Distance improvement between non-level crossing tunnels by numerical method - case study of Tehran crossing subways line 6 and 7
hamid
sherizadeh
Master student
author
Saeed
Dehghan
Assistant professor
author
text
article
2017
per
In non-level crossing tunnels, optimization of distance between tunnels is one of the most important factors. In theory, the more distance between the tunnels, the more appropriate it is, but in terms of operation, the closer the tunnels are to each other and to the surface, as long as there is no damage to other subsurface structures, the more suitable it is. The main objective of this study is to optimize and determine the minimum allowable distance in intersecting of non-level tunnels. To achieve this objective, three dimensional numerical models were developed by MIDAS GTS NX (a finite element numerical analysis software) and the geometry and the initial distance of tunnels were considered according to the basis of information received from the intersection of Tehran subway tunnels, no 6 and no 7. In this research, two main scenarios have been examined: in the first, a deep tunnel getting closer to a shallow tunnel and in the second, a shallow tunnel to a deep tunnel. In each scenario, several numerical models were developed where each tunnel get closer to each other for 40 cm. This process continued until ground subsidence or strain in the models exceed the permissible level and where there is no need to change any of designed properties of the lining of the tunnels. The results show the second scenario is more suitable, especially in the case of ground subsidence. In this scenario the distance between the tunnels can be reduced to 80 cm without any change in the structural parameters of lining of both tunnels. The results of this study can be considered in designing and excavating of non-level crossing tunnels. Summary First, all the assumptions considered is intended. Then, literatures were reviewed and the project is introduced precisely. Finally the 3D model by finite element software was done, and improvement of distance between tunnels in two scenarios was investigated. At last after investigating a different parameters the best distance between tunnels has been chosen. Introduction This research has been done by numerical finite element method. According to subway networks development, constructing the underground structures has always been a challenge. In this research one of the most important challenges (improvement the distance between tunnels) has been answered. Methodology and Approaches Because there are a various factors affecting the interaction of non-level crossing tunnels, so the best method for investigating these problems, are numerical models. And because the medium that tunnels are constructed in, is continuum, the finite element method for solving the problem is used. Due to 3D nature of the problem, 3D modeling is used. Results and Conclusions As mentioned before, the best scenario is to move the shallow tunnel downward toward the deep tunnel.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
1
15
http://tuse.shahroodut.ac.ir/article_1050_18169a375cc444f6bf289d383a9b6766.pdf
dx.doi.org/10.22044/tuse.2017.4585.1274
Numerical modeling of the Seismic Response of Shallow Circular Tunnels in Homogenous Layered Ground Using FEM Code ABAQUS and Compare the Results with the Analytical Solutions
Ali
Roozitalab
Instructor/Khatam University of Technology
author
Seyed Amin
Asghari Pari
Assistant Professor/Civil Engineering Department-Khatam University of Technology
author
Seyed Ali
Asghari Pari
Instructor/Civil Engineering Department-Khatam University of Technology
author
Sasan
Motaghed
Department of Civil Engineering, Faculty of Engineering, Khatam University of Technology, Behbahan, Iran.
author
text
article
2017
per
Summary Seismic response of circular tunnels embedded in homogenous ground has been studied using the FEM code abaqus. Results show that the tunnel embedded in one layered ground has a completely different behavior in comparison with the same tunnel embedded in two( or more) layered ground. Introduction In this study, the effect of ground stratification on the seismic response of circular tunnel''s lining is investigated, as most practice-oriented studies consider homogeneous ground. The above mentioned situation has been argued detailed in the coming content. Methodology and Approaches A finite element plain-strain model of a circular tunnel''s cross-section embedded in an one and two-layered ground is used to highlight the influence of stratification on the tunnel''s seismic response at the crown, springline and invert points. The finite-element mesh grid simulates a 30-meter soil mass in a plain-strain condition with amount of 31226, 4-node rectangular elements in a rugged limestone rock. Ground and tunnel both are simulated with Single-phase linear elastic materials and Wang’s closed form solution is used to predict the seismic response of tunnel’s cross section. The model only considers the vertical propagation of shear waves in the visco elastic layers on a hard rock bed. The degrees of freedom at the bottom of the floor are completely restrained, because displacements are calculated from the base. Results and Conclusions The main parameters govern the calculated loads derived from analytic solutions are the compactness C, the F flexibility ratios, and the maximum rate of free shear strain ɣ. Results prove that the conditions of the ground layers, specially the amount of layers, play an important role in the situation of seismic forces encountering the tunnel lining. The layers interface was placed at the crown, center and invert level. . Models clarify that when the tunnel is fully embedded in one of the two consecutive layers, the seismic forces created in lining may vary significantly in comparison with the case that we have only one layer for tunnel to be embedded in. Furthermore if the tunnel intercepts both layers, maximum lining forces aggravation occurs when the lower layer is very stiff. When the tunnel passes through both layers of soil, the values of R follow the single-layer lining response for , otherwise less R values are obtained. For the lower stiffness of the layers, the R values obtained are almost unaffected by the higher hardness values, EV.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
17
26
http://tuse.shahroodut.ac.ir/article_1072_a37b8dbb13eda4eec6300bdcd4178d77.pdf
dx.doi.org/10.22044/tuse.2017.4653.1276
Numerical study of effecting parameters on pressure distribution in contact zone of rock and disc cutter in linear cutting process
Reza
Mohammadi
student/University of Zanjan
author
jafar
khademi hamidi
عضو هیئت علمی گروه مهندسی معدن دانشگاه تربیت مدرس تهران
author
فرهاد
صمیمی نمین
عضو هیئت علمی گروه مهندسی معدن دانشگاه زنجان
author
text
article
2017
per
Estimation of cutting forces acting on a disc cutter while cutting rock has been used for cutter head design and performance prediction of tunnel boring machines (TBMs). On the other hand, cutting forces is resulted from pressure in contact zone between disc cutter and rock. In this study, numerical modeling of rock cutting procedure with disc cutter by applying commercial finite element code ABAQUS is performed and in order to validate this model, contact zone pressure between disc and rock was compared by Rostami(1997) ‘s semi-empirical model. Modeling Shows 14 error percentage that confirms good relation between two models. The other result of this modeling is study the effective geometrical parameters of disc in pressure distribution of contact zone area in linear rock cutting procedure. Summary In this Study, linear rock cutting procedure of a single disc cutter was modeled by Commercial finite element code ABAQUS/CAE. Numerical models of rock and disc with perfect match by laboratory testing of linear rock cutting test by Rostami(1997) was built and finally validated. Pressure distribution of cutting zone with considering of non-loading zones was studied and was compared with semi-empirical model of Rostami(1997). With lower than 14% of error percentage comparing laboratory result, This models shows a perfect match. Also, geometrical parameters of disc cutter was studied to find the effects on pressure distribution zone of contact area. With a longitude and a latitude cross sections of rock model in cutting path, it was concluded that with increasing edge and angle of disc tip, micro cracks was formed in rock. Although the disc diameter causes increasing weight of disc, resulted pressure distribution has less changes. Introduction Rock cutting procedures is an indentation of a cutter into rock that formed a pressure bubble immediate beneath cutter in rock and finally a soft powder is formed around the cutter. This bubble develop a crack pattern to rock material. In 1993, Rostami & Ozedmir believe that this bubble has a hydrostatic pressure forms that has linear behavior but in 1997 by calibration of disc and do more rock cutting tests, found out the other form of pressure bubble and non-loading zones exist in rear and forward of disc cutter in cutting procedure. Methodology and Approaches In order to modeling linear rock cutting procedures, Commercial finite element code ABAQUS/CAE was employed and for validating that, laboratory linear rock cutting test by Rostami (1997) was considered. Rock and disc cutter models was built in ABAQUS GUI module and to simulate rock behavior of rock model, Strength criterion with linear equation of state was implemented to material model. Boundary Condition for disc cutter was similar to TBM’s working status with linear velocity of 2 meter per seconds and angular velocity of 9.3 radians per seconds. Results and Conclusions The results from Numerical modeling of rock cutting that validated by laboratory test of Rostami (1997) shows prefect match with semi-empirical model. Even though this model can be employed in other applications of TBM designs, more study is needed to find out deeper issues of rock cutting procedures.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
27
42
http://tuse.shahroodut.ac.ir/article_1073_6ee65f80b3902975ad55ba258fab044c.pdf
dx.doi.org/10.22044/tuse.2017.4979.1288
Parametric analysis of horse-shoe hydraulic tunnels with respect to influential elements in concrete lining designing employing complex potential functions
Ali Reza
Kargar
دانشگاه تهران
author
Reza
Rahmannejad
دانشگاه شهید باهنر کرمان
author
Mohammad Ali
Hajabbasi
دانشگاه شهید باهنر کرمان
author
text
article
2017
per
Summary In this study, horse-shoe tunnels have been analyzed with respect to the ratio of stiffness, relative thickness, and the ratio of in situ stress under the presence of earth pressure, and water pressure inside tunnels. Surrounding rock mass and concrete have been assumed as elastic materials, and complex potential functions along with conformal mapping have been used in the investigation. it was observed that an enhance in concrete stiffness resulted in increasing circumferential stress at key points. A critical value for lining thickness was obtained that for values smaller than which the circumferential stress exceedingly increased. Introduction Tunnels are the main infrastructures widely used for transportation, water passage, and other purposes such as underground mining. Among various tunnels configurations, horse-shoe tunnels are more popular for their merit of suitable stress distribution in surrounding rock, which makes them capable of maintenance in a wide variety of rocks, from soft to hard ones. Here a sensitivity analysis was conducted on the most important parameters for lining design of hydraulic horse-shoe tunnels. These parameters consist lining thickness, rock and concrete stiffness, initial in situ stress ratio and inside water pressure. To this aim, Muskhilishvili complex potential functions combined with conformal mapping were used. Concrete lining and the surrounding rock mass were assumed as linearly elastic materials, and the problem was tackled based on a plane strain scheme. Methodology and Approaches The impact of variation of input parameters were investigated on circumferential stress produced through lining and rock mass regions. Muskhilishvili complex potential functions along with conformal mapping were used in order to implement this investigation. Results and Conclusions It is demonstrated that increasing the ratio of stiffness will enhance circumferential stress at key points in the concrete, while reduce that at the roof in the rock mass. It is observed that for high ratio of stiffness when relative thickness is less than 0.04, the circumferential stress boosts, which should be evaded in design. An enhancement in the ratio of in situ stresses also raised circumferential stress at the roof, and reduced that at the wall. The investigations implied that the amount of the variations of circumferential stress corresponding to a ratio of in situ stress, where the ratio of stiffness is less than 1, were exceedingly lower than that when the ratio of stiffness is more than 1.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
43
56
http://tuse.shahroodut.ac.ir/article_1085_4cec8c2b177dea082d59ec5745e71516.pdf
dx.doi.org/10.22044/tuse.2017.4921.1286
Assessment of rock mass caveability in block caving mining method, using Rock Engineering Systems (RES)
amir
azadmehr
department of mining, Mining Eng., petroleum and Geophisics. Shahrood university of technology
author
Seyed Mohammad Esmaeel
Jalali
Department of Mining engineering, petroleum, geophysics, Shahrud university of technology
author
text
article
2017
per
Assessment of rock mass caveability is one of the important factors in the success of the block-caving mining. prediction of rock mass caveability is complicated due to the wide range of effective factors and the lack of complete knowledge of the impact of each factor on the rock mass caveability. Existing methods do not consider all the factors affecting the caveability process. This study uses the Rock Engineering systems (RES) approach to assess the rock mass caveability. After the implementation of the rock engineering system and ranking the influencing factors, the caveability index for selected mines was calculated. The results of this study have shown the sufficiency of RES approach in taking into account of all effective parameters. Introduction In mining methods based on caving of ore such as block caving and sublevel caving, caveability of ore and surrounding rocks is of great importance. If the caveability of ore, would not properly evaluated it will impose high cost and losing of time on mining companies. A major challenge in developing of existing caveability predicting methods is the taking into account of the values related to geomechanical, environmental, geometric and operational factors of rock mass, with a simple yet efficient method. Methodology and Approaches RES is a powerful system approach to study the effect of influencing factors on the performance of an engineering system. The first step of the method is to establish interaction matrix and coding of the matrix. The principal factors considered relevant to the caveability have listed along the leading diagonal of a square matrix and off-diagonal terms have been coded by ESQ method. Then by Using RES approach the effective parameters on caveability have ranked. In the next step caveability index of Elteniente, Kemess and Ironcap mines, determined and compared with the results of well-known experimental methods, as the Laubscher caving chart, the extended Mattew’s stability graph and Stewart and Forsyth methods. Results and Conclusions The results of this study have shown that Geomechanical factors are the most dominant and geometric factors are the most subordinate factors in the system. In addition, geomechanical and environmental factors have the highest and the least interaction on the system, respectively. Furthermore, although the hydraulic radius is different in experimental methods, but follows the same trend and there is a good agreement between the results of rock engineering systems and experimental methods there. At last a classification for the caveability index has introduced.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
57
78
http://tuse.shahroodut.ac.ir/article_1116_ef255731ca9211beab441c0d3bbfd844.pdf
dx.doi.org/10.22044/tuse.2017.6281.1325
Effects of the excavation pattern on stress reduction factor in convergence confinement method in soft ground- case study Karaj metro line 2
محسن
موسیوند
دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران
author
محمد
ملکی
دپارتمان فنی و مهندسی-دانشگاه بوعلی سینا-همدان- ایران
author
مسعود
نکویی
دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران
author
محمد رضا
منصوری
دانشگاه آزاد اسلامی واحد علوم و تحقیقات تهران
author
text
article
2017
per
Summary Tunnel construction is in demand in many large cities in the world that facing a problem with traffic. Among 2D methods to tunnel analysis, the convergence–confinement method (CCM) is the most accurate method that analyzes the tunnel-ground-support interaction. Previous researchers’ studies have been done mostly to evaluate the affected parameters on CCM. But few of them are investigated how effected the shallow tunnels (anisotropic stresses) with any cross section shapes to the confinement loss values in all around perimeters of tunnel section. Introduction The aim of this study is to evaluate the effect of excavation pattern on stress reduction factor in shallow tunnels with horseshoe cross section shape in soft ground Methodology and Approaches For this purpose, at first, by considering the line two Karaj subway cross sections, using back analysis, calibration of Mohr-Coulomb constitutive model parameters was determined. Then, by considering common type of excavation patterns (full face and multi face), the three different curves, ground reaction curve, longitudinal displacement profile and support characteristic curve, which is required to obtain the stress reduction factor. This is done using a series of numerical analysis by FLAC 2D and FLAC 3D code. Back analysis is done to obtain soil parameters of Karaj subway line two. The stress reduction factor values are investigated in each excavation patterns in different points around the tunnel. Finally, the vertical and horizontal movement induced mentioned effects are evaluated in each tunnel stages. Results and Conclusions The results of this study show the good agreement of parameters obtain from back analysis to instrumentation data. Tunnel excavation pattern has significant effects on determining stress reduction factor in convergence confinement method for multi stage tunneling excavation. The results of analysis are shown a good capacity of model in reproduction of better and more precise tunnel behavior in shallow tunnels.
Tunneling & Underground Space Engineering
Shahrood University of Technology &
Iranian Tunneling Association
2322-3111
6
v.
1
no.
2017
79
94
http://tuse.shahroodut.ac.ir/article_1118_3bf3427179e802b3dffdbc0662b9b088.pdf
dx.doi.org/10.22044/tuse.2017.5428.1303