• Tunnel and Underground Space
• /
• v.14 no.5
• /
• pp.345-352
• /
• 2004

In a shotcrete support system, the cooperation of the ground and the shotcrete lining makes it possible to transfer the shear stress to the shotcrete lining, which is dedicated to form a stable structure. In this study, a homogeneous model ground with constant strength was produced by using gypsum and the tunnel was excavated with a top heading method under the definite initial stress. During the excavation, the stress in the ground around the tunnel and the deformation of shotcrete lining were measured, The tensile stress was generated in tangential direction in the ground near the tunnel and in the shotcrete lining due to tunnel excavation. This shows the unified behavior of the ground and shotcrete lining, which is the most typical characteristic of the shotcrete support. As a result, the rates of in-situ stress during the excavation at a top boundary line was 9% and at top arch heading 15%. It was 48% right after excavating the heading and 94% before cutting the bench.

• Journal of the Korean GEO-environmental Society
• /
• v.18 no.1
• /
• pp.5-12
• /
• 2017

The damage of the tunnel lining on the cold regions can be represented by cracks and leaks caused by freezing of ground water. However, domestically, the relevant construction guidelines are not provided so far. Thus, in this research, the mechanical behavior and thermal conductivity of designated tunnel area are measured using instrumentation system installed in the lining concrete inside tunnels in order to analysis their behavior with regard to temperature variations. Previous research mainly focused on the effect of temperature on the tunnel lining based on the air and initial ground temperature at urban regions. Thus, this study analyzes effects of air temperature and initial ground temperature of designated tunnel area at the cold regions. The temperature of the groundwater at the backfill of the tunnel lining are analyzed to evaluate the heating element. Numerical analyses are performed to evaluate the heating element with regard to the various initial ground temperatures.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.9 no.1
• /
• pp.1-18
• /
• 2007

This study is about an arrangement method of trapezoidal pre-cast segment lining that can be applied in shield tunnel construction. Trapezoidal segment lining is formed by assembling tapered pre-cast concrete segments taking advantage of the tapered shape of pre-cast segments upon delivery on site. By calculating tapering of the segments manufactured in single type and rotating the segments when putting them together, a variety of tunnel alignments can be arranged in the most efficient way. Once the design criteria and tunnel alignment (straight or curved) is analyzed, the sequence of assembling trapezoidal segments in compliance with tunnel alignment will be computed. On site an operator can utilize the softwareto automatically determine sequential arrangement of trapezoidal segments. When the actual arrangement of segmental lining is different from the computed output, the operator can input the actually measured values to coincide the computerized calculation with the real status of assembly. Then the adjustment will be the basis of subsequent arrangement of segments, thus the continuity of work can be guaranteed.

• Journal of the Korea Concrete Institute
• /
• v.19 no.2
• /
• pp.189-197
• /
• 2007

Concrete tunnel lining must be designed to having the fireproof performance because the lining are sometimes exposed to very high temperature due to traffic accident. Such fire temperature may cause explosion of concrete, or collapse of tunnel structure. The purpose of this study is to obtain the fundamental fireproof behavior of fire resistance-engineered cementitious composites(FR-ECC) under fire temperature in order to use the fire protection material in tunnel lining system. The present study conducted the experiment to simulate fire temperature by employing 2 types of FR-ECC and investigated experimentally the explosion and cracks in heated surface of these FR-ECC. Employed temperature curve were hydro carbon(HC, ECl) criterion, which are severe in various criterion of fire temperature. The numerical analysis is carried out the nonlinear transient heat flow analysis and verified against the experimental data. The complex features of behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. By the use of analytical model, the concrete tunnel subjected to fire loads were analyzed and discussed. With comparison of current concrete materials and FR-ECC, the experimental and analytical results of FR-ECC shows the better fire resistance performance than the other.

• Fire Science and Engineering
• /
• v.23 no.6
• /
• pp.66-74
• /
• 2009

When a fire occurs, the concrete structure's strength decreases by the increasing temperature under the fire in certain condition of constant load. And, the ratio of the axial force is changed by such decreased strength so that the structure is deformed. In this research, considering such case, we have conducted an actual fire test for the concrete lining with constant loading condition and various fire conditions. The specimen adopts the shape condition for small practical specimen defined by the EFNARC and we used 24MPa, 40MPa and 50MPa to analyze the thermal properties by the strength. The ratio of loading is imposed by a certain loading condition based on 20% and 40% of the sectional stress in concrete and MHC Fire is selected to realize the thermal impact of the concrete by rapid increasing temperature. As the result of the experiment, in the same ratio of loading, the 50MPa specimen shows more cracks and spalling as time goes on. The area damaged by the fire, according to the functional criteria of the concrete lining under the fire in ITA, does not satisfy with the standard in lack of 50mm depth from the heating surface at total 200mm lining.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.817-820
• /
• 2000

Existence of void or delamination inside building foundation or tunneling lining can cause serious problems in structural safety. Therefore, 0probing of such voids in architectural and civil structures is an important process in evaluating the overall integrity of the structures. In this study, the radar method has been examined in its use in detecting voids inside concrete specimens. The dimensions of the specimens are 1,000 mm(width) $\times$ 600 mm (height) $\times$ 140 mm (thickness). A void is embedded inside concrete specimens with the dimensions of 200 mm(width) $\times$ 600 mm (height) $\times$ 50 mm (thickness). Concrete cover depth of 30 mm, 60 mm is studied for comparison. In both cases, the voids is located with 1 GHz antenna.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.373-378
• /
• 2003

The cement-based composites have relatively low tensile strength and toughness. The fiber addition is one of the most important ways of increasing the toughness of concrete. The steel fibers have been used conventionally in the shotcrete of tunnel lining. Recently, the structural synthetic fibers were developed and used frequently in some actual tunnel shotcreting in foreign countries. Now types of synthetic fibers have been developed in this study. The purpose of this study is to explore the strength and toughness characteristic of the concrete reinforced with synthetic fibers developed in this study. The result were compared with those of steel fiber reinforced concrete. It is seen that the performance of synthetic fiber reinforced concrete is good as much as that of steel fiber reinforced concrete, while the synthetic fibers have advantages in corrsion resistance and economy.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.2 no.3
• /
• pp.37-45
• /
• 2000

In recent years two reflection methods, i.e. GPR and seismic Impact-Echo, are usually performed to obtain the information about tunnel lining structures composed of concrete lining, shotcrete, water barrier, and voids at the back of lining. However, they do not lead to a desirable resolution sufficient for the inspection of tunnel safety, due to many problems of interest including primarily (1) inner thin layers of lining structure itself in comparison with the wavelength of source wavelets, (2) dominant unwanted surface wave arrivals, (3) inadequate measuring strategy. In this sense, seismic physical modeling is a useful tool, with the use of the full information about the known physical model, to handle such problems, especially to study problems of wave propagation in such fine structures that are not amenable to theory and field works as well. Thus, this paper deals with various results of seismic physical modeling to enable to show a possibility of detecting the inner layer boundaries of tunnel lining structures. To this end, a physical model analogous to a lining structure was built up, measured and processed in the same way as performed in regular reflection surveys. The evaluated seismic section gives a clear picture of the lining structure, that will open up more consistent direction of research into the development of an efficient measuring and processing technology.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.5
• /
• pp.717-733
• /
• 2019

In this study, lining thickness distribution and its behind state (particularly, its void state) were analyzed using the GPR survey data performed on three currently operating NATM tunnels. Results of GPR analysis showed that void areas were mostly detected between concrete lining and primary support, particularly, near the crown of the tunnels. The lining thickness in the left-hand side of the tunnel was different from that of the right-hand side by 8.6~253.5 mm when measured in transverse direction. It was also found that longitudinal cracks were prevailed in the area lining thickness was sharply changed. Longitudinal thickness distribution at the crown was also studied and tested by performing 3 goodness-of-fit tests in order to find the most suitable thickness distribution. Normal distribution (or similar distribution) fit most suitably to the measured data if the measured average thickness was larger than designed one; Gamma and/or Inverse Gauss distribution fit to the measured data reasonably well if the measured average thickness was less than the designed value of thickness. Since actual lining thickness can be a potential index when assessing the state and safety of the unreinforced NATM tunnel lining, measuring of the lining thickness with GPR survey might be needed rather than assuming the thickness is always constant and same with the designed value.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.149-152
• /
• 2008

FBG sensor system is applied to the concrete lining structure in Taegu subway. Near the structure, the power cable tunnel construction started. We wanted to measure the deformation of the structure due to the construction by the FBG sensor. The applied sensor has the gauge length of 1 meter to overcome the inhomogeneity of the concrete material with enough length. In order to fix tightly to the structure, the partially stripped parts of the sensor glued to the package and slip phenomenon between fiber and acrylate jacket was prevented. Prestrain of the sensor was imposed by controlling the two fixed points with bolts and nuts in order to measure compressive strain as well as tensile strain. The behavior of subway lining structure could be monitored very well