Search results

1 – 10 of over 8000
Article
Publication date: 6 July 2012

Vahed Ghiasi, Samad Ghiasi and Arun Prasad

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…

Abstract

Purpose

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.

Design/methodology/approach

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.

Findings

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.

Originality/value

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?

Details

Journal of Engineering, Design and Technology, vol. 10 no. 2
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 1 January 1931

E.F. A.R.C.Sc.,F.R.Ae.S. Relf

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…

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 3 no. 1
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 February 1931

Ernest F. Relf

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…

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 3 no. 2
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 April 1955

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…

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 27 no. 4
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 September 1939

F.L. Wattendorf

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…

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 11 no. 9
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 March 1998

M.J.P. William‐Louis and C. Tournier

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…

Abstract

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.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 8 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 November 1965

D.R. Newman

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

Abstract

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.

Details

Aircraft Engineering and Aerospace Technology, vol. 37 no. 11
Type: Research Article
ISSN: 0002-2667

Open Access
Article
Publication date: 23 May 2022

Xiaofang Ma, Wenming Wang, Gaoguang Zhou and Jun Chen

This study aims to take advantage of the unprecedented anti-corruption campaign launched in China in December 2012 and examine the effect of improved public governance on…

Abstract

Purpose

This study aims to take advantage of the unprecedented anti-corruption campaign launched in China in December 2012 and examine the effect of improved public governance on tunneling.

Design/methodology/approach

This study uses a sample of Shanghai and Shenzhen Stock Exchange listed companies from 2010 to 2014 and conduct regression analyses to investigate the effect of improved public governance attributed to the anti-corruption campaign on tunneling.

Findings

This study finds that the level of tunneling decreased significantly after the anti-corruption campaign, suggesting that increased public governance effectively curbs tunneling. Cross-sectional results show that this mitigating effect is more pronounced for non-SOE firms, especially non-SOE firms with political connections, firms audited by non-Big 8 auditors, firms with a large divergence between control rights and cash flow rights and firms located in areas with lower marketization.

Practical implications

This study highlights the importance of anti-corruption initiatives in improving public governance and in turn reducing tunneling. This study provides important implications for many other emerging economies to improve public governance.

Originality/value

This study contributes to the literature on the role of public governance in constraining corporate agency problems and advances the understanding of the economic consequences of China's anti-corruption campaign in the context of tunneling.

Details

China Accounting and Finance Review, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1029-807X

Keywords

Article
Publication date: 19 April 2022

Fei Sun and Changjun Li

In order to improve the comprehensive evaluation level of shield tunnel structure health, taking a subway tunnel section as an example, and combined with the onsite…

Abstract

Purpose

In order to improve the comprehensive evaluation level of shield tunnel structure health, taking a subway tunnel section as an example, and combined with the onsite measured data, such as regular inspection, health monitoring and disease remediation, this paper introduces the variable weight theory to improve the traditional fixed-weight evaluation method from structural deformation, current durability and disease status.

Design/methodology/approach

Considering the influence of the fluctuation of each index value on the index weight, a comprehensive structural health evaluation model of shield tunnel based on an improved variable weight matter-element extension model is proposed.

Findings

Compared with the traditional fixed-weight evaluation method, this model can correct the evaluation distortion caused by the fluctuation of index value and has optimal effect.

Originality/value

The sensitive analysis shows that several key indicators of the main threats to tunnel structure are obtained to improve the efficiency of operation, maintenance and management of shield tunnel structure.

Details

International Journal of Structural Integrity, vol. 13 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

Open Access
Article
Publication date: 2 May 2022

Ao Li, Dingli Zhang, Zhenyu Sun, Jun Huang and Fei Dong

The microseismic monitoring technique has great advantages on identifying the location, extent and the mechanism of damage process occurring in rock mass. This study aims…

Abstract

Purpose

The microseismic monitoring technique has great advantages on identifying the location, extent and the mechanism of damage process occurring in rock mass. This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.

Design/methodology/approach

In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway. An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.

Findings

Microseismic events can be divided into high density area, medium density area and low density area according to the density distribution of microseismic events. The positions where the cumulative distribution frequencies of microseismic events are 60 and 80% are identified as the boundaries between high and medium density areas and between medium and low density areas, respectively. The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock, which is affected by the grade of surrounding rock and the span of tunnel. The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters. The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock. The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed. Based on the depth of high excavation damage zone of surrounding rock, the prestressed anchor cable (rod) is designed, and the safety of anchor cable (rod) design parameters is verified by the deformation results of surrounding rock.

Originality/value

The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable (rod).

Details

Railway Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2755-0907

Keywords

1 – 10 of over 8000