• Geomechanics and Engineering
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• v.34 no.2
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• pp.115-124
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• 2023

By conducting three-dimensional simulation with consideration of small-strain characteristics of soil stiffness, the effects of excavation geometry and tunnel cover to diameter ratio on deformation mechanisms of an existing tunnel located either at a side of basement or directly underneath the basement were systematically studied. Field measurements were used to verify the numerical model and model parameters. For basement excavated at a side of an existing tunnel, the maximum settlement and horizontal displacement of the tunnel are always observed at the tunnel springline closer to basement and tunnel crown, respectively, regardless of basement geometry. By increasing basement length and width by five times, the maximum movements of tunnel located at the side of basement and directly underneath the basement increase by 450% and 186%, respectively. Obviously, tunnel movements are more sensitive to basement length rather than basement width. For basement excavated at a side of an existing tunnel, tunnel movements at basement centerline become stable when basement length reaches 10 H_e (i.e., final excavation depth). Moreover, tunnel heaves due to overlying basement excavation become stable when the normalized basement length (L/H_e) is larger than 8.0. As tunnel cover to diameter ratio varies from 2.5 to 3.0, the maximum heave and tensile strain of tunnel due to overlying basement excavation decrease by up to 41.0% and 44.5%, respectively. If basement length is less than 8 H_e, the assumption of plane strain condition of basement-tunnel interaction grossly overestimates tunnel movements, and ignores tensile strain of tunnel along its longitudinal direction. Thus, three-dimensional numerical analyses are required to obtain a reasonable estimation of tunnel responses due to adjacent and overlying basement excavations in clay.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.56-65
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• 2006

As portions(28m) of the designed tunnel was crossing the abandoned tunnel, methods for safe construction were demanded. The level of the abandoned tunnel and the designed tunnel was almost same and each tunnel was crossing at an angle of about 40 degrees. Therefore the abandoned tunnel would adversely affect the stability of the designed tunnel. Some sections of the abandoned tunnel passes through the designed tunnel wall were fully filled with tunneling spoil and cement milk grouting to increase tunnelling stability. By checking physical properties of grouting cores drilled at the cross section of the designed tunnel and the abandoned tunnel, the quality of material filled in the abandoned tunnel was confirmed. Also the stability of the designed tunnel was checked by the monitoring during excavation of the tunnel.

• Geomechanics and Engineering
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• v.22 no.6
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• pp.497-507
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• 2020

This paper presents the results of a three-dimensional numerical investigation into the effect of new tunnel construction on structural performance of existing tunnel lining. A three-dimensional finite difference model, capable of modelling the tunnel construction process, was adopted to perform a parametric study on the spatial variation of new tunnel location with respect to the existing tunnel with emphasis on the plan crossing angle of the new tunnel with respect to the existing tunnel and the vertical elevation of the new tunnel with respect to the existing one. The results of the analyses were arranged so that the effect of new tunnel construction on the lining member forces and stresses of the existing tunnel can be identified. The results indicate that when a new tunnel underpasses an existing tunnel, the new tunnel construction imposes greater impact on the existing tunnel lining when the two tunnels cross at an acute angle. Also shown are that the critical plan crossing angle of the new tunnel that would impose greater impact on the existing tunnel depends on the relative vertical location of the new tunnel with respect to the existing one, and that the overpassing new tunnel construction scenario is more critical than the underpassing scenario in view of the existing tunnel lining stability. Practical implications of the findings are discussed.

• Tunnel and Underground Space
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• v.17 no.6
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• pp.453-463
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• 2007

Terzaghi's tunnel pressure theory is generally used to estimate primary design pressures on tunnel support for shield and urban NATM tunnels until now. A trial is made in this paper to investigate the interaction between the ground deformation behavior and Terzaghi's tunnel pressure, which assumes pound's limit (or critical) state, by considering results of 'Terzaghi's tunnel pressure theory. two-dimensional reduced-scale model tunnel tests and nonlinear numerical analysis based on strain softening modeling. A full understanding between tunnel pressure and ground deformation behavior under the tunnel excavation and an effective utilization of this interaction lead to an economical tunnel support design and a safe construction of tunnel.

• Geomechanics and Engineering
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• v.10 no.4
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• pp.471-526
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• 2016

In order to investigate water flow characteristics after inrushing in process of karst tunnel excavation, numerical simulations for five case studies of water inrush from the tunnel floor are carried out by using the FLUENT software on the background of Qiyueshan high risk karst tunnel. Firstly, the velocity-distance curves and pressure-distance curves are drawn by selecting a series of probing lines in a plane. Then, the variation characteristics of velocity and pressure are analyzed and the respective optimized escape routes are made. Finally, water flow characteristics after inrushing from the tunnel floor are discussed and summarized by comparing case studies under the conditions of different water-inrush positions and excavation situations. The results show that: (1) Tunnel constructors should first move to the tunnel side wall and then escape quickly when water inrush happens. (2) Tunnel constructors must not stay at the intersection area of the cross passage and tunnels when escaping. (3) When water inrush from floor happens in the left tunnel, if tunnel constructors meet the cross passage during escaping, they should pass through it rapidly, turn to the right tunnel and run to the entrance. (4) When water inrush from floor happens in the left tunnel, if there is not enough time to escape, tunnel constructors can run to the trolley and other equipment in the vicinity of the right tunnel working face. In addition, some rescuing equipment can be set up at the high location of the cross passage. (5) When water inrush from floor happens in the cross passage, tunnel constructors should move to the tunnel side wall quickly, turn to the tunnel without water inrush and run to the entrance. (6) When water inrush from floor happens in the cross passage, if there is not enough time to escape, tunnel constructors can run to the trolley and other equipment near by the left or the right tunnel working face. The results are of important practical significance and engineering value to ensure the safety of tunnel construction.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.112-119
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• 2005

In road tunnel, in order to prevents an accident and minimize the damage of an accident in the case of fire, safety facilities and equipments are integral parts. The type and amount of safety facilities are based on tunnel type and length, traffic flow rate, etc. Therefore many countries use a tunnel classification system that categories tunnel into groups, and specifies the necessary emergency equipment for each group. In this study, for the purpose of classifying tunnel based on tunnel ist investigated the domestic and foreign standards and regulations for safety of road tunnel. As a results, we suggest the method of classification of tunnel by traffic performance, tunnel grade, the volume of traffic, fraction of HGV, rules or regulations for transports of dangerous good through tunnel.

• Geomechanics and Engineering
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• v.6 no.5
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• pp.455-467
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• 2014

As the traffic increased, the original capacity of the tunnel has been unable to meet the needs, so it must be expanded. Based on the features of tunnel, the intermittent trough method must be supposed for tunnel enlarging. Under the situation on the buried deep of the tunnel, it could be used the reasonable arch axis model to descript the past covered rock pressure for mechanism calculating of self-bearing arch. Then establish the three-arch combination effectible model for the analysis which is relied on the tunneling enlarging to Chongqing Yu-Zhou tunnel. It has determined the proper width for the intermittent trough in shallow buried tunnel enlarging.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.373-389
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• 2019

It is important to study the problem of durability for tunnel structures. As a main influence on the durability of tunnel structures, carbonation-induced corrosion is studied. For the complicated environment of tunnel structures, based on the data samples from real engineering examples, the intelligent method (genetic programming) is used to construct the service life prediction model of tunnel structures. Based on the model, the prediction of service life for tunnel structures in carbonation environments is studied. Using the data samples from some tunnel engineering examples in China under carbonation environment, the proposed method is verified. In addition, the performance of the proposed prediction model is compared with that of the artificial neural network method. Finally, the effect of two main controlling parameters, the population size and sample size, on the performance of the prediction model by genetic programming is analyzed in detail.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.77-87
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• 2019

In this paper, the interaction between two neighboring tunnel has been investigated using PFC2D. For this purpose, firstly calibration of PFC was performed using Brazilian experimental test. Secondly, various configuration of two neighboring tunnel was prepared and tested by biaxial test. The maximum and minimum principle stresses were 0.2 and 30 MPa respectively. The modeling results show that in most cases, the tensile cracks are dominant mode of cracks that occurred in the model. With increasing the diameter of internal circle, number of cracks decreases in rock pillar also number of total cracks decreases in the model. The rock pillar was heavily broken when its width was too small. In fixed quarter size of tunnel, the crack initiation stress decreases with increasing the central tunnel diameter. In fixed central tunnel size, the crack initiation stress decreases with increasing the quarter size of tunnel.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.576-582
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• 2013

Typical highway infrastructure systems include roadway pavement, drainage systems, tunneling, and other hardware components such as guardrails, traffic signs, and lighting. Tunnels in a highway system have provided significant advantages to overcoming various natural challenges including crossing underneath bodies of water or through mountainous areas. While only a few tunnel failure cases have been reported, the failure rate is likely to increase as these assets age and because agencies have not emphasized tunneling asset management. A tunnel system undergoes a deterioration life cycle pattern that is similar to other infrastructure systems. There are very few agencies in the United States implementing comprehensive tunnel asset management programs. While current tunnel asset management programs focus on inspection, maintenance, and operation safety, there is an increasing need for the development of a comprehensive life cycle tunnel asset management program. This paper describes a conceptual framework for a comprehensive tunnel asset management program. The framework consists of three basic phases including a strategic plan, a tactical plan, and an operational plan to provide better information to the decision makers. The strategic plan is a basic long term approach of tunnel asset management. The tactical plan determines specific objectives and the operational plan actually applies asset management objectives in practice. The information includes operational condition, structural condition, efficiency of the system, emergency response, and life cycle cost analysis for tunnel capital improvement project planning.