This study is the application to be applied as a parametric study on the whole aircraft, rather than using the RP model applying a simple partial control surface or configuration change of a part of the wing. The possibility of using the RP model was confirmed by comparing and verifying each other in a medium-sized wind tunnel using a relatively large RP model and a metallic model. It was verified that it can be applied in the shape design process, not the shape verification in the traditional design procedure, and a comparison with the CFD method was also performed. With further development and validation efforts, the new design framework may become an industrial standard for future aircraft development.
Purpose – This study explores the probability of expropriation of minority shareholders by controlling shareholders in the form of CEO compensation under an imperfect…
Purpose – This study explores the probability of expropriation of minority shareholders by controlling shareholders in the form of CEO compensation under an imperfect governance institution by using a novel Chinese dataset over 2001–2010.
Design/methodology/approach – We use a direct method to gauge controlling shareholders’ tunneling and expropriation of minority shareholders, and we present a simple model to link corporate governance and the degree of entrenchment by the largest shareholder. We use both Logit and Probit models to predict the likelihood of tunneling and use two-stage least square (2SLS) regression to address the endogeneity issues.
Findings – There are significant deterioration effects between controlling shareholder's tunneling and firm performance. Firms with more tunneling activities typically have larger controlling ownership, greater evidence of state control, less balance of power among large shareholders, and weaker board characteristics.
Research limitations/implications – The positive relationship between controlling shareholders’ tunneling and executive compensation implies that the controlling shareholder might divert personal benefits from the public firms at the expense of minority shareholders.
Originality/value – We focus on the effects of corporate governance restructuring on executive compensation and controlling shareholders’ tunneling in the Chinese context, and we also investigate whether these effects are stronger with the involvement of state ownership. We empirically address the issues between executive compensation and expropriation of minority shareholders.