نشریه مهندسی تونل و فضاهای زیرزمینی
سال دهم شماره 3 (پاییز 1400)

Tunnels have been built in the neighborhood as a result of the growth of the transportation industry. These tunnels are built crosswise or parallel to each other, not level. The distribution of stress around the tunnels and the behavior of the ground are affected by the location of these tunnels relative to each other and the drilling process. Accidents can occur due to a lack of understanding of the behavior of adjacent structures. As a result, understanding these structures is critical. The goal of this research is to fully investigate the impact of parallel tunnel drilling on inductive forces on the first tunnel's maintenance cover and subsidence in order to better understand the behavior of nearby structures. These analyses were carried out in this paper using the plaxis 2D finite element method. According to the findings, the amount of surface subsidence decreases as the horizontal distance between the two tunnels increases, while the amount of surface subsidence increases as the vertical distance between the tunnels increases. Increasing the depth of the second tunnel has also increased the inductive load and bending moment on the first tunnel's maintenance cover. Increasing the vertical distance between the two tunnels on the desired outlets causes more changes than increasing the horizontal distance.

With the development and growth of the population in big cities; The need to use public transportation facilities such as the metro is growing. Given the importance of the urban transportation network, it is very important to pay attention to the health control of underground structures against static and dynamic loads. As Iran is one of the seismic countries in the world, in recent years it has witnessed devastating earthquakes and has caused heavy damage. According to previous studies, underground structures are more safe against earthquakes. Because surface structures are connected to the ground only on the floor and lower surface. If the underground structures are in full conflict with the surrounding environment and are more resistant to earthquake loads. However, given that most subways are built on shallow urban soils, there have been reports of severe damage to these underground spaces from earthquake loads. For this reason, identifying damage and controlling the health of underground spaces, especially subways, is very important. In this research, due to the uncertainty in the ground parameters and also the lack of accurate forecast of the drilling route, 3DEC software (when dealing with rock layers) along with PLAXIS3D2020 software has been used for static and dynamic analysis of Mashhad Metro Line 2 tunnel. In addition, in order to control the health of the structure (Mashhad Metro Line 2), wavelet transform (WT) methods have been used. For this purpose, the received signal was called by dynamic analysis and using the wavelet conversion toolbox in MATLAB software, damage areas were identified in the model (around the concrete cover and side borders), which obviously can be identified using the maintenance system. Properly prevented the collapse of the underground structure in the identified areas.

Today, the importance of using Underground structures to protect vital and sensitive national infrastructure such as urban train tunnels, strategic item storage centers, urban underground facilities, shelters, as well as military uses is not hidden from anyone. One of these important loads in terms of intensity and time is impact and seismic loading. Due to the fact that the environment around the underground structures is rock and soil environment, so it is necessary to achieve a good result in reducing the effect of mechanical waves on these spaces, to ensure sufficient reduction of the environment. One of these important loads in terms of intensity and time is impact and seismic loading. On the other hand, natural phenomena such as gas explosion or fire can also be easily incorporated into the structure. These are enough reasons to pay more attention to the science of rebuilding structures against different loads on them. The importance of protecting these spaces increases when they have strategic applications. Therefore, in locating and designing them, it should be noted that they must have sufficient resistance to impact loading In order to achieve a plan that by using the properties of the environment including such spaces, the effect of the impact transmitted in the environment on the underground space can be reduced. Therefore, in the past few years, this software has attracted the attention of many researchers. Finite element modeling and analysis was performed with the commercial software package ABAQUS. The package was selected due to its diverse library of material behavior models and ease of Explicit/Implicit solution procedures. In this paper, impact loading on Underground structures is numerically modeled using the Coupled-Eulerian-Lagrangian (CEL) method in the ABAQUS software. In this regard, modeling of single-layer, two-layer and three-layer soil arrangement, as well as a combination of soil and stone layers, has been done in ABAQUS finite element software. The maximum pressure due to impact load has been compared in different models and finally, by comparing the results of the models used in this study, it shows that the arrangement of the layer in the soils is effective in reducing the maximum pressure due to impact load, So that the maximum amount of shock wave damping is achieved when the rock layer with the highest degree of weathering, or sandy soil (similar to type 2 soil in Regulation TM5-855) is in the closest position to the desired underground space.

Recently, most underground structures are mechanized using excavation shields. Moreover, one of the major challenges in underground structures is the ground deformation. So, the analysis of this mechanism is necessary for safety purposes and project design. One of the effective parameters in the ground displacement is the geometry of the excavation shield. Since the pipes are connected to the excavation shield, the initial stress relaxation and displacement are not allowed. In this regard, having a cone excavation shield can solve this problem. In this research the effect of excavation shield conicality on the ground is investigated. The Plaxis finite element software is utilized for numerical modeling. Moreover, in order to validation, the results are verified with the field data and analytical analysis. Furthermore, the effect of stress on the pipeline is also investigated in this research. Finally, it is found that the relationship between conical excavation shield and ground surface displacement is linear. The load on the pipeline almost doubles with increasing the percentage of conicality of the shield from 0.3% to 0.9%. One of the most important applications of this research is the possibility of controlling the ground movement with respect to the effective parameters.

With the increasing expansion of urban environments, the creation and development of intra-city transportation systems in order to reduce traffic, pollution and reduce the costs of intra-city traffic is essential. Considering that an important part of the construction cost of the metro is related to the excavation and maintenance of tunnels. Therefore, one of the most important decisions in the construction of subway tunnels is the excavation method in alluvial and fall environments. Tunnel excavation by TBM-EPB machine is a fast, powerful and maintenance method compared to other excavation methods in soft soils and fall areas. One of the most important factors in preventing the face pressure from falling during excavation in soft and alluvial fields is estimating the optimal face pressure of the excavation machine in each excavation stage (different kilometers). Because the high or low face pressure of the excavation machine leads to increased costs, loss of life, high hardness and also leads to delays in the completion of the project. In this paper, due to the uncertainty in geotechnical parameters and the sensitivity of urban tunnels, the issue has been studied from a probabilistic perspective. For this purpose, first for 50 different numerical modeling modes of Tabriz Metro Line 2 using PLAXIS3D2020 software and then Monte Carlo simulation method has been used to generate random numbers and assign appropriate probabilistic distributions. Then, using the Gray Wolf meta-heuristic algorithm (GWO), the face pressure of the TBM-EPB machine was estimated using the prediction relation. Finally, in order to evaluate and validate the relationship, the statistical indicators of square correlation coefficient (R2), variance inclusion (VAF), mean absolute error percentage (MAPE), root mean square error (RMSE) and mean square error (MSE) were used. Is. According to the model validation, the relationship created by the gray wolf algorithm is very close to the reality of the problem and it can be used to continue the route in other similar areas.