• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.579-582
• /
• 2005

Tunnel lining is the final support of a tunnel and reflects the results of the interaction between ground and support system. Recently it is very difficult to support and manage the tunnel because the cracks on tunnel lining cause problems in supporting and managing tunnels. Therefore the analysis of the cracks is quite strongly required. The major role played by the steel fiber occurs in the post-cracking zone, in which the fibers bridge across the cracked matrix. Because of its improved ability to bridging cracks, steel fiber reinforcement concrete(SFRC) has better crack properties than that of reinforced concrete. In this study, mechanical behaviour of a tunnel lining was examined by model tests. The model tests were carried out under various conditions taking different loading shapes, thicknesses and leakage of lining, and volume content of steel fiber. From these model test, the cracking load, the failure load, defection and cracking position and type were examined and the characteristics of deformation and failure for tunnel lining were estimated and researched.

• Earthquakes and Structures
• /
• v.15 no.6
• /
• pp.655-665
• /
• 2018

Shield tunnels are widely used throughout the world. However, their seismic performance has not been well studied. This paper focuses on the seismic response of a large scale model tunnel in compacted sand. A 9.3 m long, 3.7 m wide and 2.5 m high rigid box was filled with sand so as to simulate the sandy soil surrounding the tunnel. The setup was excited on a large-scale shake table. The model tunnel used was a 1:8 scaled model with a cross-sectional diameter of 900 mm. The effective shock absorbing layer (SAL) on the seismic response of the model tunnel was also investigated. The thickness of the tunnel lining is 60 mm. The earthquake motion recorded from the Kobe earthquake waves was used. The ground motions were scaled to have the same peak accelerations. A total of three peak accelerations were considered (i.e., 0.1 g, 0.2 g and 0.4 g). During the tests, the strain, acceleration and soil pressure on the surface of the tunnel were measured. In order to investigate the effect of shock absorbing layer on the dynamic response of the sand- tunnel system, two tunnel models were set up, one with and one without the shock absorbing layer of foam board were used. The results shows the longitudinal direction acceleration of the model tunnel with a shock absorbing layer were lower than those of model tunnel without the shock absorbing layer, Which indicates that the shock absorbing layer has a beneficial effect on the acceleration reduction. In addition, the shock absorbing layer has influence on the hoop strain and earth pressure of the model tunnel, this the effect of shock absorbing layer to the model tunnel will be discussed in the paper.

• Wind and Structures
• /
• v.7 no.3
• /
• pp.203-214
• /
• 2004

This paper describes a method for developing a multi-degree-of freedom aero-elasto-plastic model of a base-isolated mid-rise building. The horizontal stiffness of isolators is modeled by several tension springs and the vertical support is performed by air pressure from a compressor. A lead damper and a steel damper are modeled by a U-shaped lead line and an aluminum line. With this model, the frequency ratio of torsional vibration to sway vibration, and plastic displacements of isolation materials can be changed easily when needed. The results of isolation material tests and free vibration tests show that this model provides the object performance. The peak displacement factors are about 4.5 regardless of wind speed in wind tunnel tests, but their gust response factor decreases with increment of wind speed.

• Structural Engineering and Mechanics
• /
• v.45 no.3
• /
• pp.337-354
• /
• 2013

For shield TBM (Tunnel Boring Machine) tunnel lining, the segment joint is the most critical component for determining the mechanical response of the complete lining ring. To investigate the mechanical behavior of the segment joint in a water conveyance tunnel, which is different from the vehicle tunnel because of the external loads and the high internal water pressure during the tunnel's service life, full-scale joint tests were conducted. The main advantage of the joint tests over previous ones was the definiteness of the loads applied to the joints using a unique testing facility and the acquisition of the mechanical behavior of actual joints. Furthermore, based on the test results and the theoretical analysis, a mechanical model of segment joints has been proposed, which consists of all important influencing factors, including the elastic-plastic behavior of concrete, the pre-tightening force of the bolts and the deformations of all joint components, i.e., concrete blocks, bolts and cast iron panels. Finally, the proposed mechanical model of segment joints has been verified by the aforementioned full-scale joint tests.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.193-200
• /
• 1999

Since Broms and Bennermark(1967) suggested the face stability criterion based on laboratory extrusion tests and field observations, the face stability of a tunnel driven in cohesive material has been studied by several authors. And recently, more general solution for the tunnel front is given by Leca and Panet(1988). They adopted a limit state design concept to evaluate the face stability of a shallow tunnel driven into cohesionless material and showed that the calculated upper bound solution represented the actual behavior reasonably well. In this study, two factors are simultaneously considered for assessing tunnel face stability: One is the effective stress acting on the tunnel front calculated by upper bound solution; and the other is the seepage force calculated by numerical analysis under the condition of steady state ground water flow. The model tests were performed to evaluate the seepage force acting on the tunnel front and these results were compared with results of numerical analysis. Consequently, the methodology to evaluate the stability of a tunnel face including limit analysis and seepage analysis is suggested under the condition of steady state ground water flow.

• Tunnel and Underground Space
• /
• v.7 no.4
• /
• pp.274-283
• /
• 1997

It is necessary to estimate the soundness of tunnel using non-destructive tests(NDT) for effective repairs and maintenances. But, the state of tunnel lining could not be investigated using previous non-destructive techniques, due to the various types of support and accessibility only from one side in tunnel lining. Recently, the various non-destructive techniques such as ground penetrating radar(GPR) have been researched and developed for inspection of tunnel lining. In this study, the usefulness and applicability of GPR test in tunnel lining inspection has been investigated through model tests and tunnel site application. This paper described the tunnel lining inspection for lining thickness, cavity and support using GPR test. From the results of tests, we have concluded that GPR test are very useful and effective techniques to look into the interior of lining and measure the lining thickness.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.1
• /
• pp.23-35
• /
• 2009

This study was performed to investigate the bending stresses of tunnel shotcrete as a function of the coefficient of lateral earth pressure. To perform this study, a large scale model tunnel with an one-lane horseshoe shaped road tunnel was prepared. The 3 dimensional numerical analyses were carried out to verify the results obtained from the model tests. For the loading system during the tests, 11 cylinder pressure jacks which can be controlled individually were used to simulate various loading conditions. The tests were preformed three times with three different lateral earth pressure coefficients of 0.5, 1.0 and 2.0. The bending stresses of shotcrete measured in tests were compared and analyzed with those calculated from numerical analyses. As a result, it was found that the bending compressive stresses obtained from numerical analyses were similar to those of tunnel model tests and bending tensile stresses were slightly overestimated during numerical analyses.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.7 no.2
• /
• pp.133-141
• /
• 2005

The behavior of the ground in crossed zone due to the excavation of new lower tunnel rectangularly crossed to that was studied by model tests and numerical analysis in shallow cover. Results of the model tests show that earth pressure of the ground in crossed zone were redistributed due to the longitudinal arching effect by the excavation of lower tunnel. By the numerical analysis, minimum principal stress in crown of single tunnel has more decrease than parallel tunnel or crossed tunnel. Vertical stress at rectangularly crossed tunnel decrease more than single tunnel by stress shadow.

• Wind and Structures
• /
• v.12 no.5
• /
• pp.413-424
• /
• 2009

A series of wind tunnel free-decay sectional model dynamic tests were conducted to examine the effects of torsional-to-vertical natural frequency ratio of 2DOF bridge dynamic systems on the aerodynamic and dynamic properties of bridge decks. The natural frequency ratios tested were around 2.2:1 and 1.2:1 respectively, with the fundamental vertical natural frequency of the system held constant for all the tests. Three 2.9 m long twin-deck bridge sectional models, with a zero, 16% (intermediate gap) and 35% (large gap) gap-to-width ratio, respectively, were tested to determine whether the effects of frequency ratio are dependent on bridge deck cross-section shapes. The results of wind tunnel tests suggest that for the model with a zero gap-width, a model to approximate a thin flat plate, the flutter derivatives, and consequently the aerodynamic forces, are relatively independent of the torsional-to-vertical frequency ratio for a relatively large range of reduced wind velocities, while for the models with an intermediate gap-width (around 16%) and a large gap-width (around 35%), some of the flutter derivatives, and therefore the aerodynamic forces, are evidently dependent on the frequency ratio for most of the tested reduced velocities. A comparison of the modal damping ratios also suggests that the torsional damping ratio is much more sensitive to the frequency ratio, especially for the two models with nonzero gap (16% and 35% gap-width). The test results clearly show that the effects of the frequency ratio on the flutter derivatives and the aerodynamic forces were dependent on the aerodynamic cross-section shape of the bridge deck.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.11 no.3
• /
• pp.213-221
• /
• 2009

This paper presents the concrete placement method of tunnel lining to improve the concrete lining quality such as cavities, cracks of the concrete lining. In order to perform this study, the occurred cracks initially in the concrete lining are reviewed and analyzed. From the review, the improvement methods to minimize the defects of concrete lining are suggested. To confirm the efficiency of new concrete placement approaches and the scale of tunnel section, two types of the scaled model tests are carried out and analyzed in model scales of 1/20 and 1/7. The 1/20 scaled model tests are carried out using the existing experimental rigs. The 1/7 scaled model tests are carried out in new test rigs developed in this study. The concrete placement rates obtained from the experimental results are analyzed and compared with themselves. In the existing concrete placement method, 1/20 scale model test than 1/7 scale model test have increased concrete placement rates but It is clearly found that two kinds of experimental studies show the similar results in improvement methods and good agreement with new concrete placing approach.