جستجوی مقالات مرتبط با کلیدواژه "حفاری مکانیزه" در نشریات گروه "عمران"

One of the most critical problems of mechanized tunnelling is the abrasion of cutting tools. Soil abrasivity significantly reduces drilling efficiency and increases the operating costs of urban tunnels. There are extensive studies on abrasivity of rocks. However, limited studies have been performed on the influence of soil particle size distribution on tunnelling machine cutting tools. Despite the wide range of methods and devices for measuring soil abrasivity, so far, no standard and comprehensive method for measuring soil abrasivity have been presented. In this study, considering the effect of some effective parameters on the abrasion of cutting tools, a new laboratory machine to determine soil abrasivity was constructed. Then, using 8 different types of soil granulation, the effect of soil particle size distribution and density on cutting tool abrasion was studied. Also, using the Talbot curve, the abrasion values ​​of cutting tools in different particle sizes were compared. The results showed that the highest values ​​of cutting tools abrasion occur in soils with particle sizes according to the Talbot equation. As the soil granulation curve moves away from the Talbot curve, abrasivity decreases. Also, the maximum abrasion of cutting tools occurs in the amount of fine aggregate of 10% with an average abrasion percentage of 27.3%. By reducing the fine aggregate to values lower than 10%, the soil structure is disturbed and as a result, the average abrasion percentage of cutting tools decreases from 27.3% in soil with 10% fine aggregate to 2.37% in soil without fine aggregate. Also, by increasing soil density from 1.6 to 1.8, the average abrasion percentage of cutting tools increases from 8.1% to 31.4%.

 In mechanized tunneling of soft grounds with boulders, several types of cutting tools are used on the cutter head of the machine. The main cutting tools used in this condition are rippers, disks or a combination of them. In the tunnel of the eastern part of the Mashhad urban railway line 3 project, due to fine grain layers the tunnel section, the main tools used were the rippers. The discs were used only in the cutter head gauge. The addition of a gravel layer containing boulders in the tunnel section has reduced the durability of the rippers and increased the specific excavation energy up to 25%. In order to increase durability, NFM designed rippers were replaced with heavy rippers. In addition, various alloys have been investigated by test and error method. Changes in dimensions and alloy increased the durability if the tools up to 37%. By replacing the NFM designed rippers with heavy rippers, the performance of the rippers have increased from 183 meters to 250 meters. The result of tool replacement in the eastern part of Mashhad urban railway line 3 (about 10 km from the route) shows that the consumption of cutting tools in the boulder area was 10 times the area before the collision with the boulder. In general, 280 tools have been replaced in the investigated boulder area (about 1.7 km), which has resulted in saving about 60 billion rials by using heavy rippers instead of NFM rippers.

In this study, in order to investigate and evaluate the performance of the EPB TBM, the parameters of progress rate and foam consumption for ground improvement have been used. To evaluate the performance of EPB tunnel boring machine in this research, drilling data were used from 4 databases namely Qom metro line one project, Shiraz metro line two project (east and west tunnel), Isfahan metro line two project and Isfahan metro line one project which have been EPB TBM excavated. Based on this database, models based on statistical techniques including regression analysis (simple regression, linear multivariate (MLR) and nonlinear (MNLR) regressions) and support vector machine least squares (LS-SVM) algorithm were developed to evaluate the foam consumption and the advance rate. Then, in order to study more accurately and better the experimental and intelligent models presented to predict the foam consumption and the advance rate, statistical indicators such as the coefficient of determination (R2), the statistical values ​​of the root mean square of the normalized error (NRMSE) and error variance (VAF) for each developed model were calculated using the test data set. Comparison of the calculated values of R2, VAF and NRMSE for the models developed to predict the foam consumption and the advance rate showed that the proposed model based on the LS-SVM algorithm has remarkable accuracy compared to other models, in predicting the amount of foam consumption and the advance rate of the EPB tunnel boring machine. The values of R2, VAF and NRMSE indices for the developed model in the prediction of the amount of foam consumption are 0.945, 94.356 and 0.237 respectively, and in the prediction of the advance rate are equal to 0.741, 74.071 and 0.149, respectively.  Due to the high accuracy of predicting the amount of foam consumption (Qt) and the advance rate (AR), the models which are developed on the LS-SVM algorithm basis, can play a significant role as applied models in the mechanized drilling industry.

More recently, the demand has been raised for application of segmental tunnel lining in long and deep tunnels in rock beds and also shallow tunnels in soft ground, particularly in urban areas. From technical and economic aspects, proper dimensioning and connecting of the segmental linings have always attracted the interest of many designers in the field of tunneling. The guiding rods are placed in the horizontal joints of the segment to make the segment easier to install and to provide shear strength at the joint. In this article, first, the types of joints in tunnel segments are studied and how the connections in these joints work are discussed. Next, the performance of the guiding rod is examined and the operation of the guide rod in the tunnel is investigated. For this purpose, the tunnel is first modeled with the real geotechnical conditions of the ground from the metro terminal to Abuzar town station in plaxis2D software and the values ​​of axial and shear forces in the tunnel structure are obtained. Based on the outputs of the plaxis2D model, the amount of shear strength borne by the cross section of the segment and the guide rod is presented. Abacus software is used to analyze the behavior of the guide bar and the output of this model shows that the solid and hollow guiding rods have linear behavior and the hollow guiding rod can also be used for this part of the tunnel route, which can effectively reduce construction costs.

Due to the expansion of urban spaces and as well as the lack of necessary spaces for intra-city transportation, the need for subway construction in urban areas is more acute than ever. In order to build a subway,it is necessary to build underground structures such as tunnels and several stations.Today, one of the most important construction issues in metro projects is deciding on the sequence of tunnel or station construction. Obviously, proper allocation of resources to different departments requires careful technical and economic consideration of different options and special attention to aspects related to work planning. In this research, two methods of tunnel or station execution sequence in two general cases of full and empty passage have been investigated.Furthermore, considering that each of the above methods requires the adoption of measures to prevent possible problems and delays, these arrangements have been stated in each case.Finally, the economic comparison of the sequence of tunnel construction and the station in the seven metro lines of Tehran has been studied.Studies show that the construction of the tunnel before the construction of the station is more economical than the construction of the station before the construction of the tunnel. And this can save a lot of money for a metropolis like Tehran, which needs to build a large number of subway lines and stations. Also, familiarity with the costs, obstacles and problems of each of the above methods can be useful in deciding on the appropriate method and contract to start a rail project.

LCPC test is one of the most common methods to assess the abrasivity of rock particles and soil samples. Regarding the lack of a standard testing procedure to determine the abrasivity of soils, the test has become very popular in recent decades. The effect of clay on soil abrasivity was investigated with LCPC tests. Different mixtures of crushed silica grains and clay particles were used in the testing program. Moreover, measuring the consumed power of the electric motor of the testing device, the consumed energy of each LCPC test was calculated. Different moisture contents and stress levels were also applied in the tests. The results showed that the LCPC abrasivity coefficient decreases with increasing moisture content. However, after a certain water content level, abrasivity shows an increasing trend with moisture. abrasivity is nearly zero in pure clay samples. The results showed that minimum abrasivity values are obtained when the moisture content is in the range between plastic limit and liquid limit. Applied stress on the soil samples, increases the soil abrasivity. However, increasing the clay content of the tested samples decreases the rate of LAC increasing trends with the applied stress levels. In the pure clay samples, no correlation was obtained between the applied stress levels and LAC values. The results showed that the clay part alone does not have a sensible abrasivity. However, its mixtures with coarse grains have a considerable effect on the abrasive behavior of tested samples especially when the applied water contents and stress levels change.

In this paper, measured settlements of Tabriz Urban Railway line 2 (TUR2) are presented. TUR2 with a length of about 22 km will connect the eastern part of the city to its western part. The process of excavating TUR2 has begun since 2015 using earth pressure balanced (EPB) TBM with a cutting-wheel diameter of 9.49 m and a steel shield with an external diameter of 9.46 m in front and 9.44 m at the tail. For the lining of the tunnel, 350 mm-thick precast concrete segments with a length of 1.5 m are installed just behind the shield. The data have been recorded during the construction of the tunnel from west-shaft to station-02 (S02). The distance between west-shaft and S02, which has been investigated here, is about 2000 m. In this route, based on conducted studies,the ground mainly consists of sand and gravel (SM) containing minor portion of fine-grained soil (ML). Thus, in general, the ground condition could be assumed to be non-cohesive at this site. The TUR2 tunnel is entirely under water table varying from 14 to 22 m. The data analyzed and discussed throughout this paper have been recorded at 180 green-field surface locations (pins) between west-shaft and S02. Settlement measurements are back-analyzed using Gaussian empirical predictions both in longitudinal and transversal directions. In addition, volume loss has been calculated using final maximum surface settlements. Subsequently, observed and calculated settlement curves have been compared. In addition to settlements, face pressure and tail void grout injection pressure have been recorded during the excavation process of TUR2, as presented in this paper. Jancsecz and Stainer presented an empirical formula for determination of face pressure to investigate the efficiency of the analytical methods in comparison with field data. Then, the development of settlements during shield passage and probable correlation between volume loss and face pressure was investigated. Observations show that a vast majority of the settlements measured at the ground surface falls in the range of allowable values.

Qom Subway line A project has been excavated by an Earth Pressure Balance (EPB) machine. New Excavation Method has been introduced which is based on controlled core-face Tunnel, indeed Controlled Deformation Rocks and Soils (ADECO-RS) in Tunnel. Numerical Simulations are used to Predict Surface Settlement for the Qom tunnel by TBM-EPB with Approach ADECO-RS and without Considering it. The longitudinal and transverse and Contour surface settlements obtained by numerical analyses are compared with Each other. The obtained numerical results for Excavation with TBM-EPB have been confirmed by the monitoring data using the installed instruments on site.

In this study, the Flac3D software has been employed for carrying out 3D numerical modeling of Control settlement. In addition, the Mohr-Coulomb criterion has been considered for geo-mechanical behavior of soil material surrounding the tunnel. the results of numerical models have been verified by the data obtained from monitoring instruments installed in the site.

The numerical results have shown that the maximum transverse surface settlement of Excavation by TBM-EPB with Approach ADECO-RS is around 50% of the maximum surface settlement of the Excavation by TBM-EPB, In addition longitudinal Profiles shown that maximum surface settlement Excavation by TBM-EPB with Approach ADECO-RS occurred about 15m behind face of the tunnel, leads to a decrease of 7.5m in the surface settlement without Approach ADECO-RS. The results have shown control core-face leads to control surface settlement and the Approach ADECO-RS can be used for Control of surface settlement trough induced by tunneling in the similar ground and excavation conditions as Qom subway tunnels.

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.

Nowadays, the tunnels based on the public’s needs may be built in unfavorable geological conditions. In most of these situations, the use of mechanized excavation technology is unavoidable to improve the performance and safety. Mechanized tunneling in difficult conditions with many risks, including the fault zones, water inflow and squeezing that tunneling operations could stop for a long time. It is very important to predict and assess the hazards because of the large volume of investment in such projects. In this study, it was tried to investigate the stability and convergence of environment and water inflow in seven section of the second part of the Emamzadeh Hashem (AS) tunnel using analytical and numerical methods after identification of the geological characteristics and geotechnical risks. Then, the most risky section was investigated and introduced using Fuzzy Delphi Analytical Hierarchy Process (FDAHP) and PROMETHEE methods. Thus, after selecting criteria, including the instability of the tunnel, water inflow and squeezing, the weighting of each criterion was determined using FDAHP method according to the severity, rate and probability of disaster. Finally, the most risky section of the second part of Emamzadeh Hashem (AS) tunnel was evaluated using the PROMETHEE method. Thus the H-3 section was introduced and selected as the most risky section based on geotechnical properties. The results of this study showed that a combination of multiple criteria decision making, analytical, numerical and fuzzy methods can be used to predict and evaluate the geotechnical risks and doing disaster risk reducing actions to reduce the risk.

Risk management is today known as one of the nine major project management bodies of knowledge science. An effective risk management allows decision makers to identify the project's strengths, weaknesses, and opportunities. Also, they will be ready to respond if they arise. It includes identifying, recording, ranking and recognizing of response actions and also allocation of actions to corresponding risks. An appropriate risk management of a project helps project managers in getting safe conditions for project design and implementation. Therefore, one area in which there is a necessary need for decision making is project risk management. One of the main steps in risk management is risk assessment and risk ranking, which are important parts of risk management. On the other hand, tunneling projects are now risk-prone activities in mining engineering context. Missing or incomplete risk management in tunneling projects leads to negative consequences, such as longer project time and increased costs. Due to the multiplicity of risk factors in an urban mechanized tunneling project by Earth Pressure Balance ( EPB ) machine, ranking risk is a complex convoluted procedure. So, it is necessary to use multi-criteria decision-making ( MCDM ) methods. Hence, in this paper, in order to analyze the risks of a tunneling project in Tehran Metro-Line 7, we suggest to use Technique for Order of Preference by Similarity to Ideal Solution ( TOPSIS ) method. It is a method for aggregation that compares a set of alternatives by identifying weights for each criterion. It then normalizes scores for each criterion and calculates the geometric distance between each alternative and the ideal alternative. The obtained results show that financial and human resource factors get the first high risk ranks. Furthermore, the risk of dealing with a network of aqueducts is the most well-known problems of the Tehran Metro-Line 7 project. Conducted field studies of the project and visiting the workshop site confirmed the validity of analysis.

U7 station as a backup and service center has been situated in the middle of northern-southern Tehran’s metro line 7 project, in which is being excavated using an Earth Pressure Balance (EPB) machine. In this paper, the most appropriate stabilization method for the exterior portal has been nominated, and afterward the influence of tunnel excavation with TBM upon the stability of the above-mentioned portal has also been explored in the excavating procedure onset using numerical method. As a result, soil substitution with plastic concrete which can also be categorized as one of the ground improvement methods has been selected to mitigate difficulties more effectively. In addition, optimized length of plastic concrete used to minimize tunnel face displacement and to restrict prospect instability has numerically been yielded.
In today’s world, development in infrastructure facility systems such as subways is in the public eyes more than ever. These underground openings are situated in urban and/or residential areas equated with soft soils and alluviums. Furthermore, providing a stable span for the TBM operations in station would be of great importance to avoid encountering any potential hazard like settlement, economic limitation, and even human casualties. Consequently, in EPB mechanized tunneling, fairly proper stabilization method of any station portals is found to be influential.
Methodology and Approaches: In this study, the FLAC3D software has been utilized to carry out 3D numerical modeling to investigate the influence of plastic concrete on the face stability. In addition, the Mohr-Coulomb criterion has been taken into account for geo-mechanical behavior of soil material surrounding the tunnel. Since EPB machine is not capable of producing fairly enough pressure against the tunnel face to maintain stability at the beginning of the excavation up to 1.5 meter, hence plastic concrete length required for face stability is found to be 1.5 meter. Accordingly, five plastic concrete of 2, 3, 4, 5, and 10 meter long has been inserted to a numerical model. Finally, optimized length and lateral expansion of plastic concrete have been designed generally based on result driven from numerical analysis such as tunnel crown and face displacement, raptured zones around the tunnel face and wall.
Results and Three dimensional modeling has revealed that required length to fulfill tunnel face stability is 4 meter long with respect to face displacement magnitudes and also raptured zones. Lateral expansion of plastic concrete, however, should not exceed 1 meter. Results have demonstrated that plastic concrete plays a significant role in preventing tunnel crown from enormous displacement.

In the present research، the influence of tunnel construction of the 2nd Line of Mashhad Metro in the vicinity of Sadaf hotel has been chosen as the case study. It was aimed to investigate the ground displacements and surface settlement which has been induced by tunneling with Earth Pressure Balance-Shield Tunnel Boring Machine (EPB-TBM). FLAC-3D Tunnel، as finite difference software، have been employed to model the case.

A major concern of tunnels construction is accurate prediction of ground displacement، which distort and، in severe cases، damage surface structures. Empirical Peck’s method is used commonly in many tunneling projects to predict surface settlements. Reasonable prediction by this method requires an appropriate estimation of trough width (i). This parameter can be obtained from previous case histories with similar ground conditions and excavations. A part of Shiraz subway system is constructed by twin tunnels using EPB machine. Due to the lack of relevant case histories، numerical simulations are used to predict i for the Shiraz tunnels. The longitudinal and transverse surface settlements obtained by numerical analyses are compared with empirical method. Consequently، the maximum settlement and i are predicted for a part Shiraz subway tunnels. The development of settlement profiles obtained by numerical modeling is also investigated in order to achieve the steady state condition behind the tunnel face. Methodology and Approaches: The numerical simulations are performed using PLAXIS 3D Tunnel. The tunnel construction process was done by systematic approach، in 35 phases. The empirical method suggested by Peck used to predict the transverse settlement trough. The longitudinal and transverse settlements predicted by numerical modeling are obtained during the excavation of tunnel. The development of surface settlements is studied to establish the steady state condition. The initial estimation of i is obtained by the current empirical equations. To achieve the appropriate trough width، the initial i is modified by comparison of settlement troughs obtained by empirical and numerical approaches. Results and The numerical results showed that the surface settlement directly above the tunnel face is around 45% of the maximum. Small surface settlement was induced after installation of the tunnel lining. The development of surface settlement profiles indicated that the steady state condition is reached at three times of tunnel diameter beyond the tunnel face. Comparison of the transverse surface settlement troughs indicated that trough width parameter is 1. 8 times the tunnel diameter. The current value can be used for prediction of surface settlement trough induced by tunneling in the similar ground and excavation conditions as Shiraz subway tunnels.

Prediction of TBM performance is a crucial issue in mechanized tunneling projects، since machine performance has an influence on duration and costs of the projects. Rock mass parameters have significant effects on TBM advance rate as well as influence of these parameters on each other. In order to model the effect of geological conditions on TBM downtimes using Rock Engineering Systems (RES)، a thorough database based on three long water conveyance tunnels in Iran has been developed. Advance Rate index (ARi) has been calculated using Rock Engineering Systems method and the predicting relationship between the ARi and advance rate has also been obtained using regression analysis in quadratic equation form.