فهرست مطالب شکرالله زارع

This paper investigates the effect of the method of applying pre-support in the numerical modeling of tunnel and ground interaction. Two main numerical approaches of linear pile and equivalent zone elements were considered for the modeling of pre-support in front of the advancing tunnel face. Both of these approaches were applied for one of the Tehran-Shomal Freeway as the case study of numerical modeling. The results of numerical models were compared to investigate the effect of pre-support modeling approaches. The vertical deformation of numerical models with different approaches shows a meaningful consistency; therefore, it is concluded that both of these methods of linear pile element and equivalent zone element can be applied to numerical modeling demands for other studies.

Surface settlement induced by tunneling is one of the most crucial problems in urban environments. Hence, accurate prediction of soil geotechnical properties is an important prerequisite in the minimization of it. In this research work, the amount of surface settlement is predicted using three-dimensional numerical simulation in the finite difference method and Artificial Neural Network (ANN). In order to determine the real geotechnical properties of soil layers around the tunnel; back-analysis is carried out using the optimization algorithm and monitoring data. Among the different optimization methods, genetic algorithm (GA) and particle swarm optimization (PSO) are selected, and their performance is compared. The results obtained show that the artificial neural network has a high ability with the amounts of R=0.99, RMSE=0.0117, and MSE= 0.000138 in predicting the surface settlement obtained from 150 simulations from randomly generated data. Comparing the results of back-analysis using the optimization algorithm, the genetic algorithm shows less error than the particle swarm algorithm in different initial populations. In all cases of analysis, the calculation time for both algorithms lasts about 5 minutes, which indicates the applicability of both algorithms in optimizing the parameters in mechanized tunneling in a short time.

One of the important cost items in mechanized tunneling is the cost of repairing or replacing the disc cutters that have suffered from normal wear during the boring of the hard abrasive rocks. For inspecting the health of the disc cutters, the boring operation shall be stopped, and after checking, the worn disc cutters may be replaced. In this work, the dynamic process of the TBM boring in the jointed rocks is simulated using a real-scale numerical analysis based on the rock fracturing factor using the discrete element method (DEM). The stress distributions induced within the disc cutters as well as the development of the plastic zones in the rock are investigated and compared with the actual results recorded in the Kerman water conveyance tunnel (KWCT). The numerical results indicate that the increase in the rock fracturing causes a decrease in the induced stresses and an increase in the size of the plastic zone. In other words, a higher penetration rate as well as more lifetime for disc cutters can be achieved in highly fractured rocks. Moreover, the average von Misses stress in the disc cutters in the highly fractured rocks is predicted about 16-23% less than stress induced in the slightly fractured rocks. Due to the TBM tunneling, the volume of the plastic zone as well as the actual penetration depth in the highly fracturing rocks are also about 40% and 42% higher than in the slightly fractured rocks under applying the same TBM parameters, respectively.

Despite many improvement in the underground construction by mechanized ‎methods and the whole section, the drilling and blasting still plays an important ‎role in the construction of tunnels and mines. In addition to various advantages ‎such as flexibility and low capital cost, this method also has disadvantages, one of ‎which is the expansion of the blast damage zone around the underground ‎structure, which leads to increased joints and cracks in the surrounding ‎environment and consequently reduced resistance and increased permeability ‎also In some cases land subsidence occurs . Various factors affect the damage ‎zone. Various methods such as measurement, experimental and modeling ‎methods are available to investigate these factors. In this paper, numerical ‎modeling has been done for three different state of drilling a. In addition to a brief ‎mention of different factors affecting the damage zone, it is determined that the ‎maximum impact on the damage area is related to tensile strength and cohesion ‎of rock. In addition, the effect of rock geological strength index (GSI) has been ‎investigated as one of the important factors in recognizing rock mass and the ‎effect of reducing the damage area with increasing GSI has been observed.‎

According to the results, as the injection duration and the pumping rate increase, the fracture length increases and the maximum length created is about 22 meters by applying a fluid with a viscosity of one centipoise during 5 minutes injection time and the rate of 35 barrels per minute or similarly by the same fluid with 18 minutes injection time and the rate of 10 barrels per minute. 

Hydraulic fracturing if properly implemented can be one of the least costly ways to increase the maximum production of the reservoir. Due to the complexity of the hydraulic fracturing process, various modeling has been performed to find the closest predictions of the actual fracture characteristics. Linear elastic fracture mechanics (LEFM), adhesion zone method, and plastic criteria can be used to evaluate the fracture onset time and its expansion in rock. 

To investigate the effect of injection duration on fracture growth, fluid was injected into the well with a viscosity of 1 cp and an injection rate of 0- 10 barrels per minute for periods of 5, 8, 10, 12, 15, and 18 minutes. This injection is made by drilling a well in the middle part of the reservoir. In the first 5 seconds, the injection rate increases linearly from zero to 0.07 barrels per minute and remains constant until the end of injection time. This distribution of injection rate over time is chosen to avoid sudden pressure. As the injection begins, the fluid pressure within the fracture increases, and as the fracture pressure is reached, fracture occurs. 

The purpose of designing hydraulic fracturing operations is to make some predictions to optimize these operations. There are five important factors to design for a hydraulic fracture: the length, height, and fracture opening that the propane holds, the fracture initiation pressure, and the fracture orientation. Four of these critical parameters are derived from hydraulic fracture modeling, so modeling provides 80% of the required solutions.The main input parameters for modeling hydraulic fractures are surface stresses, pore pressure, Young's modulus, Poisson's coefficient, porosity, permeability, angle of friction, and rock adhesion, and parameters related to rock fracture mechanics such as fracture energy, toughness, and components. As the injection duration and pumping rate increase, the fracture length increases, and the maximum length created for a fluid with a viscosity of one centipede at an injection of 5 min at 35 barrels per minute or 18 min at 10 barrels, is about 3 meters high while its maximum height is about 70 meters. Also, the maximum fracture opening in its opening is about 1 mm. Fluid viscosity affects the fracture width more than its length and also increases with the fracture width viscosity.

The purpose of this work is to present an approach for the probabilistic stability analysis of tunnels considering the heterogeneity of geo-mechanical properties. A stochastic procedure is followed to account for the variability in the rock mass property characterization. The finite difference method is coupled with the Monte Carlo simulation technique to incorporate the randomness of rock mass properties. Moreover, a particular performance function is defined to investigate the excavation serviceability based on the permissible deformations. In order to validate the analysis, the probabilistic and the deterministic results are compared with the in-situ measurements. It can be observed that in both the probabilistic and deterministic analyses the largest displacements occur in the invert. In contrast, the smallest displacements are recorded in the sidewalls. Utilizing the performance function, the probability of failure for the invert, crown, left, and right wall is estimated as 100%, 68.8%, 16.2%, and 20.9%, respectively. Comparing the measured and calculated convergences, it is conjectured that the deterministic analysis underestimates the displacements, while the measured values are very close to the mean values predicted by the probabilistic analysis. The results obtained indicate that the presented approach could be a reliable technique compared to the conventional deterministic method.

Global sensitivity analysis is one of the beneficial and useful tool to identify the uncertainty of input variables that has been extremely investigated in different science such as simulations. Sensitivity analysis is an essential step in the production of meta-model, which, by identifying effective parameters in tunneling, reduces the time and computations required. In this paper, sensitivity analysis was carried out on geotechnical and operational parameters of EPB mechanized tunneling in soft soil. So, the tunneling processes were modeled using a finite difference method in FLAC 3D software, and the numerical model was validated by the monitoring data obtained from the East-West route of Tehran metro 7 line. The sensitivity analysis by using elementary effect Morris method was performed on the 6 input parameters and three parameters (face pressure, specific gravity and cohesion of the soil layer which the tunnel was excavated) were selected as effective and sensitive parameters in the maximum surface settlement. Then to construction of meta- model, 100 samples were generated from effective parameters using the Latin Hypercube method. After numerical simulation for each sample, the simulation results were used for surface settlement prediction by using artificial neural network. The results showed that the prediction of the meta-model based on the artificial neural network and the numerical model for the data in the design phase corresponded about 98%.

Hydraulic fracturing (HF) and hydraulic testing of pre-existing fractures (HTPF) are efficient hydraulic methods in order to determine the in-situ stress of rock mass. Generally, the minimum (Sh) and maximum (SH) horizontal principal stresses are measured by hydraulic methods; the vertical stress (SV) is calculated by the weight of the overburden layers. In this work, 37 HF and HTPF tests are conducted in a meta-sandstone, which has about 10% inter-layer phyllite. The artesian circumstance, considerable gap between the drilling and hydraulic tests in the long borehole, no underground access tunnel to rock cavern at the early stages of projects, and a simplified hypothesis theory of HF are the main challenges and limitations of the HF/HTPF measurements. Due to the instability in the long borehole, the drill rig type and borehole length are revised; also TV logger is added to the process of selection of the test’s deep. The HF/HTPF data is sequentially analyzed by the classic and inversion methods in order to achieve an optimum number of hydraulic tests. Besides, The SH magnitude in the inversion method is lower than the classic method; the relevant geological data and the faulting plan analysis lead to validate the SH and Sh magnitudes and the azimuths obtained by the classic method. The measured SH and Sh magnitudes are 7-17 MPa and 4-11 MPa, respectively; the calculated vertical stress magnitude is 6-14 MPa at the test locations. Indeed, the stress state is (SH > SV > Sh), and SH azimuth range is 56-93 degrees.

The overall purpose of this study is to use probabilistic methods for the estimation of the advanced rate of full-face tunnel boring machines. To collect appropriate input parameters, Monte Carlo Simulation was utilized. Then, the calculation phase was conducted applying established models on input data and probability density functions of output data were obtained. The results show that the average advance rates calculated by QTBM and CSM models were closer to the average value of the actual advance rates. In addition, using probabilistic methods in combination with TBM prediction models helps to estimate the range of advance rates more confidently.

Hydraulic fracturing based on the use of guar gum water-base fluid with appropriate viscosity has been recognized as a viable solution for extracting oil and natural gas from the reservoir due to its unique benefits such as low cost and proppant carrying capacity. However, the lack of knowledge of reservoirs fractures has challenged field applications. Therefore, the purpose of this study was to investigate the effect of fluid injection rate on fracture pressure and geometry of fractures. To achieve this goal, a series of hydraulic fracturing experiments were performed on limestone rock samples using a guar gum water- base fluid. To investigate the effect of fluid injection rate, CT scan technology was also used to describe the geometric parameters of the fracture. The results of experiments show that with increasing fluid flow rate injected from 1 to 6 ml/min, breakdown pressure and fracture opening increase. As the volume of consumed fluid increases the breakdown time decreases. The findings of this study reveal that low guar gum-flow rates can create a better inter- connected fracture network than higher flow rates.

Evaluation of TBM performance is very important in estimating the cost and time of a tunnel project. Sensitivity analysis of a model is performed to examine the influence of the input variables on the output variables. In this study, results variability of main models of TBM penetration rate (PR) prediction have been investigated based on the geological and field performance data at Lar-Kalan water conveyance tunnel. The overall results indicate that increase of thrust force, CLI, RPM, porosity, and fracturing factor and the decrease of Q value, quartz content, unconfined compressive strength, tensile strength, induced biaxial stress on tunnel face, and RQD increases the PR. Sensitivity analysis has been evaluated on the basis of the two Tornado and Spider charts for different models, and the effect of the input parameters variation on the variation of the PR have been investigated and the parameters that have the greatest influence on the PR were specified. Among the geological conditions, the variation of the Q value, porosity, UCS, RQD and among the machine parameters, variation of the thrust force and RPM have the greatest impact on the variation of the penetration rate in the project.

Mechanized excavation of the large cross section tunnels in rock condition has some hazards. Machine purchasing costs, fault zones, water inflows, squeezing, face instability, and etc. are some of the hazards which may cause excavation stop for a long time. In addition to mechanized excavation advantages, machine inflexibility in the complex geological conditions, high investment costs, technical, geometrical and political risks are the major disadvantages. Due to the high investment costs in this method, assessment and ranking the mentioned hazards are of a great importance. In this study, the tunneling risks of Alborz Western Tunnel (AWT) has been investigated using the fuzzy multi criteria decision making methods. The AWT in Tehran Shomal Highway is one of the major country project that considered to be excavated by an EPB shield machine. By analyzing geological condition and survey of some specialist's point of view, in this study, 17 possible hazards have been identified, and assessed by fuzzy TOPSIS and ELECTRE methods. Results shown that insufficient experience in mechanized tunneling of the large diameter tunnel and gas emission in the tunnel and investment and purchasing the machine are the most important risks in the project.

In this work, we tried to automatically optimize the cost of the concrete segmental lining used as a support system in the case study of Mashhad Urban Railway Line 2 located in NE Iran. Two meta-heuristic optimization methods including particle swarm optimization (PSO) and imperialist competitive algorithm (ICA) were presented. The penalty function was used for unfeasible solutions, and the segmental lining structure was defined by nine design variables: the geometrical parameters of the lining cross-section, the reinforced feature parameters, and the dowel feature parameters used among the joints to connect the segment pieces. Furthermore, the design constrains were implemented in accordance with the American Concrete Institute code (ACI318M-08) and guidelines of lining design proposed by the International Tunnel Association (ITA). The objective function consisted of the total cost of structure preparation and implementation. Consequently, the optimum design of the system was analyzed using the PSO and ICA algorithms. The results obtained showed that the objective function of the support system by the PSO and ICA algorithms reduced 12.6% and 14% per meter, respectively.

Tunnel Boring Machine (TBM) is used widely to bore long tunnels in hard rocks. If you choose shield TBMs, precast concrete segments should be installed as permanent tunnel lining. This lining is inherently distinct and therefore in analytical and numerical analyses, the continuity assumption is not acceptable for simplifying. The segmental linings show certain behavior under various loads applied by rock, machine and tunneling processes (such as grouting). In this study, the behavior of segmental lining of Sabzkouh water conveyance tunnel has been compared to full (continuous) lining. In this paper, the behavior of tunnel segmental lining by assigning normal and shear stiffness values for longitudinal and circumferential joints of segments is compared with the continuous lining. The effect of the grouting pressure between rock and segments on the behavior of the tunnel segment is analyzed. Under uniform grouting load, the results of numerical modeling executed by finite difference method show maximum internal forces occur in the joints of segments. With increasing grouting pressure, axial force and bending moment in the joints of the segments is reduced. Moreover, the grouting pressure increases displacements in the segmental lining. In practice, this increase sometimes causes cracking or stepping between segments.

Among the significant discussions pertaining to the project design and planning, minimizing uncertainties is an important issue. Usually the uncertainties in subsurface projects arise from the unknown ground conditions which may cause the designer to fail to consider all the potential issues prone to occur during the construction procedure. Total time and cost uncertainties can be considered as the most important uncertainties; the time and costs are directly connected with thorough cognition of the subsurface conditions. Accordingly, in subsurface projects the actual time and costs are not ascertainable, and hence the probability methods should be used to assess such factors.In order to evaluate the uncertainties probabilistically, different tools (probabilistic models) have been introduced, including Decision Aids for Tunneling (DAT) tool. DAT was first introduced by Einstein; it was then developed by Prof. Einstein group and major advancements have been achieved in DAT research projects since then. The present study was undertaken on a Hamro road tunnel of 1310m length and cross section of $97 m^2$ as part of the under construction Sanandaj - Marivan road. In this paper, using DAT method and considering the pre-construction data of a Hamro tunnel, the probabilistic time and cost of the tunnel were predicted. In most cases in order to estimate the data needed for DAT method, a number of questionnaires were distributed among the tunneling experts and eventually the mean values of the respondents were applied to the model. Afterwards the time and cost obtained through DAT method were compared with the actual post-construction time and cost of the Hamro tunnel execution for model validation and reducing the uncertainty for the future projects. Finally, it was revealed that the obtained results of the DAT method has high similarity with the actual results, confirming the validity of DAT method for decreasing the total time and cost uncertainties in execution of future projects.

Increasing urban development and social needs for transportation systems bring about construction and extension of urban transportation systems. Considering the fact that the important part of costs relates to excavation and maintenance of tunnels, choosing the single or double tube tunnels is one of the most important decisions in urban tunneling. In case of using single tube tunnel, it should be large enough to accommodate a pair of trains and their appurtenances. However, in case of using twin tunnels, considering that each tunnel is meant to be used for one train, the sections of the tunnels can be smaller. The aim of this paper is to use 3D numerical models for line 1 twin tube tunnels and line 2 single tube tunnel of Tabriz metro to study the various aspects of using twin or single tube tunnels in urban areas. Various criteria have been considered such as: stability of the single and twin tube tunnels, subsidence occurred on the surface and nearby buildings, forces and moments exerted on the twin and single tube tunnels and their factors of safety. In this paper finite difference numerical method (FLAC 3D) has been used to model the tunnels of both lines. The results show that when considering the viewpoint of displacements occurring on the walls of tunnels, using a single tube tunnel with big section will be recommended. However, when the viewpoint of subsidence control and forces and moments acting on segmental linings is taken into account, the use of the twin tube tunnels will be advantageous.

Evaluation of interaction between new and existing underground spaces is one of the important problems in tunneling in urban areas. In some cases it is necessary to excavate tunnels close to each other’s. This، in turn، will lead to important interaction between these tunnels. In this paper، using 3D numerical modeling of line 1 twin tunnels of Tabriz urban railway، excavation stability of these tunnels، using critical strain of Sakurai، have been studied. Also displacement pattern of lining in both twin tunnels (Sahand & Sabalan) have been investigated. In next step، effect of excavation of these tunnels on the subsidence of surface and adjacent buildings، using Cramer criteria and finite difference method (FLAC 3D)، have been studied. For the purpose of study of the interaction effects between these tunnels، forces and moments that act on the segmental lining of each tunnel and their safety factor have been verified. Eventually، stability of pillar that lies between two tunnels، have also been evaluated. The results show that: 1-twin tunnels of Tabriz metro will be stable during excavation. 2-Surface subsidence due to excavation of these tunnels will have no important effect on existing structures. 3-Safety factors varies between 5-10 on the different positions of segmental lining. 4- Pillar that lies between twin tunnels will be stable

Nowadays، subways and urban tunnels are one of the most important infrastructures of public transportation network in big cities. Since the new tunnel projects should be constructed in under ground in populated urban areas، construction and implementation of this underground systems may cause damages to utilities، surface and subsurface structures. In this article، because of the importance of the issue of crossing the old urban areas and the need to reduce damages as much as possible، the distance between Stations N. 11 and 12 of Line 1 of Tabriz Subway that contains of old and traditional structure with old buildings of low strength has been studied. Due to existence of Cultural Heritage buildings in this distance، the study of settlements was performed using three different methods including Peck’s empirical method، Laganatan & Pollus’ analytical method and finite element method of numerical methods (using PlAXIS3D Tunnel software). Finally، the results of aforementioned methods were compared. The results show that the settlement values ​​obtained from the numerical model are more than the settlement values obtained from Peck’s empirical method and Laganatan & Pollus’ analytical method. Also، since the settlement values obtained from the numerical model are more than the allowable settlement values in urban and residential areas، it is needed to perform the necessary controlling strategies in this distance in order to make the excavating system able to cross this distance safely.

One of the most important issues in mechanized tunneling specially in the urban areas is selection of the suitable boring machine. Geological and geotechnical conditions، soil type and variations، underground water level، site location and urban conditions are important parameters that influence the machine type and excavation method in the urban areas. In this paper in addition to the mentioned parameters the performance of mechanized machines and guidelines of the machine selection is assessed for Tehran Metro Line7 tunnel (East-West part). East-West tunnel is located between Takhti Stadium، A7 station in the east of Tehran and N7 station in Navvab-Safavi highway. The tunnel boring diameter is 9. 15 m and tunnel length is 12360 m. According to geological studies the ground soil is divided into four types based on the soil type، grain size distribution and geotechnical conditions. The divided types cover wide range of the soil from clay to sand. Also more than 60 % of the tunnel length is located blow the underground water level. Various parameters such as tunnel route، soil type، site conditions، underground water level، project time schedule and different shield machines performance and limitations have been considered for machine selection. Among the different shield machines in the soft ground، EPB type shield machine is chosen as a suitable tunnel boring machine for the project. In addition to required auxiliary equipment، lower excavation costs and higher performance، the EPB type machine is a suitable option in comparison to other shield machines based on the project soil type. The EPB shield has priority over other shield types due to range of applications and excavation in different mode (open، EPB، slurry); therefore this type is recommended for the project.

Various underground spaces such as tunnels are constructed in urban areas for different purposes. These spaces are often located in soil media near to ground surface. In EPB tunneling, the face pressure (P) and backfill grouting pressure (G) are the most important factors to prevent the surface settlement. The 7th line of Tehran subway project is excavated by EPB machine. In this paper four section of 7th line tunnel are selected and the influence of face pressure on surface settlement are investigated numerically by PLAXIS Tunnel software. In two section of tunnel the results of numerical models are verified by monitoring instruments. In next two sections of tunnel, four status of face pressure: P=P0 (estimated initial pressure), P=1.5P0, P=2P0 and P=4P0 and for each state, five status of backfill grouting pressure: G=0, G=P, G=P+0.5 bar, G=P+1 bar and G=P+2 bar are considered and surface settlement are analyzed. Results show that an increase of %400 for face pressure lead to a decrease of maximum 5 mm in surface settlement. So in this project the influence of face pressure is trivial but the influence of backfill grouting pressure is more significant.