نشریه مهندسی تونل و فضاهای زیرزمینی
سال دهم شماره 2 (تابستان 1400)

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.‎

Structures with different shapes or materials show different behaviors against shock waves, and a correct understanding of the structure's performance against these waves can be useful and effective in choosing the appropriate shape of materials. In this study, the amount of energy reduction of impulsive mechanical waves on the attenuator elements with different materials and different thicknesses has been investigated. Attenuator elements that have been considered in the world today and have shown good results have been modeled. The soil model employed was chosen from the U.S. Army TM 5-855-1 soil classification as Type 5, i.e., highly saturated clay.With the increasing development of software and hardware facilities in recent decades, the use of finite element software in solving engineering science problems has made significant progress. Like ABAQUS, FLAC and ANSYS software. For example, ABAQUS software compared to other similar finite element software, due to its explicit and implicit solution procedures, has advanced and diverse behavioral models for different materials such as metals, rubber, concrete, soil, stone, fluids and ability to quick development of models with complex geometry. Therefore, in the past few years, this software has attracted the attention of many researchers.One of the important results in this study is effect of Geofoam in reducing by 60% and Auxetic sandwich panel in reducing by 50% of the emitted wave energy in the soil. One of the innovative aspects of this project is the study of the effect of new materials. Another aspect of innovation compared to previous studies is the study of all these effects is in a composite environment, such as the earth, which is composed of different components such as rock and soil. Each of these components, due to their parameters and properties, have an effect on the propagation of mechanical waves and cause differences.

Roadheader machine is one of those machines that have high drilling capability in rocks with low to medium strength. Hence they are widely used in underground excavations. Estimating the performance of roadheader machine is one of the main and important issues in estimating the approximate project completion time as well as project costs. Therefore, the purpose of this paper is to propose intelligent forecasting models for estimating the performance of roadheader machine by two intelligent methods (the firefly algorithm (FA) and the Teaching-learning based optimization algorithm (TLBO)) and using a database (a case study). Is. In these models, the Schmidt hammer rebound values and the rock quality degree (RQD) are used as input parameters and the cutting rate of the roadheader is used as the output parameter. Finally, to evaluate the accuracy of the models and modeling, the indices of square correlation coefficient (R2), variance account for (VAF), root mean square error (RMSE) and mean square error (MSE) have been used. The results indicated that the two models have strong potentials to estimate roadheader performance with high degrees of accuracy and robustness.

Earth Pressure Balance Machines (EPB) were used to excavate the Tabriz metro line 2. A critical section of the tunnel Has modeled in this study. The model has been verified by the monitoring data using the installed instruments on site. In addition, some crucial operational parameters of the Earth Pressure Balance Tunnel Boring Machine (EPBM) have also been studied to determine their effect on ground deformation and subsidence during tunnel excavation. Tunneling in shallow urban areas and on soft ground is always associated with risks that can have unpleasant consequences if ignored. Tunnel excavation removes a mass of soil and rock, leading to significant changes in strength around them, and causing the Earth to move. The tunnel has been excavated in a shallow soil environment; these effects will transfer to the ground. An earth pressure balance shield (EPB) is one of the most suitable methods to control the pressure in the tunnel front, decreasing the surface subsidence by controlling this pressure. The study applied three-dimensional (3D) numerical modeling to study the effects of TBM-EPB operating parameters on the deformation and subsidence of soft soils using FlAC3D software. According to the obtained numerical results, it seems that these slurry injection pressures did not have a significant effect on the improvement of stresses. The study investigated the influence of overburden pressure, cohesion, density, and diameter on injection pressure. The results indicate that decreasing or increasing the injection pressure in environments with different parameters has little effect on vertical displacement. To investigate how geomechanical factors of the environment influence deformation of the Earth's surface, models were constructed by keeping all the parameters constant according to which, with increasing cohesion and internal friction angle, the rate of subsidence decreases. While increasing the specific gravity of the soil, the amount of vertical displacements increases.

Today, the use of tunnel boring machines to drill long tunnels under different geological conditions has become widespread. On the other hand, in tunnel projects, especially subway projects, the situation of tunnel boring due to time consuming and high cost, determines the main strategy of the project. In this research, using a systemic approach, the dynamic relationship of the factor affected by tunnel boring machines in tunnel projects has been investigated and analyzed.The system in this model includes three subsystems for the production of precast concrete parts, tunnel boring machine and the process of discharging drilling materials, in this model, the data obtained from two TBM machines in a period of 3 years have been used.The simulation results show the effect of tunnel boring character from factors such as drilling diameter, production rate of precast concrete parts, discharge rate of drilling pool and various problems. Finally, the model is validated and sensitivity analysis is performed on the model.According to the initial input numbers of the model, the quantitative results of the model indicate that if the production rate of precast concrete parts is reduced from 12 to 7 per day, tunnel boring will be completed 40 days later and If the number of shifts of tunnel boring machines changes from 2 shifts to one shift per day, the drilling time will increase from 397 days to 823 days.By changing the number of shifts from 2 to 3 tunnel boring shifts per day and increasing the number of mud trucks serviced from 55 to 75 services, the time required for tunnel boring will be reduced from 397 days to 277 days.Considering the general inclusion of the model for all tunnel boring systems, by changing each of the independent variables of the model and defining different scenarios, the best possible result can be achieved for project management and project strategies can be developed based on it.

Trenchless methods are increasingly utilized to replace the worn out pipelines or to fabricate the new pipelines. The advantage of these methods is to prevent the vast amount of excavations and also to reduce damages to the adjacent facilities. The settlement of the surface area is one of the greatest concerns in trenchless methods. The pipe splitting method is a sophisticated 3D activity. In the present work, numerical modeling of pipe splitting strategy considering the expander transmission, the surrounded soil response and also geotechnical parameters have been regarded. The simulation has been carried out with Abaqus software considering the pipe spilling experimental test case profound analysis. In this research, not only have the embedded depth, the replaced pipe diameter, the type of soil, the pipe splitting machine type been evaluated, but also the blade orientation has been assessed. The results show that the bullet have more horizontal deformation and the clampbuster has more vertical deformation. The orientation of the blade determines whether the deformations are horizontal or vertical, and increasing the depth of the buried pipe causes a nonlinear decrease in surface deformations. With an increase of 400 mm in depth, the deformations have been reduced by 20 mm. As the diameter of the pipe increases, the general pattern of deformations is the same, but the values are different. Surface deformation in sand is greater than in clay. The values for sand and clay are 36 and 12 mm, respectively. The amount of lateral deformation of the sand around the pipe was also doubled.