Twin Tube Research Articles

Numerical analysis of rock fall at Hanekleiv road tunnel

The twin tube, 1,765 m long Hanekleiv road tunnel is located in Southeast Norway. Ten years after completion of the tunnel, a serious rock fall occurred in the southbound tube, approximately 1.1 km from the northern tunnel entrance, in a fault zone containing swelling clay. In addition to swelling, gravitational collapse due to the very low internal friction played an important role in the development of the instability. Numerical analysis has been carried out for the rock slide. Modelling based on the support actually applied indicated cracks during tunnel excavation as well as the tunnel collapse. Simulation showed that even reinforced shotcrete ribs or 25 cm thick concrete lining, based on the Q-system, may not be sufficient for the fault zone.

Computer Aided Valve Design of Shock Absorbers Used in Vehicles

The valve design of a rear twin tube shock absorber belongs to a light commercial vehicle whose damper characteristics already known has been realized by the help of a computer program called “Dr”, and compared with the actual application results. The program gives user results about the valve parts to get the right target characteristics. After obtaining the necessary parts’ results, the needed damping performance test has been performed by the shock absorber, which has been conflated according to the program. The actual results and target characteristics were compared. ”Dr” program enables the user to select the correct parts to be used in valve system by detecting every effect on target characteristics diagram. By comparing the overall effect of the parts selected, shock absorber valve system is conflated according to the valve components obtained from the computer program.

Surface settlement predictions for Istanbul Metro tunnels excavated by EPB-TBM

In this study, short-term surface settlements are predicted for twin tunnels, which are to be excavated in the chainage of 0 + 850 to 0 + 900 m between the Esenler and Kirazli stations of the Istanbul Metro line, which is 4 km in length. The total length of the excavation line is 21.2 km between Esenler and Basaksehir. Tunnels are excavated by employing two earth pressure balance (EPB) tunnel boring machines (TBMs) that have twin tubes of 6.5 m diameter and with 14 m distance from center to center. The TBM in the right tube follows about 100 m behind the other tube. Segmental lining of 1.4 m length is currently employed as the final support. Settlement predictions are performed with finite element method by using Plaxis finite element program. Excavation, ground support and face support steps in FEM analyses are simulated as applied in the field. Predictions are performed for a typical geological zone, which is considered as critical in terms of surface settlement. Geology in the study area is composed of fill, very stiff clay, dense sand, very dense sand and hard clay, respectively, starting from the surface. In addition to finite element modeling, the surface settlements are also predicted by using semi-theoretical (semi-empirical) and analytical methods. The results indicate that the FE model predicts well the short-term surface settlements for a given volume loss value. The results of semi-theoretical and analytical methods are found to be in good agreement with the FE model. The results of predictions are compared and verified by field measurements. It is suggested that grouting of the excavation void should be performed as fast as possible after excavation of a section as a precaution against surface settlements during excavation. Face pressure of the TBMs should be closely monitored and adjusted for different zones.

Environmental effects of tunnel excavation in soft and shallow ground with EPBM: the case of Istanbul

In metro tunnel excavations, it is important to control surface settlements observed before and after excavation, which may cause damage to surface structures. Otherwise, the metro tunnel cannot perform the task expected, and the advantages of the tunnel are lost. In this study, short-term surface settlements and their effect on buildings are examined in three zones for twin tunnels, which have been excavated between the Otogar and Kirazli 1 stations of the Istanbul Metro line, and are 5.8 km in length. Geology in the study area is composed of fill, stiff clay, dense sand, very dense sand, and hard clay, respectively, starting from the surface. Tunnels are excavated by using two Earth Pressure Balance Tunnel Boring Machines (EPBMs) with a 6.5 m diameter as twin tubes with 14 m distance from center to center. The EPBM in the right tube is followed about 100 m behind the other tube. Segmental lining with 1.4 m of length is currently employed as final support. The results of this study indicate that, with EPBM excavation method in shallow depths and soft grounds, the damage done to the environment prolonged project costs up to 15.8% more. In addition, tunnel conditions prolonged the project schedule to 29.3%.

Latest research and development of twin‐straight tube Coriolis mass flowmeters

PurposeThe paper aims to theoretically predict sensor signals and calibration factors for twin‐straight tube Coriolis flowmeters. It also aims to determine an optimal flow path to minimize pressure loss.Design/methodology/approachTwo major aspects involved in the latest research and development of a series of twin‐straight tube Coriolis mass flowmeters are presented. Firstly, the theoretical method adopted for the concept design to predict sensor signals and calibration factors is given. This is essentially a finite element method using the fluid structure interaction theory based on a Timoshenko beam coupled with one‐dimensional flow. Secondly, detailed design using computational fluid dynamics is described to optimise pressure loss. Finally, experimental results from testing a prototype meter are given and compared with the numerical results.FindingsFinds that sensor signals and calibration factors can be predicted with the presented method. Also finds that pressure loss can be minimized with an optimized flow splitter.Practical implicationsComparison between experiments and theoretical results shows agreement and indicates the effectiveness of computer‐aided engineering at an early development stage of Coriolis mass flow sensors.Originality/valueProvide a theoretical model to predict sensor signals and calibration factors for Coriolis mass flowmeters. Introduce an optimized splitter shape for a twin tube configuration.

Modelling a Twin Tube Cavitating Shock Absorber

An analytical method to quantify the damping force of a twin tube shock absorber is proposed. Fluid and chambers compressibility effects and fluid cavitation are included. A comparison of a calculated damping force against the ideal damping force (assuming that non-cavitation occurs) is presented.

Complications in Endoscopic Anterior Thoracolumbar Spinal Reconstructive Surgery

The use of endoscopic, minimally invasive surgical techniques in the reconstruction of the anterior column of the spine results in a significant decrease of approach-related complications. Depending on the level of injury, every stage of the surgical procedure is associated with a specific risk of complications requiring a detailed preparation of the operation. Preoperative preparations aim at recognition and improvement of preexisting cardiopulmonary diseases (e. g. chronic obstructive pulmonary diseases) as well as planning of anesthesia (twin tube airway, monitoring) and surgical technique, including optimal position of the patient, approach, reduction and stabilization of the fracture. Intraoperatively, a specific management is necessary to avoid complications, e. g. vascular, dura, or spinal cord injuries or lesions of the lung and the abdominal organs. In the postoperative course, general complications (infection, wound healing problems, bleeding, atelectasis), implant- associated complications (aseptic loosening, cage sinking), or fusion-associated complications (loss of reduction, pseudarthrosis, corresponding problems) have to be differentiated.

Construction of long and large twin tube tunnel in Korea–Sapaesan tunnel

The Sapaesan tunnel, the 4km twin tunnel with 4 lanes, is the longest 4-lane road tunnel in Korea. This tunnel is under construction with two years of delayed schedule because of the strong opposition of environmental and religious bodies. Therefore, maximizing the construction efficiency is demanded in tunnel project to compensate for delayed time. This paper introduces several advances in the construction of the Sapaesan tunnel by increasing tunnel cycle length, modifying excavation sequence and setting up concrete lining synchronized with excavation process. Also, TSP(Tunnel Seismic Prediction) survey was carried out to predict the geological condition of tunnel face ahead. With these continuous efforts, the construction period of the Sapaesan tunnel is expected to be shortened more than 10 months. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

Dublin Port Tunnel – excavation of an 11.8 m diameter urban motorway tunnel

Every year more than 2,000,000 heavy goods vehicles pass through Dublin Port. The vehicles contribute to serious traffic congestion in the city centre of Dublin. The Dublin Port Tunnel was planned to connect Dublin Port to the M1 Motorway in the north of the city and remove a predicted 9000 vehicles a day from the centre. The twin tube road tunnel will be approximately 4.5 km long with each tube having two lanes of carriageway. Sections of the tunnel at the north and south were constructed by cut and cover methods with the central 2.6 km of route being constructed by bored tunnelling methods. The central section passed under a large number of residential properties. The NMI Consortium was awarded the design and build contract in December 2000. The consortium consisted of Nishimatsu, Mowlem and Irishenco. Nishimatsu were responsible for the design and construction of all the civil works related to the bored tunnels. The geology along the tunnel alignment consisted of approximately 500 m of Dublin Boulder Clay with the remaining section in the Dublin Formation that comprised carboniferous limestone with inter bedded shales. The predicted geology, worksite availability, contract programme and environmental requirements led to the selection by Nishimatsu of two different 11.8 m diameter TBMs. A hard rock TBM excavated two 2.2 km drives mainly within the Dublin Formation. The second machine was an Open-Face type TBM equipped with two intermediate decks and three excavator arms and excavated two short 330 m drives in boulder clay. Both machines were refurbished and supplied by Herrenknecht. Both tunnels were lined with a structural concrete segmental primary lining and an in situ concrete secondary lining containing polypropylene fibres. The precast concrete linings consisted of six segments and a key. The lining utilised hydrophilic gaskets. A number of tests were conducted to demonstrate the designed cruciform joints could be adequately sealed. The secondary lining provided fire resistance to the primary lining and a smooth finish for painting, luminescence and cleaning. The contract specified a fire resistance period to a modified hydrocarbon fire curve and full-scale fire tests were carried out to demonstrate compliance at TNO in the Netherlands. The tunnels pass under a large number of residential properties. During tunnel construction ground borne vibration, regenerated noise and settlement would occur. Extensive predictions and assessments were undertaken in advance of construction. A research project was initiated on these aspects that continued as the construction work progressed. The settlement, vibration and noise were continually monitored reviewed and analysed. (A). Reprinted with permission from Elsevier. For the covering abstract see ITRD E124500.

Development of a back analysis algorithm using flac

The main focus of this study is vertical displacement monitoring and verification along with preliminary support design for the four geotechnical sectors of the twin tube Konak tunnel that was constructed in a highly populated area in İzmir. The displacements of the tunnel that were obtained through numerical analysis were verified by comparing them with the displacements obtained by construction monitoring. In the study area, volcanics, pyroclastics and some sedimentary deposits (sandstone, mudstone and conglomerate) often intertongue with each other especially in the exit portal area. The accurate estimation of the shear strength and deformation parameters of these units is important for the displacement predictions and for the assessment of tunnel stability. Rock mass classification systems, namely, RMR, Q system and GSI have been employed to obtain the rock mass shear strength and deformation parameters along with performing empirical tunnel support design. Numerical analysis has been performed by using the finite element analysis for assessing tunnel support design and for predicting the vertical displacements at five different measurement points around the tunnel periphery and in the four geotechnical sectors of the tunnel.An evaluation of the results revealed that about 70% of the predicted displacements matched the measured displacements while only about 12.5% of the displacement predictions exceeded the measured displacements by more than about 50%. Moreover, it was observed that neither the support system elements nor the rock mass have yielded due to the redistribution of the stresses imposed by the disturbance related with the tunnel excavation.

Roach habitat shifts and foraging modified by alarm substance 2. Reasons for different responses of fish in field and laboratory studies

The Schreckstoff-induced fright reaction (shift in fish depth distribution) was studied in roach from a European lowland lake in two twin vertical tubes of 0.85 m diameter and 11.5 m depth (Plon Plankton Towers) in an attempt to find possible reasons for the weakness of roach responses to the alarm substance in the field, as compared to those in laboratory conditions. Roach (fork length 15.4 ± 1.6 cm), fed Daphnia and chironomids under diel 9/15 h light/dark periodicity, displayed a transitory but firm response to the alarm-substance treatment in one of the towers, while no change was seen in the reference one. The mean depth of fish within 1 h of dusk following Daphnia supply to the towers' epilimnia (0-2.5 m depth), as well as 3 h later in the dark, was significantly greater in the treatment than in the reference tower. The response was more pronounced in prey (Daphnia) density than in the depth distribution of roach. The indirect effects on Daphnia were extremely strong (Daphnia many-fold more abundant in the tower with alarm substance than in the reference one), but shortlasting. Frightened fish were more reluctant to feed than the reference fish in the daylight, but the initial evening difference in Daphnia abundance vanished overnight due to feeding in the dark.

Tunnelling projects in Singapore: an overview

The introduction reviews the tunnelling carried out in Singapore since the early eighties. Between 1983 and 1990, Phases 1 and 2 of the mass rapid transit system were constructed. These included some 20 km of bored and cut and cover tunnels together with 18 underground stations. Some particular points of interest in this massive project are briefly commented upon. Reference is also made to other underground or underwater schemes undertaken during this period such as the proposed large caverns project and the submerged tunnel to Pulau Seraya. A description of the subsurface works, now under construction in Singapore, follows. This includes an all underground North-East railway line, 20 km long with 16 stations. At a budget of US$3 billion, this is a major civil engineering undertaking. Another project is the extension of the railway to Changi Airport which involves 3.5 km of twin tube tunnelling together with a major underground station which is fully integrated into the airport terminals. An ongoing programme of further major railway extensions over the next 10 to 15 years is in place and an outline is given of some of the most important underground sectors. Other proposed projects such as the underground roads system and the deep level sewers are briefly described. Together they demonstrate the very significant volume of underground construction scheduled for the next century in Singapore.

Extreme deformation and damage during the construction of large tunnels

Extreme deformations occurred during the construction both prior to and through a significant fault zone along the 16-m-wide. three-lane, twin tubes of the Bolu Mountain Tunnel of the 114 km Anatolian Motorway in north-central Turkey. Semi-concurrent excavation of the full top benches of both large tunnels was carried out through the fault zone with a final design deformation tolerance of 500mm in accordance with a NATM design philosophy. During excavation maximum deformations in the left and right tubes reached 580 mm and 350 mm, respectively. With continued semi-concurrent excavation through the fault zone an additional 140 mm of deformation occurred in the left tube thus, greatly exceeding the design tolerance. Extensive damage of the installed tunnel supports in the form of cracked shotcrete and distorted steel arches was observed in both tubes. An investigation was carried out on behalf of re-insurers to assess the causes of the additional deformation that exceeded the design tolerance. The main cause of the additional deformation aabove the design tolerance has been attributed to the re-start of excavation of the large lower benches of both tubes and the significant stress re-distribution that occurs with this excavation stage for large tunnels sited in weak geological conditions. This paper presents the summary findings of the review of the investigation that was carried out for re-insurers of the project as to the causes of the additional deformation that exceeded the design tolerance.

FLUID DAMPING CONTROLLED INSTABILITY OF TUBES IN CROSSFLOW

The mathematical model for fluid damping controlled instability of tubes in crossflow presented in this paper is based on unsteady flow theory. Motion-dependent fluid forces are measured in a water channel. From the measured fluid forces, fluid stiffness and fluid damping coefficients are calculated as a function of reduced flow velocity, oscillation amplitude, and Reynolds number. Once these coefficients are known, the mathematical model can be applied to predict structural instability due to fluid damping. The cases considered are a single tube, twin tubes, tube row, triangular array, and square arrays. The results show instability regions that are based on the fluid damping coefficients and provide answers to a series of questions on fluidelastic instability of tube arrays in crossflow.

STOREBAELT EASTERN RAILWAY TUNNEL: CONSTRUCTION.

Keywords AS STOREBAELTFORBINDELSEN, MT GROUP, MONBERG & THORSEN, DYCKERHOFF & WIDMANN, CAMPENON BERNARD, SOGEA, KIE TUNNELS, RAILWAYS, CONSTRUCTION, BORING, CROSS PASSAGES, HAND, MINING, METHODS, CUT AND COVER, CIVIL ENGINEERING, WORKS, GEOLOGY, WATER, PRESSURE, EARTH, BALANCE, MACHINES, MACHINERY, TBM, TUNNELLING, MODIFICATION, UNDERSEA, SUBMARINE, DEWATERING, CRYOGENICS, FREEZING, JUNCTIONING, GLACIAL, TILL, GROUND, TREATMENT, ONSITE, MANUFACTURING, HIGH, STRENGTH, DURABILITY, CONCRETE, LININGS, EPOXY, COVERED, COATED, REINFORCEMENT, CAGES, PROJECTS, MANAGEMENT, CONTRACTS, BORED, JOINT VENTURES, BEHAVIOUR, ALIGNMENT, SURVEYS, MUCK, DISPOSAL, SEABED, WATER, CON STOREBAELT, EASTERN DENMARK, SCANDINAVIA... Show All

Austrian road tunnel supported by water-expanded bolts : Muller, S Tunn TunnlgSummer 1991: NATM Special Issue, P13–14

Article describing the 4.3 km long twin tube Oswaldiberg road tunnel, currently the largest project of its kind in Austria. Completion of this tunnel is required in order to provide a bypass to relieve serious congestion in Villach caused by through-traffic. Provides details on the geology of the area, the drilling machinery used, and reinforcement methods.

Pool boiling heat transfer on finned tubes—an experimental and theoretical study

Pool boiling heat transfer of R11 is investigated experimentally and theoretically on single tubes and twin tube arrangements. Finned tubes with 19 and 26 fins per inch (fpi) are used. The refrigerant evaporates at a saturation state of 1 bar on the outside of the electrically heated tubes. For the twin tube arrangements the tube pitch is varied between, s/dF = 3.0 and 1.05. The heat transfer on the upper tube of the twin tubes is enhanced compared with the single tube, while the heat transfer on the lower tube is not affected by the upper tube. The maximum heat transfer of the upper tube increases with increasing tube pitch.

New fixture applications for compact twin tube fluorescent lamps

New and efficient luminaires have been designed for compact, twin tube-type fluorescent lamps. One important example of these new fixture applications is the 1*1 ft luminaire with three 18 W high lumen twin tube fluorescent lamps. Performance comparisons with this luminaire type have been made using different 18 W lamps operating on preheat and rapid start-type ballasts. The preheat (switch start) measurements were made at 240 V and 50 Hz using single lamp reactor type ballasts, and the rapid start measurements were made at 120 V and 60 Hz using three-lamp electromagnetic and electronic ballasts. In addition, comparisons are made against an older technology 150 W incandescent downlight fixture with approximately the same light output level indicating the substantial improvement in system photometric performance for these new compact fluorescent light sources.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A magnetohydrodynamic simulation of the formation of magnetic flux tubes at the Earth's dayside magnetopause

We have studied dayside magnetic reconnection by using a three‐dimensional global magnetohydrodynamic simulation of the interaction between the solar wind and the magnetosphere. We found two different mechanisms for the formation of magnetic flux tubes at the dayside magnetopause which depend on the orientation of the interplanetary magnetic field (IMF). The dayside magnetic flux tubes occur only when the IMF has a southward component. A strongly twisted and localized magnetic flux tube similar to magnetic flux ropes appears at the subsolar magnetopause when the IMF has a large By component. When the By component is small, twin flux tubes appear at the dayside magnetopause. Both types of magnetic flux tube are consistent with several observational features of flux transfer events and are generated by antiparallel magnetic reconnection.

Development of a new universal neuroangiographic unit.

A new neuroangiographic unit has been developed with use of a "C" type gantry, which is capable of rotation and angulation for various angiographic projections. Two sets of a twin focal X-ray tube and an imaging system are mounted on the gantry. Each imaging system consists of a 9 inch image intensifier and a 14 X 14 rapid film changer, which can be exchanged in position rapidly. Stereoscopic magnification and stereoscopic contact angiography, fluoroscopy and DSA are performed in monoplane and biplane and switched over to each other expeditiously and easily. The detailed angiographic information is obtained with lower complication rate and lower exposure to patients. Interventional neuroradiologic procedures are performed efficiently on this unit.