• Journal of the Korean Geotechnical Society
• /
• v.23 no.11
• /
• pp.87-98
• /
• 2007

For the quick rehabilitation of a fire-damaged tunnel structure, it is the most important procedure to investigate the fire-induced damaged zone rapidly. This study aims to propose a new drilling resistance testing method by which mechanical properties of tunnel concrete lining altered by high temperature can be estimated easily and continuously. Especially, it alms to derive the relationships to estimate mechanical properties of mortar and concrete materials from drilling parameters. To obtain the optimum testing condition, a series of drilling resistance tests were carried out for mortar specimens. When the rotation per minute of drill bit, tile penetration rate and the bit diameter were 1,300 rpm, 1.40 mm/sec, and 10 mm respectively, the deviation of measured drilling resistance forces was minimal. Under the optimum testing condition, the relationships between drilling resistance and mechanical properties of mortar specimens were shown to be very favorable. The concept of replacing a mean value of resistance farces measured during drilling with the resistance energy was proposed to consider the effects of randomly distributed aggregates inside a concrete material on drilling resistance. When the concept was applied to concrete materials, a favorable relationship between actual compressive strength and drilling resistance energy was also successfully derived.

• 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 Korean Tunnelling and Underground Space Association
• /
• v.7 no.4
• /
• pp.343-352
• /
• 2005

In this study, the existing methods proposed to estimate the relaxed load due to a tunnel excavation are compared and analyzed. Also a new approach, by which the stress relaxed zone around an excavated tunnel periphery can be systematically estimated, was suggested for the design of 2-arch tunnel lining. To this end, local factors of safety are calculated from the redistributed stresses after the excavation of a tunnel. The height of the relaxed load is inferred based on the assumption that the stress relaxed zone might coincide with the region corresponding to the local safety factor of 2.0 or 3.0. The new approach proposed in this study has the advantage of estimating the height of the relaxed load independent of the shape of a tunnel and the ground conditions, Since the height of the relaxed load is estimated according to the local factor of safety, which is a relatively clear criterion, the designer's subjectivity involved in the design of concrete tunnel lining might be reduced.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.5 no.1
• /
• pp.23-31
• /
• 2003

Since the mid of 1990, permanent shotcrete tunnel linings such as Single-shell and NMT have been constructed in many countries for reducing the construction time and lowing construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of permanent shotcrete linings, high performance shotcrete having high strength, high durability and better pumpability has to be developed in advance as an integral component. This paper presents the idea and first experimental attempts to increase early strength and bond strength of wet-mixed Steel Fiber Reinforced Shotcrete (SFRS) in spring water condition. In order to increase early behavior of SFRS, a new approach using high-early strength cement with alkali-free liquid accelerator has been investigated. From the test results, wet-mix SFRS with high-early strength cement and alkali-free accelerator exhibited excellent early compressive strength improvement compared to the ordinary portland cement and good bond strength even under spring water condition.

• Journal of the Korean Geotechnical Society
• /
• v.28 no.8
• /
• pp.79-88
• /
• 2012

In this study, the tunnel loads acting on the concrete lining are analyzed by comparing three methods - Terzaghi table, Terzaghi formula and Ground-Lining Interaction (G.L.I) model. The tunnel loads are analyzed by FLAC 2D. And the G.L.I model is analyzed under various rock mass ratings, tunnel depths (20~80m) and in-situ stress ratios ($K_0$=0.5~2.0). Terzaghi's method can be applied only to weathered rocks and soils, and cannot reflect the effect of various tunnel depths and in-situ stress ratio. The proposed G.L.I model can not only be applied to various ground conditions, but also relieves the tunnel loads by up to 30%.

• Tunnel and Underground Space
• /
• v.28 no.6
• /
• pp.620-634
• /
• 2018

The NTR(New Tubular Roof) method was used to secure the stability of the tunnel and minimize the subsidence of the road. The tunnel was constructed at about 7.5 meters deep below the highway. with a width of about 21 meters. Following the NTR method, 13 steel pipes with a diameter of 2.3 meters were digged and pushed in longitudinally along the tunnel profile and cut out sides of pipes to connect to adjacent pipes, then filled the inside of pipes and the connected space between pipes with concrete to complete the lining of the tunnel to be excavated. As the steel pipes were digged in sequentially, the area of relaxation was connected to each other and behaves like a gradually widening tunnel. When the steel pipes were digged in to the widest points of the tunnel, the settlement rate of the road surface was increasing to the maximum as 2.2 mm and the total settlement until the lining construction was approximately 7.7 mm. After that, by excavating a tunnel inside the pre-installed lining, an additional settlement of about 4.3 mm was occurred, resulting in the total settlement of about 11.8 mm after completing of tunnel construction.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.2
• /
• pp.149-158
• /
• 2011

Utilization of the fiber reinforced polymer (FRP) material has been increased as an alternative in a bid to supplement the problems with general construction materials such as long-term problems corrosion, etc. However, there are still many problems in using a linear-shaped FRP material for a tunnel lining structure which has arch-shape in general. In this study, the loading tests for the FRP-concrete composite member was carried out to evaluate their applicability as a tunnel reinforcement material, which are based on the results from preliminary numerical studies for identifying the behavioral characteristics of FRP-concrete composite member. Moreover, numerical analysis under the same condition as applied in the loading tests was again conducted for analysis of mechanical behavior of the composite member. As a result of the load test and numerical analysis, it appears that the FRP-concrete composite member is greatly subject to shear movement caused by bending tension acting on the interface between two constituent members.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.1
• /
• pp.37-45
• /
• 2009

In this study, experiments of development and application of 50 MPa high-performance concrete are performed for large dimensional tunnel linings. In order to produce 50MPa high-performance concrete, eight optimal mixtures replacing with fly ash and ground granulated blast furnace slag up to 50 percent of type I Portland cement were selected then tests for mechanical properties and simple adiabatic temperature rise tests were carried out. And in order to assess the quantitative characteristics of heat of hydrations of developed mixtures, three mixtures that the type I Portland cement (OPC) and each one mixture of binary and ternary mixtures (BS30, F15S35) were reselected, then the adiabatic temperature rise tests and mock-up tests were performed. Consequently, the comparisons between the results of mock-up tests and finite element analysis can be enhanced the reliability of analyzing routines of thermal behaviours of the developed high-performance concrete.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6A
• /
• pp.873-880
• /
• 2008

When checking the state of deterioration or damage structures, regular visual inspection has very important role. At this point, a visual inspection is performed mainly by sketch or photography with a camera of inspectors. If that happens, it takes a lot of effort and time to inspect appearance damages. The purpose of this study is to develop the automatic recognition system for a more efficient and effective inspection of appearance damages. In the process, the image processing technology and the data management & analysis system for damage recognition are mainly developed and applied. This automatic recognition system enables inspectors or clients to obtain correct data that can recognize a damage, such as, crack, water leakage, efflorescence, delamination (peeling), spalling, etc. In addition, this study takes aim at the effect of secure safety, functional maintenance and extension of design lifetime according to build up continuous and systematic data management system.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.151-154
• /
• 1999

The lining concrete of water tunnel is a structure that is constructed to prevent from corroding of the rock around tunnel and reduce the deterioration of geology by flowing water, and to improve the durability of tunnel, which must not only economy, stability but also satisfy the engeneering properties of concrete. This is an experimental study to analyze th usability of fly in the tunnel lining concrete. For this purpose, after select the mix proportion of plain concrete and concrete using fly ash(the replacement of 15 and 30% by weight of cement) to satisfy slump, air content and compressive strength through the mix design, the test of slump, setting time, compressive strength, tensile strength, drying shrinkage and adiabatic temperature rise was performed. According to test results, it was found that FA 15 concrete was more effective than the others to reduce drying shrinkage as well satisfy other engineering properties.