TUNNELING & UNDERGROUND SPACE ENGINEERING
Year:2017 | Volume:5 | Issue:2 |Papers Count:6

Simulation of fluid flow within tunnel is an appropriate and relatively cheap way to investigate the spreading of the pollutants and the efficiency of tunnel ventilation system. In this research, the tunnel of Tehran-Tabriz line is studied from this aspect. This tunnel is 8 km long and 32 m width, and the locmomotive ER24PC passes from it. Ventilation of this tunnel is of great importance because of considerable length of the tunnel with 4 parallel lines in urban area and because of passage of the old diesel locomotives through it. Fluent software is used for numerical analysis and modeling of a length of 200 m of the tunnel. The species of each gases in combustion product mixture of ER24PC locomotive are obtained using emission standard EU III A. The molar ratio of pollutants in the exhaust of the locomotive is calculated using equilibrium equation of combustion, and then, is entered to the non-premixed combustion toolbox of the software to specify the volume fraction. In the critical case, two trains with a speed of 50 km/hr moving toward each other in the parallel lines are considered. The simulation is carried out by using dynamic mesh and UDF motion code. The simulation is validated by experimental work reported in references. The performance of ventilation system, temperature distribution along the tunnel and the effect of the motion of the train on spreading pollutants are investigated. Summary: In this study, simulation of moving ER24PC (Siemens) locomotive in three dimensional (3D ) mode is made by using dynamic mesh in the Fluent software. The modeling of moving locomotives is a new idea in the field of tunnel ventilation. Thus, the distribution of outlet pollutants is investigated in both length and cross sections of the tunnel due to the motion of the train, and also, the effect of the motion of the train on spreading CO and Nox is investigated.Introduction: Ventilation of tunnels is important in two applications of traffic and fire mode. In recent years, some disasters due to tunnel firing, for example in Baku or Daegu metro, have occurred that show the importance of fire and smoke ventilation in tunnels. The initiation of fire in tunnel produces a huge amount of smoke, which moves to the ceiling due to the buoyancy effect, and spread out in both sides. The task of tunnel ventilation system in this critical mode is to push the smoke into one side, and make a safe passage for passenger escape or rescue team.Methodology and Approaches: In this study, locomotive emissions are simulated as a moving point and as a result, pollutants spread in 3D space. The combustion products of the locomotive are obtained by considering the MTU engine exhaust emissions and using Emission standard EU III A. The volume fraction of each pollutant is calculated from the equilibrium equation of combustion and is entered into the non-premixed combustion toolbox of the Fluent software. The moving train is modeled using dynamic mesh and employing UDF motion code. The velocity of the trian is considered to be 50 km/hr and two crossings against train are considered as a critical mode.Results and Conclusions: In the case of no forced ventilation in tunnels, it can be seen that the motion of trains induces air flow passing above the train that causes the spread of smoke behind of the train. The maximum temperature and concentrations of pollutants happen above the chimney of the locomotive, and decrease toward the start point of motion. The temperature and concentration values of pollutants in the tunnel cross-section are independent when the incoming trains are at the near wall line or center line. The results also show that the concentrations of toxic gases from the ER24PC locomotive do not reach to the critical values as long as the locomotive in the tunnel is moved.

Summary: The aim of this paper is to redesign the main gate support system to control the floor heave in Tabas coal mine. This tunnel is located in the No.2 eastern panel of Parvadeh.1 Tabas coal mine (E2M.G). To reach this main, the amount of floor heave and the influence of face advance on the floor heave magnitude have been evaluated by FLAC3D software. The results have shown that the floor heave magnitude at control points, without considering the working face effect, is 45 cm, and when the distance between the panel working face and the control points is 5 meters, the floor heave magnitude will reach 145 cm. Finally, steel set (type IPB180) has been proposed as a support system. Furthermore, the excavation of main gate floor in curvilinear shape with 40 cm depth and the installation of 8 bolts in the floor have been suggested. In this condition, the amount of floor heave at a distance of 5 m in front of the panel working face decreases to lower than 20 cm.Introduction: One of the problems in mechanized longwall mining method is the existence of inappropriate ground condition such as swelling and squeezing in tail gate and main gate tunnels. Tunnel excavation in these grounds with presence of high induced stresses, which are applied on support system, will encounter many difficulties.Methodology and Approaches: Numerical modeling has frequently been used in various fields of engineering and its results are usually accepted by various organizations. In this paper, three dimensional (3D) modeling of main gate tunnel of No. 2 eastern panel in Tabas coal mine was carried out using FLAC3D software. For modeling and determination of the amount of floor heave, Mohr - Coulomb and strain softening behavioral models were used and amount of floor heave was achieved in two states of regardless the face advancement and with considering the face advancement effect.Results and Conclusions: The results of numerical modeling with face advancement indicate that vertical and horizontal stresses in the tunnel floor, respectively, become 2 to 2.5 and 1.5 to 2 times greater than the stresses caused by face advancement, and thus, it is one of the effective factors on amount of tunnel floor heave. Moreover, the numerical modeling results have shown that the best support system to control the tunnel floor heave is as follows:- Using 4 steel bolts with 3 m length and 0.5 meter spacing in each row and 1 m row spacing in both sides of the tunnel roof - Using 4 rock bolts with 7 m length and 0.5 meter spacing in each row and 1 m row spacing in the center of roof- Using 4 fiber glass bolts with 4 m length and 0.5 meter spacing in each row and 1 m spacing in the right wall of the tunnel- Using 4 fiber glass bolts with 4 m length and 0.5 meter spacing in each row and 1 m spacing in the left wall of the tunnel- Using IBP180 steel set

Summary: This study is to simulate the rock fragmentation process with disc cutter in linear cutting machine (LCM) using the numerical method of finite element. The numerical model of rock and disc cutter was built according to the experimental settings, and then, validated with the test data. The rock model was built for Indiana Limestone as it was used in experimental study. The comparison of cutting forces obtained from the numerical simulation with those obtained from LCM test showed a good agreement between the simulation and the test results.Introduction: Use of tunnel boring machine (TBM) for hard rock tunneling has been ever increased due to the growth of technology and society, as well as growing demand. The main role of disc cutters in this machine is rock cutting. An accurate estimation of the forces acting on the disc cutter is very important in machine design. To do so, the cutting forces acting on a single disc cutter as well as its performance in a specific rock are predicted using full-scale linear rock cutting tests. The results are then generalized for TBM design in the same rock.Methodology and Approaches: The commercial finite element code ABAQUS/CAE was used to perform the numerical simulations of the rock cutting process in LCM test. The forces acting on a fresh constant cross section disc and specific energy were simulated. For validation purposes, the results obtained from numerical model were compared with those of experimental results.Results: and Conclusions The model validity was checked by comparing the results recorded from the experiments and those results obtained from numerical simulation. All cutting forces obtained from simulation were located in the confidence interval of experimental data. The analysis results showed that cutting forces and cutting coefficient increased non-linearly with increasing disc penetration. A good agreement was obtained between the numerical results and experimental data. Moreover, the cutting forces obtained from the simulation showed a maximum deviation of 15 and 21% from the experimental average values for normal force in penetration depth of 5 mm and rolling force in 2.5 mm, respectively.

Summary: Due to the importance of tunnels in urban transport network and their increasing development, their design or construction is always faced with new technical problems or concerns. One of these concerns is the effect of dynamic loads generated by the movement of the train on the tunnel. The goal of this research is to provide the stability analysis of a section of the tunnel of line 3 of Tehran metro by three dimensional (3D) numerical modeling.Introduction: By increasing the urban population, construction and development of urban infrastructures are becoming more essential. Construction and development of subway tunnels in urban areas have always been facing with serious restrictions and problems. One of the problems, investigated in this research, is the intersection of subway lines with railway lines. The purpose of this research is to provide a proper method for construction of some parts of the tunnel of line 3 of Tehran subway passing below the global railway lines of Tehran-Ahwaz.Methodology and Approaches In the initial design stage, a part of the tunnel of line 3 of Tehran was designed using cover and cut method and by considering its technical advantages in implementation and reduction of costs, and thus, the cover and cut method was suggested for implementation of the project. In order to analyze the stability of this part of tunnel, the dynamic load due to the motion of a train was applied in the simulation process, and as a result, a function for the dynamic load of this motion was obtained. This function was applied in the built numerical model of the tunnel by FLAC 3D software. Then, the obtained results of modelling was compared with two analytical methods to determine the stability of the tunnel using velocity of the train, weight of the wagon, number of the wagons and damping in the environment in the most critical situations.Results and Conclusions: The accomplished analyses in this research suggest that the tunnel stability is in an acceptable condition, and there is no need to reinforce the support system. Furthermore, considering the need to expedite the construction and restoring railway on the tunnel, the cover and cut method has been suggested to implement the project.

The liquefaction is one of the most complicated and destructive phenomena that occurs during earthquake and causes failure and destruction in various structures. Granular and saturated sediments in seismic hazard zones are susceptible to this phenomenon. Although liquefaction and its effects on surficial structures have been extensively studied, relatively less attention has been paid to its effects on subsurface structures. Moreover, due to recent developments in subsurface structures such as subway and traffic tunnels in seismic hazard zones of developing countries such as Iran, the investigation of liquefaction effects on subsurface structures is of great importance.Summary: In this paper, liquefaction potential of east-west part of line 7 of Tehran subway has been investigated. For the ease of this investigation, this part of tunnel has been divided into six parts, each of which has separately been evaluated. Liquefaction potential has been evaluated based on shear wave speed and finite element modeling software called PLAXIS. Finally, the obtained results from various methods have been compared.Introduction: Liquefaction and its effects on surficial structures have been extensively investigated. However, relatively less attention has been paid to its effects on subsurface structures. In addition, considering the construction of subsurface structures such as subway and traffic tunnels in seismic hazard zones, the investigation of liquefaction effects on subsurface structures appears to be significant.Methodology and Approaches: In this paper, liquefaction potential of east-west part of line 7 of Tehran subway has been investigated. Due to the ease of investigations, this part of the tunnel has been divided into six parts, each of which has separately been evaluated. In this evaluation, three types of analytical methods, including the seed method, the novel method of Vancouver, and the Intermediate method which is the average of several conventional methods have been employed. Then, liquefaction potential has been evaluated based on shear wave speed in soil. Finally, a section of tunnel has been modeled and investigated using the finite element modeling software called PLAXIS.Results and Conclusions: After obtaining the results of various methods, these results have been compared. The results of finite element method are in good agreement with the results of analytical methods used in this study.

The purpose of this research is to obtain the requirements of non-operational defenses in the design of metro station. This paper presents some criteria to reduce damages resulting from the enemy threats by using passive defense.Introduction Subways as one of the critical and practical infrastructures with dual functions can be considered as a settlement for people during crisis and threat. The principles of safety and protection against natural and unnatural threats should be carefully regarded in the design of subways. Thus, to provide safety and protection against threats, the passive defense requirements in subways should be considered.Methodology and Approaches The research methodology is of descriptive-analytical type and the technique used in this research is Delphi. The statistical population of the research is all the experts in the field of passive defense and architecture, and 12 individuals, for instance, have been selected from these experts. The average of the views of the members of the Working Group 4 indicates a high agreement among them.Results and Conclusions The results of this research show that among the proposed architectural requirements of passive defense, the subway station is used as a refuge in the time of crisis with an average of 4.91 and has the highest score. The use of suitable bends with respect to engineering principles (90 degrees bends) with score or importance of 4.84 is the second requirement among the passive defense requirements. The maximum accessible radius to the station entrance is 500 meters. The third priority is the architectural requirements of the defense, and the provision of space and space to meet the essential needs and services of the people is the fourth priority. The necessity of self-sufficiency of ventilation systems, the existence of multiple ventilation ducts to deal with airborne bombs, emergency exits with the depth greater than the depth of the asylum seekers' location, adequate width and safety of tunnels for passage of persons, are the next priorities of these requirements. Finally, the necessary electrical systems and lighting of tunnels, the use of security and security systems, and the existence of an independent and emergency communication network for communication with the environment with score averages of 4.28, 4.18 and 4.11, respectively, are the last priorities of these requirement.