(사)한국터널지하공간학회
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- E-ISSN2287-4747
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ISSN : 2233-8292
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e-SubmissionVol.19 No.3
Abstract
Tunnelling in urban areas, it is essential to understand existing structure-tunnel interactive behavior. Serviced structures in the city are supported by pile foundation, since they are certainly effected due to tunnelling. In this research, thus, pile load distribution and ground behavior due to tunnelling below grouped pile were investigated using laboratory model test. Grouped pile foundations were considered as 2, 3 row pile and offsets (between pile tip and tunnel crown: 0.5D, 1.0D and 1.5D for generalization to tunnel diameter, D means tunnel diameter). Soil in the tank for laboratory model test was formed by loose sand (relative density: Dr = 30%) and strain gauges were attached to the pile inner shaft to estimate distribution of axial force. Also, settlements of grouped pile and adjacent ground surface depending on the offsets were measured by LVDT and Dial gauge, respectively. Tunnelling-induced deformation of underground was measured by close range photogrammetric technique. Numerical analysis was conducted to analyze and compare with results from laboratory model test and close range photogrammetry. For expression of tunnel excavation, the concept of volume loss was applied in this study, it was 1.5%. As a result from this study, far offset, the smaller reduction of pile axial load and was appeared trend of settlement was similar among them. Particulary, ratio of pile load and settlement reduction were larger when the offset is from 0.5D to 1.0D than from 1.0D to 1.5D.
Abstract
In order to solve the traffic congest and environmental issues, small-cross section tunnel for small car only is increasing, but there is not standard for installation of disaster prevention facility. In this study, in order to investigate the behavioral characteristics of thermal environment and smoke in a small cross section tunnels with a large port exhaust ventilation system, the A86, the U-Smartway and the Seobu moterawy tunnel, Temperature and CO concentration in case of fire according to cross sectional area, heat release rate and exhaust air flow rate were analyzed by numerical analysis and the results were as follows. As the cross-sectional area of the tunnel decreases, the temperature of the fire zone increases and the rate of temperature rise is not significantly affected by heat release rate. However, there is a difference depending on the change of the exhaust air flow rate. In the case of applying the exhaust air flow rate Q3+2.5Ar of the large port exhaust ventilation system, the temperature of the fire zone was 7.1 times for A86 (Ar = 25.3 m2) and 5.4 time for U-smartway (Ar = 37.32 m2) by Seobu moterway tunnel (Ar = 46.67 m2). The CO concentration of fire zone also showed the same tendency. The A86 tunnels were 10.7 times and the U-Smartways were 9.5 times more than the Seobu moterway. Therefore, in the case of a small section tunnel, the thermal environment and noxious gas concentration due to the reduction of the cross-sectional area are expected to increase significantly more than the cross-sectional reduction rate.
Abstract
In the current work, a series of three-dimensional finite element analysis was carried out to understand the behaviour of pile when the tunnel passes through the lower part of a single pile or group piles. At the current study, the numerical analysis analysed the results regarding the ground reinforcement condition between the tunnel and pile foundation. In the numerical modelling, several key issues, such as the pile settlements, the axial pile forces, the shear stresses and the total displacements near the tunnel have been thoroughly analysed. The pile head settlements of the single pile with the maximum level of reinforcement decreased by about 16% compared to the pile without ground reinforcement. Furthermore, the maximum axial force of the single pile with the maximum level of ground reinforcement experienced a 30% reduction compared to the pile without reinforcement. It has been found that the angle of ground reinforcement in the transverse direction affects the pile behaviour more so than the length of the ground reinforcement in the longitudinal direction. On the other hand, in the case of the pile group with the reinforced pile cap, the ground displacement near the pile tip appears to be similar to the corresponding ground displacement without reinforcement. However, it was found that the pile cap near the pile head greatly restrained the pile head movement and hence the axial pile force increased by about 2.5 times near the pile top compared to the piles in other analysis conditions. The behaviour of the single pile and group piles, depending on the amount of ground reinforcement, has been extensively examined and analysed by considering the key features in great details.
Abstract
The amount of ventilation required in making the tunnel ventilation plan is an important factor for determining the capacity of the ventilation system. The amount of pollutant emission for each type of vehicle (basic emission amount for the design of ventilation volume) for estimating the required ventilation amount is based on the ‘Standard for Allowing the Emission for the car manufacturing’, proposed by Ministry of Environment. However, in 2013, the Ministry of Environment announced the ‘Regulations on the calculation method of total emissions from vehicles’ as a regulation for calculating the pollutants emitted from vehicles. In this regulation, there are the ‘Emission factors for each type of vehicle’. Therefore, it is necessary to review the application of the Regulation to the estimation of the required ventilation volume for the road tunnel. In this study, the influence of the strengthened emission regulation in 2015 caused by the case of manipulation of emission volume for the diesel vehicle on the calculation of the required ventilation volume in the road tunnel has been checked. In addition, in this study, the required ventilation volume calculated according to the Standard for Allowing the Emission for the car manufacturing revised by Ministry of Environment and “Emission factors for each type of vehicle” and that calculated according to the EURO emission standard were compared for analysis. This study has implications that it provides the basic design data for calculating the reasonable ventilation capacity of the ventilation system based on the ground for calculating the required ventilation volume.
Abstract
Recently, due to the saturation of ground structures and the overpopulation of pipeline facilities requires to development of underground structures as an alternative to ground structures. Thus, mechanized tunnel construction of the shield TBM method has been increasing in order to prevent vibration and noise problems in construction of the NATM tunnel for the urban infrastructure construction. Tunnel construction plan for the tunnel line should be formed in a sharp curve to avoid building foundation and underground structures and it is inevitable to develop a shield TBM technology that suits the sharp curve tunnel construction. Therefore, this study is about the structural stability technology of the articulation jack, shield jack and skin plate for the shield TBM thrust in case of the mechanized tunnel construction that is a straight and sharp curve line. The construction case study and shield TBM operation principle are examined and analyzed by the theoretical approach. The torque of the cutter head, the thrust of the articulation jack and the shield jack, the amount of over cutting for curve is important respectively in shield TBM construction of straight and sharp curve line. In addition, it is very important to secure the stability of the skin plate structure to ensure the safety of the inside worker. This study examines the general structure and construction of the equipment, experimental simulation was carried out through numerical analysis to examine the main factors and structural stability of the skin plate structure. The structural stability of the skin plate was evaluated and optimizes the shape by comparing the loads of the articulation jack by selecting the virtual soil to be applied in a straight and sharp curve line construction. Since the present structure and operation method of the shield TBM type in domestic constructions are very similar, this study will help to develop the localized shield TBM technology for the new equipment and the vulnerability and stability review.
Abstract
In current, there has not been the evaluation model for the optimum design of the multi-utility tunnel by considering urban type and size, the function of surrounding road and feasibility analyses with respect to construction method, and arrangement of accommodation facilities inside multi-utility tunnel. Thus, in this study, we developed the evaluation model for the optimum design of the multi-utility tunnel before and after the decision of the multi-utility tunnel installation. In this paper, we have selected the Deming cycle which is used in various fields among several decision methods for optimizing the design. For the purpose of reflecting the various factors in the design of the multi-utility tunnel, 11 higher indicators were set up to lead to more detailed approaches. In addition, based on the “Plan-Do-Check-Action (PDCA)” circulation method, we can realize the installation of the multi-utility tunnel and design more efficiently through the first phase for conception and the second phase for optimization, and develop the program for the evaluation model accordingly.
Abstract
The uncertain existence and insufficient information of underground structures, such as pipe lines and cable tunnels, is causing many problems related to route plan, design, construction of new underground structures. The theoretical equations that is able to predict the location, size, and direction of underground structures through electric field analysis are suggested at the previous study (Ryu., 2015). Three field tests were performed for predicting the location, size, and direction of underground structures and the existence and size of sink-hole. Prediction results were reflected at the design and follow-up measures were performed.
Abstract
Bentonite swells when it comes into contact with water and makes it a viscous fluid. Thus it is widely used in civil engineering works for waterproofing. Utilizing the properties of bentonite, the slurry shield TBM supports excavated face with pressurized slurry as well as transporting excavated muck. When bentonite is in contact with seawater, due to the change of double layer thickness, its expandability and viscosity are lowered. This may cause problems for excavation stability and muck discharge due to the increase of sea water inflow when Slurry TBM is used under sea water conditions. In this study, the change of slurry condition caused by the inflow of sea water during tunnel excavation with Slurry TBM was investigated and a slurry management guideline was proposed. For this purpose, a laboratory test was carried out based on the slurry management criterions applied in the field, and a method applicable to the field where sea water is affected has been proposed.
Abstract
Wear prediction of TBM disc cutters is a very important issue for hard rock TBMs as number of cutter head intervention. In this regard, some model such as NTNU, Gehring model, CSM models have been used to predict disc cutter wear and intervention interval. There are some deficiencies in these models. This paper developed a new test method for wear prediction for TBM disc cutter and proposed a new abrasion index. In this regard, different abrasivity indices along with their testing methods are explained. A comparative study is performed to develop the predictability of different cutter life evaluation methods and index. The evaluation of the new methods proposed in this paper shows a very good agreement with the actual cutter life and intervention interval length. The proposed tester and index can be easily used to predict the intervention interval length and cutter wear evaluation in both planning and construction stages of a TBM tunneling project.
Abstract
The collapse accidents during a open ground excavation in urban areas not only lead to human injuries and material damages in the construction site, but also lead to road sinks and damages to the adjacent facilities due to settlement of ground around the construction site. Therefore, during a open ground excavation in the urban areas, it is necessary to thoroughly prepare for prevention of collapse accidents, and consider whole construction stage such as planning, design and construction. In this study, the priorities to be managed mainly were obtained in order to prevent collapse accidents during a open ground excavation. After analyzing results from past accidents cases for open ground excavations, priorities were evaluated regarding collapse-inducing elements using the Delphi technique which is a decision-making method by consensus among experts. As a result, insufficient groundwater treatment, bad geotechnical investigation and instability on construction, etc. were obtained as priorities for prevention of collapse accidents.
Abstract
Underground structures that have recently become larger are required to be stable not only during normal times but also during earthquakes. Especially, it is very important to maintain the stability of the subsea tunnels during the earthquake. The objective of this paper is to verify the effectiveness of the flexible segment, which is one of the breakthrough facilities to maintain the stability of the subsea tunnel during the earthquake using the shaking table test. Another goal of this paper is to propose the optimum position of the flexible segment through 3D dynamic numerical analysis based on the verified results from shaking table tests. The 1g shaking table test considering the similarity ratio (1:100) to the cross section of the selected artificial subsea tunnel was carried out considering the Geongju and Artificial seismic waves, longitudinal and lateral wave, and with/without flexible segments eight times or more. As a result of the shaking table test, it was confirmed that the flexible segment is effective in improving the seismic performance of the undersea tunnel in all the experimental results. In addition, 3D dynamic numerical analysis was performed to select the optimum position of the flexible segment which is effective for improving seismic performance. As a result, it was confirmed that the seismic acceleration is attenuated when the flexible segment is installed adjacent to the branch section in subsea tunnel.
Abstract
The transverse ventilation system, commonly applied to urban tunnel, is necessary to be distributed with airflow uniformly. In this study, we developed a program that can optimize the opening ratio of ports to ensure ventilation performance of design criteria through a uniform airflow distribution even though ventilation interval becomes longer. And program’s prediction performance was verified by comparison with TUNVEN DUCT program. For comparison, Semi-transverse ventilation system was applied. Both programs predicted a similar port size and air flow distribution, and the variation range of the calculated values was 11.71% and 1.36%, respectively. This program is very useful for port optimization design of transverse and semitransverse ventilation system, because it is possible to analyze various tunnel lengths and supply/exhaust port installation conditions.
Abstract
In this study, drainage systems were proposed to drain the leakage of groundwater in the existing underground concrete structures. Drainage technology consists of drainage board, wire mesh, fixed nail, and mortar with mineral. For the purpose of increasing the construction speed, the drainage board and wire mesh were attached on the surface of cement concrete using the air nailer and fixed nail. The mortar with 30% of blast furnace slag was sprayed on the drainage board and wire mesh using the spray mortar equipment. The field test construction was carried out in a conventional concrete lining tunnel and concrete retaining wall for performance verification of the drainage system in the field. There was no problem with performance degradation in the drainage system after three years. The bond strength tests were performed on the sprayed mortar at 14 days and about 3 years after field test construction. In case of attaching the wire mesh on the drainage board, the bond strengths of the sprayed mortar were 1.04 MPa at 14 days and 1.46 MPa about 3 years. In case of the drainage board without the wire mesh, the bond strengths of the sprayed mortar were 1.13 MPa at 14 days and 0.89 MPa, less than 1 MPa of bond strength criteria, about 3 years.
Abstract
A spray-applied waterproofing membrane which consists of polymers has a relatively higher constructability and adhesion than the conventional sheet-type waterproofing materials. And the spray-applied waterproofing membrane generally shows a waterproofing ability as a composite structure with shotcrete or concrete lining. Because its purpose is waterproofing at the structure, structural effects were not well reported than waterproofing abilities. In this study, structural effects of the membrane-attached concrete lining were evaluated using 3-point bending test by the numerical method. From the analysis, a load-displacement behavior of the concrete lining and fracturing energy after yielding were compared with various conditions. Consequently, concrete lining with spray-applied waterproofing membrane shows more higher flexural strength and fracturing energy than the single-layer concrete lining.