There are many researches and contributions on stress analysis of tunnel’ s roof and wall. But there is not enough research on invert stress analysis, especially in soft grounds. In this paper it has been tried to introduce an analytical model for prediction and calculation of invert up-lift pressure in soil and very poor quality rock mass. Figure 1 shows the problem under tunnel’ s structures. When the pressure is high tunnel designer must be considered an invert structure for control of instability under tunnel lining. The pressure can be occurred by swelling process in some rocks and soils with high value clay content when there is a variation in moisture. But this research has been focused on invert up-lift pressure just by field stress and geomechanics conditions. Stress concentration and pore pressure have been considered in the equilibrium limit analysis and Mohr-Columb failure criterion has been applied as a linear well-known formulation for soils and very jointed rock masses behavior.

In order to have an economic design to reduce uplift pressure in weighted concrete dams, so many methods have been proposed that the most important include: adding horizontal apron, cutoffs in upstream and downstream of the dam and weep hole installation in downstream or proper place between the two cutoffs. These implementations also reduce the exit gradient. The effects of these parameters are the main subject of this study. This study focuses on Yusef Kand Mahabad diversion dam, by study on the dam and its simulation in Seep/W software, effect of number of weep hole on uplift pressure, proper location of weep holes on stilling basin and also the length of the dam cutoffs. Simulation was studied on uplift pressure and exit hydraulic gradient in key points of diversion dam and the overall stability of the dam. In this study, it was observed that creating primary upstream cutoff with 8 m length decreases uplifting force about 63% and decrease exit gradient 79% than the case without cutoff. Creating a weep hole in the stilling basin decreases uplifting force 8% and decrease exit gradient 74% than the case without weep hole. Results demonstrate that suitable location of weep holes can reduce uplift pressure and so the diversion dam design can be safe and economical.

Cracked concrete arch dam’s behavior due to moderate earthquake magnitude and water pressure variation was investigated. Plain concrete was used to cast the dam’s models with 45 Mpa design strength. A shake table has been planned, manufactured, and built to create a dynamic testing facility. The experimental work was included testing of four scaled-down concrete arch dams’ models, which is divided into two groups, each group contains two different degrees of curvature models. An artificial crack was made at the center of the dam’s body. The extended finite element method (XFEM) is outlined in order to address the numerical predicate for the propagation of a crack. The results showed that a good behavior of all arch dams under moderate earthquake intensity. The arch dam with a higher degree of curvature was recorded 17.8% and 16.2% low displacement at Z and X-direction respectively, stress evaluation and crack propagation in comparison with the arch dam owns the lowest degree of curvature. Hence, increasing the degree of curvature led to raising the stability of the dam, earthquake resistance, less displacement, and less growth of tensile cracks.

Seepage flow modeling beneath hydraulic structures on permeable materials is an essential issue that must be considered before construction processes. Because of no detailed studies, followed by inappropriate design some problems such as foundation erosion, seepage and water escape and structure settlement may be occurring. If we couldn’t overcome these problems in designing process, we can utilize a series of auxiliary actions. Some actions for eliminating the piping and reducing the uplift pressure and hydraulic gradient are construction of horizontal apron, cut-off walls and also weep holes. Hence, in this study the effect of the weep hole on uplift pressure and hydraulic gradient has been investigated. For this purpose, the governing equation of flow through porous media has been solved for different setups, by the numerical method of Control Volume. All calculations have been done by the simple and powerful Excel Spreadsheet tools. Results show that, the application of weep hole reduces the uplift pressure and hydraulic gradient. Installation of a weep hole on stilling basin could reduce the cut-off wall depth and this cause a noticeable reduction of project costs. By moving weep hole toward the downstream of stilling basin and getting away from dam toe, its positive impact will be reduced.

Recent studies regarding dam failure show that most dam failures are due to unsuitable conditions of foundation and insufficiencies depth of bed rock. Seepage, uplift pressure and piping phenomenon under the foundation of dam cause disastrous failures in dams that exit gradient is an important criterion for safety against piping. Therefore, finding methods will be to reduce seepage flow, exit gradient and uplift pressure will be very important. In this study, ANSYS software is employed for analysis and modeling water flow in foundation dam. This study determines the flow characteristics (flow rate and exit gradient) and quantities of uplift pressure in an impervious dam with sheet pile. Extensive analyses were performed for different condition, including dam width and sheet pile depth. The results have been presented in simple charts. These simple charts allow designer to predict seepage problems and perform an optimum design in short time.

The ground reaction curve (GRC) is a vital component of the convergence-confinement method, which possesses many applications in the underground space designs. It defines a relation between the tunnel wall deformations and the ground pressure acting on the tunnel walls. Generally, GRC includes descending and ascending branches. According to many researchers, the descending branch trend for the ground pressure stops after the critical deformation, and thus the ground pressure on the support system increases due to the formation of a loosening zone and an ascending branch, and finally, the creation of an ultimate pressure on the support system. In this work, two relations are proposed to determine the ultimate ground pressure acting on a circular tunnel in a continuous medium. It is assumed that the rock mass obeys the elastic perfectly plastic model with a cohesionless behavior in the broken zone. This is accomplished by incorporating the Duncan-Fama solution and the two models of Yanssen-Kotter and Caquot rigid plastic. The ground pressure obtained by the Caquot model shows a better correlation with the Goel-Jethwa equation compared with the Yanssen-Kotter solution.

It is clear that the estimation and investigation of the aerodynamic peak pressure due to the passage of two high-speed cross trains intersecting in the tunnel is important because of its effects on passenger safety and tunnel structure. In this study, transient aerodynamic peak pressure of two high-speed ETR500 cross-train models in tunnel with the speed of 170 km/h is investigated. A high-speed rotary scaled model (HRSM) test setup is used to perform experiments and the aerodynamic peak caused by the high-speed train moving into the tunnel is obtained on the standing train in the tunnel. Also, a numerical simulation of the test is done using computational fluid dynamics using the sliding mesh technique, and the results are compared with the results obtained from the scaled test as well as the relevant data in the literature. The results are presented based on the non-dimensional parameters. The results of the study provide a validation field for the future studies.

The penetration rate is a crucial parameter in the performance of Earth Pressure Balance (EPB) Tunnel Boring Machines (TBMs), which is used to assess the time and cost of completing a project. However, so far, no model has been presented to predict the penetration rate in soft soils, leading engineers to rely on approximate estimations based on similar projects. This results in significant inaccuracies in project completion time. In this article, statistical analysis has been conducted using performance data from EPB TBMs worldwide to examine the correlation between the penetration rate and its influencing factors. The parameters discussed include tunnel diameter, face pressure, undrained shear strength, unconfined compressive strength, head opening ratio, and standard penetration number. Based on the data analysis, three parameters, namely head opening ratio, unconfined compressive strength, and standard penetration number, have been identified as significant influencing factors. This article provides useful relationships for estimating the penetration rate with determination coefficients ranging from 68% to 72%. Considering the absence of an accurate performance prediction model for soft ground TBMs, the results of this study assist tunnel project engineers in the initial stages of the project by enabling better evaluation of performance parameters, time, and cost requirements.

Nowadays, earth pressure balance tunnel boring machines (EPB-TBMs) are favorably used in urban mechanized tunneling projects. The availability of these machines is rather low, so their performance, time planning, maintenance scheduling and cost control may need further improvements. The reliability, availability and maintainability (RAM) of any machine could be analyzed by evaluating the actual performance of that machine or system and thereby minimizing maintenance costs. In current research work, RAM analysis of the electrical system of the EPB-TBM in line 1 of Tabriz metro in Iran is performed. For this investigation, failure and repair data were collected during about 26 months of machine operation. Statistical tests including trend and serial correlation tests indicated that the data are independently distributed, consequently the statistical technique was used for modeling. The data analysis also revealed that the time between failures (TBFs) and time to repairs (TTRs) data fit to the Lognormal (3P) and Gamma (3P) distributions, respectively. Reliability analysis showed that there is approximately 80.1% chance for the electrical system of TBM machine to be operational for 15 h without any failure. Moreover, the maintainability curve indicated that most of the failures have been repaired in less than 1 hour and that it is more likely that 80% of these failures would be repaired in 1.88h. Also the availability of electrical system of this machine is found to be equal to 97.8%.

Estimation Face pressure and Thrust force of TBM are one of the basic requirements in mechanized boring. In case of incorrect estimation, there is a possibility of face instability, shrinkage of shield and machine stuck, which leads to costs increasing and prolonged completion time of project. The Kani Sib tunnel consist of two sections of rock and alluvium. Due to the presence of underground water, low mechanics rock parameters and high overburden on alluvial section, this section is one of the most dangerous parts of the tunnel. For that reason, in this paper, estimation of face pressure and trust strength in mechanized excavation of the alluvial section has been studied. At first, in order to do this, required face pressure for maintenance was calculated by analytical method and verified by numerical method. After checking the accuracy of selected pressure, the pressure on the shield and thrust force, which includes force applied from face, shield fraction force, disc cutter force and tension force of the shield, was determined.