2,308 research outputs found
Lining Technology of Saturated Sand Layer Underground Diversion Tunnel and the Measurement of Concrete Lining Thickness
No full textIn order to improve the construction technology quality of the diversion tunnel lining in saturated sand stratum, the lining technology of underground diversion tunnel in saturated sand stratum is studied in detail in this paper. Steel trolley is used to complete binding production, and HBT-20 concrete pump is used to transport concrete. Concrete construction starts from bottom plate and side arch. After the construction, the quality of the diversion tunnel lining is tested nondestructively by the impact elastic wave, and the thickness and defects of the lining are analyzed by the reflection characteristics and spectral relationship of the impact elastic wave. The strength of lining concrete is measured by the propagation characteristics of R wave and the relationship between wave velocity and strength. The results show that the maximum additional bending strain of tunnel wall is about 300 με. At measuring point B7, the thickness and strength of concrete lining can be accurately measured by nondestructive quality testing technology.In order to improve the construction technology quality of the diversion tunnel lining in saturated sand stratum, the lining technology of underground diversion tunnel in saturated sand stratum is studied in detail in this paper. Steel trolley is used to complete binding production, and HBT-20 concrete pump is used to transport concrete. Concrete construction starts from bottom plate and side arch. After the construction, the quality of the diversion tunnel lining is tested nondestructively by the impact elastic wave, and the thickness and defects of the lining are analyzed by the reflection characteristics and spectral relationship of the impact elastic wave. The strength of lining concrete is measured by the propagation characteristics of R wave and the relationship between wave velocity and strength. The results show that the maximum additional bending strain of tunnel wall is about 300 με. At measuring point B7, the thickness and strength of concrete lining can be accurately measured by nondestructive quality testing technology
Lining of the induction furnaces
No full textThis work deals with lining of electric induction furnaces. The first part describes the preparation of lining, its function during the running of furnace and also its tearing down at the end of work process. In the thesis is also discussed the use of rammed crucibles. The materials used for lining and rammed crucibles are described also in the sense of their chemical properties in connection with the possibilities of their use under different conditions. The practical part of the thesis describes the process of lining the electric induction furnace, which was realized by the author under the supervision of the supervisor
Reliability analysis of a steel fibre reinforced concrete tunnel lining
No full textAt the moment, there are no Dutch regulations giving criteria for the design of bored tunnels. These regulations are necessary to prove that the required safety and serviceability are guaranteed by the proposed design. The scope of the study presented in this report consists of a reliability analysis of a SFRC tunnel lining. This consists of the definition of the load and resistance factors that are considered necessary to make a design of a SFRC lining and the calculation of the failure probability of the tunnel in the ultimate limit state. The study carried out in this report is based on the ITM tunnel design case with a lining thickness of 0,40 m and a radius of 4,70 m. The tunnel lining can fail by several mechanisms. The mechanism that is examined in this study, consists of the failure of the tunnel lining under strain of the soil stresses in the ultimate limit state. The analysis is executed with a level II probabilistic design method. The basis of this method is that the parameters used in the structural design are not specified constants, but stochastic variables. The most advanced method of this level is the so-called Approximate Full Distribution Approach (AFDA). This method is used for the reliability analysis executed in this report. First of all, the reliability of the tunnel design is approached with a linear calculation model, i.e. with the analytical Duddeck model. The most remarkable conclusion drawn from the linear reliability analysis, is that the safety requirements are on the whole better met in case of more flexible and thinner inings. As this conclusion does not meet the expectations and as the use of a (simple) linear model has a real benefit, the impact of non-linear effects on the cross-section forces is examined in order to determine whether the assumption of linearity is likely to be acceptable within the limitations of the non-linear tunnel analysis. An important conclusion drawn from the non-linear reliability analysis is that the safety decreases with decreasing lining thickness. The latter refutes the conclusion drawn at the linear reliability analysis that the safety increases with decreasing lining thickness. Moreover, from the non-linear reliability analysis follows that it is not safe to use the (linear) analytical Duddeck method for the design of slender constructions. In general, it can be concluded that the examination of the safety of a tunnel lining is very extensive and that still a lot of work is left to be done.Hydraulic EngineeringCivil Engineering and Geoscience
Mechanical Behavior of Tunnel Lining with Cracks at Different Positions
No full textCracks in the lining significantly reduce the safety of a tunnel during operation. It is urgent to figure out the influence of cracks on tunnel carrying capacity. In this paper, three-dimensional model tests were conducted to investigate deformation, internal force, and deterioration laws of the lining with prefabricated cracks at different positions. The main conclusions were obtained as follows: (1) The carrying capacity of the lining structure with prefabricated cracks was reduced, and the deformation of the lining structure increased. The penetration of the vault crown crack accelerated the damage of the lining structure, and structural failure occurred when the crack went through at the left arch spring. (2) The internal force of the lining was greatly affected by the positions of prefabricated cracks. The internal forces of the lining structure decreased with the existence of prefabricated cracks. Whether or not there were prefabricated cracks, tension cracks appeared in the inside fiber of the vault and inverted arch. (3) The deformation of the lining structure with the existence of prefabricated cracks increased. When the prefabricated crack was located at the vault, the deformation was the largest, followed by the arch spring, side wall, and arch shoulder. (4) The analysis shows that prefabricated cracks at the vault are the most damaging under stress and deformation of the lining structure, so longitudinal cracks at the vault should be strengthened
Study on Crack Development of Concrete Lining with Insufficient Lining Thickness Based on CZM Method
No full textThe most common structural defect of a tunnel in the operation period is the cracking of concrete lining. The insufficient thickness of tunnel lining is one of the main reasons for its cracking. This study studied the cracking behavior of standard concrete specimens and the failure behavior of tunnel structures caused by insufficient lining thickness using Cohesive Zone Model (CZM). Firstly, zero-thickness cohesive elements were globally inserted between solid elements of the standard concrete specimen model, and the crack development process of different concrete grades was compared. On this basis, a three-dimensional numerical model of the tunnel in the operation period was established. The mechanism and characteristics of crack propagation under different lining thicknesses were discussed. In addition, the statistics of cracks were made to discuss the development rules of lining cracks quantitatively. The results show that the CZM can reasonably simulate the fracture behavior of concrete. With the increase in concrete strength grade, the number of cohesive damaged elements and crack area increases. The insufficient lining thickness changes the lining stress distribution characteristics, reduces the lining structure’s overall safety, and leads to the cracking of the diseased area more easily. When surrounding rock does not contact the insufficient lining thickness, its influence on the structure is more evident than when surrounding rock fills the entire lining thickness. The number of cohesive damaged elements and the size of the crack area increases significantly
Bored Tunnel Lining Behaviour in Discontinuous Rock: Railway Tunnel in Middle-East
No full textIn a bored railway tunnel project in the Middle-East, difficulties in terms of ovalization, water leakages and settlement of several lining rings located in a fault zone were observed at the end of the construction stage. The present research attempted to find the cause for this lining behaviour. The determination of critical loading conditions, the application of the longitudinal beam model and the analytical and numerical modelling (in Plaxis) of a monolith tunnel lining in abrupt ground property transition were analyzed. Thereby, the global lining stiffness reduction due to joints was also considered. The literature review led to the following expected factors that caused difficulties in the Middle-East case: the squeezing and submerged ground conditions, the rock mass disturbance and the improper backfilling of the rings. Additionally, the ring stiffness reduction due to joints was an essential factor for lining behaviour. The geotechnical conditions, the lining design and the observed difficulties in the case were defined in the next section. Critical missing information, such as geotechnical properties of the fault zone material and limited monitoring data, led to essential assumptions. The settlements were expected to be caused by rock mass disturbance and improper backfilling. These altered the water flow during and after the boring operations and led to lowering of the groundwater level and increase of effective stresses. The water leakages were caused by ring ovalization in the soft fault zone, leading to opening of joints. The analysis for this research was divided in 2D transversal, 2D longitudinal and 3D modelling of the lining in and around the fault zone. The 3D model was seen as the integral model, which took into account the transversal and longitudinal behaviour of the lining. However, most of the behaviour of the lining was analyzed by carrying out parametric analysis for both directions in 2D. Moreover, the 2D models were used to validate the results of the 3D model to identify the influence of the third dimension. The assessment of the results from these analyses led to the following conclusions. The behaviour of the tunnel lining in small width fault zones was governed by the transversal action. The ovalization was mainly influenced by the ground stiffness, the vertical to horizontal stress ratio, the backfilling stiffness and the ring stiffness. Using Erdmann's analytical solution, the approximate lining forces can be determined. However, this overestimated the ground pressures acting on the lining, especially in cases where vertical to horizontal stress ratios were not equal to 0.5. This was because the 2D transversal behaviour did not take into account the longitudinal arching effect, which depended mostly on the stiffness ratio between ground types. The final conclusion was that the global reduction of lining stiffness due to the joints led to a discrepancy with regard to the distribution of the longitudinal displacements. A complementary analysis using a numerical model taking into account the joint structure and discontinuous behaviour between rings would probably allow a better prediction of longitudinal displacements.Geotechnical Engineerin
A bifurcated circular waveguide problem
No full textThis is a pre-copy-editing, author-produced PDF of an article accepted for publication in IMA Journal of Applied Mathematics following peer review. The definitive publisher-authenticated version A D Rawlins. A bifurcated circular waveguide problem. J.I.M.A. 54 (1995) 59-81. Oxford University press is available online at: http://imamat.oxfordjournals.org/cgi/reprint/54/1/59.pdfA rigorous and exact solution is obtained for the problem of the radiation of sound from a semi-infinite rigid duct inserted axially into a larger acoustically lined tube of infinite length. The solution to this problem is obtained by the Wiener-Hopf technique. The transmission and reflection coefficients, when the fundamental mode propagates in the semi-infinite tube, are obtained. The present results could be of use for exhaust design, and as a possible instrument for impedance measurement
The Influence of Loading, Temperature and Relative Humidity on Adhesives for Canvas Lining
No full textThe structural conservation of canvas paintings may require lining, a process in which a secondary canvas is adhered to the reverse of the damaged original canvas to provide additional support. Choosing the optimum adhesive or canvas for lining is challenging. Comprehensive data on thermal and mechanical behaviour of different adhesives to enable the conservator to make informed choices for their treatment purposes is scarce. Hence, in this study, four prevalently used adhesives for lining are chosen and their thermal and mechanical behaviour, such as the glass transition and melting temperatures, static lap shear strength and creep resistance, are compared. Thermal properties of the different adhesives are characterised using differential scanning calorimetry (DSC). Furthermore, the effect of temperature cycles (25, 35, and 45°C at a fixed relative humidity of 48%) on the creep behaviour of lined canvases is evaluated. Lap shear and creep experiments are performed on lined canvas mock-ups. The four adhesives tested are: studio formulations of an animal glue-wheat flour paste, as well as a beeswax-damar resin mixture; a patented formula based on an ethylene vinyl acetate copolymer mixture (BEVA 371 O.F.™); and a mixture of two industrially produced acrylic copolymers (Plextol™ D541 and K360). The results demonstrate the remarkable effect of temperature on the creep behaviour of lined canvases, which can be related to their thermal stability.Structural Integrity & CompositesAdhesion Institut
Seismic Behaviour of Shallow Tunnelling Method Tunnels Accounting for Primary Lining Effects
No full textThe shallow tunnelling method (STM) is usually used to construct shallow tunnels buried in soft ground. It consists of primary lining and secondary lining (tunnel). In the seismic design of STM tunnels, it is usually assumed that the secondary lining (tunnel) is resistant to all seismic effects. However, the soil–primary–secondary lining system may generate complex interaction phenomena during ground shaking. Compared with the case where the primary lining is not considered, the existence of the primary lining alters the seismic response of the secondary lining (tunnel). The paper attempts to investigate this complex interaction, focusing on the response of the secondary lining (tunnel). The full dynamic time history analysis is adopted to investigate the interaction in the transversal direction. A case history of the Hohhot (China) arched STM tunnel buried in a stratified soil deposit has been analyzed. Two tunnel configurations for a two-dimensional plane strain model of STM tunnels in Hohhot are studied and compared, including a model with primary lining and one without primary lining. A numerical parametric analysis was conducted to elucidate critical response characteristics of STM tunnels. Salient parameters that may affect the dynamic response of the tunnel were studied, including the characteristics of ground motion, the characteristics of contact interface, the characteristics of the soil, and the characteristics of the tunnel lining. The response characteristics of the tunnel are compared and discussed, including horizontal acceleration, deformation mode, lining internal force, and lining damage. The results show that the primary lining has a significant influence on the magnitude and distribution of the seismic response, especially considering the nonlinearity of the soil and the nonlinear characteristics of the tunnel lining. The effect of primary lining on the seismic response is about 5–35%
Tunnel lining detection and retrofitting
No full textThe underground tunnel structure is important and common in transport infrastructures. With the increasing service time, it is crucial to detect the deteriorations in the ageing tunnel linings and make informed retrofitting decisions to ensure their structural safety and extend their service life cycle. This emphasizes the importance of understanding the framework of tunnel lining detection, evaluation, and retrofitting. However, there is no up-to-date review available that covers the entire workflow of tunnel lining detection and retrofitting. This paper provides a comprehensive review of non-destructive testing (NDT) methods, health evaluation methods, and retrofitting methods for tunnel linings. The achievements, challenges, and development trends of these methods are illustrated. Specifically, NDT methods for three representative tunnel lining defects, including cracks, leakage, and voids, are introduced and analyzed to show the corresponding advantages and disadvantages. Based on the data obtained by the defect detection methods, the procedures for lining health status evaluation are also summarized to provide a systematic and quantitative evaluation of tunnel linings. Finally, the retrofitting methods and techniques that are suitable for lining structures are reviewed. This paper provides an insight into the development of structural health monitoring (SHM) and the maintenance of tunnel linings, offering a systematic guide for understanding the framework of tunnel lining detection and retrofitting
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