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This study aims to propose a series of numerical and surrogate models to investigate the aerodynamic pressure inside cracks in high-speed railway tunnel linings and to predict the stress intensity factors (SIFs) at the crack tip.

A computational fluid dynamics (CFD) model is used to calculate the aerodynamic pressure exerted on two cracked surfaces. The simulation uses the viscous unsteady κ-ε turbulence model. Using this CFD model, the spatial and temporal distribution of aerodynamic pressure inside longitudinal, oblique and circumferential cracks are analyzed. The mechanism behind the pressure variation in tunnel lining cracks is revealed by the air density field. Furthermore, a response surface model (RSM) is proposed to predict the maximum SIF at the crack tip of circumferential cracks and analyze its influential parameters.

The initial compression wave amplifies and oscillates in cracks in tunnel linings, resulting from an increase in air density at the crack front. The maximum pressure in the circumferential crack is 2.27 and 1.76 times higher than that in the longitudinal and oblique cracks, respectively. The RSM accurately predicts the SIF at the crack tip of circumferential cracks. The SIF at the crack tip is most affected by variations in train velocities, followed by the depth and length of the cracks.

The mechanism behind the variation of aerodynamic pressure in tunnel lining cracks is revealed. In addition, a reliable surrogate model is proposed to predict the mechanical response of the crack tip under aerodynamic pressures.

ON Friday, March 24, 1961, the Minister of Aviation, Mr Peter Thorneyeroft, officially opened a new high supersonic speed wind tunnel at the Royal Aircraft Establishment, Bedford. This tunnel provides the final stage in the present plans for expansion of the wind tunnel facilities at Bedford, being capable of providing speeds from Mach 2.5 up to Mach 5 in a working section measuring 4x3 ft. Three other tunnels arc already in operation at Bedford—these being the 13x9 ft. working section low‐speed tunnel, the 3x3 ft. tunnel, which is transonic and supersonic to Mach 2, and the 8x8 ft. tunnel, which is subsonic and supersonic to Mach 2.8.

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.

The cracking of a reinforced concrete lining has a significant influence on the safety and leakage of pressure tunnels. This study aims to develop, validate and apply a numerical algorithm to simulate the lining cracking process during the water-filling period of pressure tunnels.

Cracks are preset in all lining elements, and the Mohr−Coulomb criterion with a tension cutoff is used in determining whether a preset crack becomes a real crack. The effects of several important factors such as the water pressure on crack surfaces (WPCS) and the heterogeneity of the lining tensile strength are also considered simultaneously.

The crack number and width increase gradually with the increase in internal water pressure. However, when the pressure reaches a threshold value, the increase in crack width becomes ambiguous. After the lining cracks, the lining displacement distribution is discontinuous and steel bar stress is not uniform. The measured stress of the steel bar is greatly determined by the position of the stress gauge. The WPCS has a significant influence on the lining cracking mechanism and should not be neglected.

A reliable algorithm for simulating the lining cracking process is presented by which the crack number and width can be determined directly. The numerical results provide an insight into the development law of lining cracks and show that the WPCS significantly affects the cracking mechanism.

This paper aims to analyze the bearing characteristics of the high speed train window glass under aerodynamic load effects.

In order to obtain the dynamic strain response of passenger compartment window glass during high-speed train crossing the tunnel, taking the passenger compartment window glass of the CRH3 high speed train on Wuhan–Guangzhou High Speed Railway as the research object, this study tests the strain dynamic response and maximum principal stress of the high speed train passing through the tunnel entrance and exit, the tunnel and tunnel groups as well as trains meeting in the tunnel at an average speed of 300 km·h-1.

The results show that while crossing the tunnel, the passenger compartment window glass of high speed train is subjected to the alternating action of positive and negative air pressures, which shows the typical mechanic characteristics of the alternating fatigue stress of positive-negative transient strain. The maximum principal stress of passenger compartment window glass for high speed train caused by tunnel aerodynamic effects does not exceed 5 MPa, and the maximum value occurs at the corresponding time of crossing the tunnel groups. The high speed train window glass bears medium and low strain rates under the action of tunnel aerodynamic effects, while the maximum strain rate occurs at the meeting moment when the window glass meets the train head approaching from the opposite side in the tunnel. The shear modulus of laminated glass PVB film that makes up high speed train window glass is sensitive to the temperature and action time. The dynamically equivalent thickness and stiffness of the laminated glass and the dynamic bearing capacity of the window glass decrease with the increase of the action time under tunnel aerodynamic pressure. Thus, the influence of the loading action time and fatigue under tunnel aerodynamic effects on the glass strength should be considered in the design for the bearing performance of high speed train window glass.

The research results provide data support for the analysis of mechanical characteristics, damage mechanism, strength design and structural optimization of high speed train glass.

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 shield tunnels closely constructed near the foundations have an inevitable influence on the structures, even results in the large settlement or uplift of the structures.

The comparison of structural deformation of three different foundations is presented based on the field monitoring data.

Shield tunnelling parameters vary for the different types of foundations. For the long pile foundations, the recommended speed is 3 to 4 cm/min, the grouting pressure is about 0.3 MPa and the grouting rate ranges from 150 to 180.

The study based on the field monitoring data is rarely reported, especially the topic about the structural deformation of different types of the foundations.

THE general arrangement of the wind tunnel shown in Figs. 1 and 3 does not differ materially from the tunnels built up to the present on the plans of Professor Prandtl in Germany, England, America. It is an open jet tunnel with single return flow and two large elliptic nozzles of different design. A single stage helicoidal fan in the return flow provides the air stream. The fan is driven by a synchronous motor across an oil gear, Thoma‐Waldrich type, consisting of two pumps and a motor.

The purpose of this paper is to introduce the numerical methods in tunnel engineering and their capabilities to indicate the fracture and failure in all kinds of tunneling methods such as New Austrian Tunneling Method, tunnel boring machine and cut‐cover. An essential definition of numerical modeling of tunnels to determine the interaction between geo‐material (soil and rock) surrounding the tunnel structure is discussed.

Tunnel geo‐material (soil and rock) interaction requires advanced constitutive models for the numerical simulation of linear, nonlinear, time‐dependent, anisotropic, isotropic, homogenous and nonhomogeneous behaviors. The numerical models discussed in this paper are developed in finite element method (FEM), finite deference method (FDM), boundary element method and discrete element method and these tools are used to illustrate the behavior of tunnel structure deformation under different loads and in complicated conditions. The disadvantage of this method is the tunnel lining assumed an independent structure under fixed load which is unable to model soil‐lining interaction. Predicting the effect of all natural factors on tunnels is the most difficult method. The above‐mentioned numerical methods are very simple and quick to use and the results are conservative and practical for users. One of the most significant advantages of the numerical method is in predicting the critical area surrounding the tunnel and the tunnel structure before making the tunnel construction due to different loads.

Numerical modeling is used as control method in reducing the risk of tunnel construction failures. Since some factors such as settlement and deformation are not completely predictable in rock and soil surrounding the tunnel, using numerical modeling is a very economical and capable method in predicting the behavior of tunnel structures in various complicated conditions of loading. Another benefit of using numerical simulation is in the colorful illustrations predicting the tunnel behavior before, during and after construction and operation.

There are not many conducted studies using numerical models to tunnel structures that estimate the critical zones. As some of the methods available have limitation in simulating and modeling the whole tunnel design factors, numerical modeling seems to be the best option, because it is fast, economical, accurate and more interesting in predicating critical zones in tunnel. However, what softwares predict are not always the same as real ground nature conditions in which there is tunnel.

The purpose of this paper is to develop and present a hybrid design and fabrication method based on rapid prototyping (RP) and electrochemical deposition (ED) techniques to fabricate a pressure wind‐tunnel model with complex internal structure and sufficient mechanical strength.

After offsetting inward by applied coating thickness, the airfoil model was modified with three pairs of deflecting control surfaces and 24 surface pressure taps and internal passages. The stereolithography (SL) prototype components were fabricated on SL apparatus and roughened by chemical treatments. And then metal‐coated SL components of the airfoil model were created by ED technique. After assembling, a hybrid pressure airfoil model was obtained.

Electrodeposited nickel coating has dramatically improved the overall strength and stiffness of SL parts and the hybrid fabrication method is suitable to construct the wind‐tunnel model with complex internal structure and sufficient mechanical strength, stiffness.

Interface adhesion of SL‐coating is poor even if chemical roughening is applied and the further research is needed.

This method enhances the versatility of using RP in the fabrication of functional models, especially when complex structure with sufficient mechanical properties is considered. Although this paper took an airfoil wind‐tunnel model as an example, it is capable of fabricating other functional components with other rapid prototyping techniques such as FDM, SLS and LOM.