نشریه مهندسی تونل و فضاهای زیرزمینی
سال دهم شماره 1 (بهار 1400)

In most projects with different Delivery systems, it is possible for claims to be made. On the other hand, faster operation of projects has led to the need to use Design-Build Delivery system. However, the implementation of projects in this way in Iran, compared to other existing methods, is new and the parties of the projects are little familiar with it; For this reason, disputes are inevitable, especially in underground projects that are complex in nature. In the present study, by examining the documents of the Tehran Tunnel and Underpass project and conducting 10 semi-structured interviews with representatives of the main pillars of the project, some claimants have been identified. After analyzing the data, which was performed using qualitative content analysis and shown through Gantt chart, it was found that sometimes the claims lead to each other during the project in a chain. Also, showing the time of occurrence of claims by five project management process groups shows that most claims occur in the executing process group, which is rooted in the initial and planning process groups.

In recent years, along with the development and expansion of cities, population growth and vehicles, the construction of underground railways by mechanized tunneling is increasing. One of the common problems of EPB-TBM mechanized tunneling in weak and unstable areas is tunnel convergence, which causes problems such as getting stuck on EPB-TBM, subsidence and damage to buildings around the tunnel in urban areas. Due to the uncertainty in the soil parameters of the region, estimating the face pressure, thrust jacks pressure and cutter head torque at different kilometers is very important to prevent over-convergence of the tunnel, getting stuck on EPB-TBM and ground subsidence. Due to the uncertainty in rock and soil, in this paper the amount of face pressure, thrust jacks force, cutter head torque and ground subsidence due to tunneling in different kilometers in the construction project of the new Istanbul airport in Turkey using numerical software, PLAXIS3D 2020, is modeled. The modeling results show that the operator can increase the face pressure by preventing getting stuck on EPB-TBM. According to the results obtained in this paper, adjusting the face pressure, thrust jacks force and cutter head torque, in addition to solving the problem of getting stuck on EPB-TBM, will reduce ground subsidence and damage structures on the ground surface.

TBM penetration rate (PR) prediction is one of the most crucial issues for project cost and time estimation, however, its prediction has remained an important challenge for engineers and investors. Results of former investigations show that there are different methods for PR prediction, including theoretical and statistical models as classic methods and neural networks, fuzzy logic systems, and neuro-fuzzy models as intelligent and new methods. Modern methods are more capable of analyzing complex and non-linear relationships in comparison with classic methods. Accordingly, the implementation of modern methods for PR prediction will lead to a more precise outcome. In this paper, the information of 14 tunnels around the world is compiled within a database. Studied parameters in this database are a combination of machine and rock mass specifications, including, normal mean thrust force (Fn), cutterhead revolution per minute (Rpm), tunnel diameter (TD), rock mass rating (RMR), rock quality designation (RQD), and uniaxial compressive strength (UCS). By analyzing and reviewing relevant results, it was determined that omission or failure to use appropriate parameters causes a poor PR prediction. These results also show that UCS and RQD are amongst the most effective parameters. Furthermore, it has been concluded that using neuro-fuzzy networks (RMSE = 0.13 m/h) provides more accurate results than neural networks (RMSE = 0.38 m/h).

In the construction of urban underground infrastructures, the passage of tunnels below the surface structures is inevitable. Prediction and control of deformations resulting from excavating, especially the ground's surface subsidence, should always be considered before drilling. For this purpose, the present study deals with the numerical analysis of the interaction between the tunnel and its adjacent buildings. In this paper, the Isfahan Metro Tunnel in the range of Azadi Square to Sheikh Koleini Station is considered and FLAC2D software is used for modeling. The characteristics of the buildings in the limited area have been considered and the effect of the width and height of the structures around the tunnel on the rate of ground subsidence caused by the tunnel excavation has been investigated. In order to validate the results, data of the subsidence instrumentation were utilized. Finally, based on the performed analysis, it was concluded that the permissible range of constructing structures around the tunnel area depends on the geometry of the structure and as the size of the structure increases, reliable limits for the construction of structures around the tunnel drilling area are reduced. As a practical result, a diagram was provided to determine the permissible range of construction around the twin tunnel based on different values of the width and height of the structure.

Lining of tunnels constructed using full-face tunnel boring machine consist of set of concrete segments which form a ring at each step of construction. In order to move forward, TBM inserts a great force through thrust jacks resting on segments. Installing a new ring requires decrease or elimination of jacking force. Therefore, the magnitude of force alternates as the construction continues which a part of this force remains as residual through the lining. This residual force may influence longitudinal flexural stiffness of the lining. On the other hand, time-dependent behavior of injected grout has a significant effect on the residual force. In this study first the time-dependent behavior of cement-based grout considering confining condition is investigated using the oedometer test and then modeling of staged tunnel construction and alternate loading of thrust jacks considering time-dependent grout setting is proposed using an analytical approach. In the end, residual force of lining after construction could be calculated. This approach is used to estimate the longitudinal residual force in No.1 line of Tabriz Subway Lining.

In this research, the effect of different tunnel depths, has been investigated from both technical and economic perspectives. Then, the optimal depth for the construction of subway tunnels has been determined according to both views. Ground surface settlement with different overburdens is the technical perspective. In this study, the allowable surface settlement limit is considered 25 mm. If the ground surface settlement is more than the allowable limit, It cannot be technically suitable for tunnel excavation. Estimation of tunnel excavation costs as well as construction costs of metro stations, along the second line of the Tabriz subway form the economic perspective of this study, to optimization of depth for subway tunnel. This research has been undertaken to identify and optimization of depth for subway tunnel excavation considering Technical and economic perspective, in the second line of the Tabriz subway as a case study. The Line 2 of Tabriz Metro consists of a double-track tunnel with a total length of 21km and 20 underground stations. The ground of the second line of the Tabriz subway is classified in two modes; The first case is, based on the type of ground and the second case is, based on the amounts of overburdens in the tunnel route. In the first case; The different layers of land along the tunnel route are classified into four general categories. In the second case; Tunnel overburdens are classified into five general categories along the tunnel route based on their height. In this research, FLAC3D V6.00.69 software was used. The amount of ground surface settlement has been investigated in 16 different models. Grounds that have more settlement than the allowable depth limit, cannot be suitable for tunnel excavation. Then, the informations related to the tunnel excavation costs as well as construction costs of metro stations, along the second line of the Tabriz subway have been calculated. Next, the optimal depth is determined from an economic perspective. Depths where the tunnel overburden is less than the diameter of the tunnel, are technically more than the allowable settlement limit, and it is not recommended that the tunnel be excavated in that spatial range of the ground. On the other hand, the investigation of this study showed that with increasing depth of tunnel, the tunnel excavation costs initially decreased, and after that when the tunnel overburdens are more than twice the diameter of the tunnel, it increases again. Also, with the increase of tunnel overburden, the construction costs of metro stations have increased. So that the construction costs of a one-story station is equal to 95 billion tomans. Meanwhile, the construction costs of a four-story station was equal to 250 billion tomans, which is much more than the previous case. Therefore, the optimal depth for the construction of tunnels and stations is when the tunnel has more overburden than the diameter of the tunnel and also less than one and a half times the diameter of the tunnel.