• Computers and Concrete
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• v.21 no.4
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• pp.399-406
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• 2018

The present study focuses on the performance of basalt fiber reinforced concrete (BFRC) lining in tunnel situated in sandstone rock when subjected to internal blast loading. The blast analysis of the lined tunnel is carried out using the three-dimensional (3-D) nonlinear finite element (FE) method. The stress-strain response of the sandstone rock is simulated using a crushable plasticity model which can simulate the brittle behavior of rock and that of BFRC lining is analyzed using a damaged plasticity model for concrete capturing damage response. The strain rate dependent material properties of BFRC are collected from the literature and that of rock are taken from the authors' previous work using split Hopkinson pressure bar (SHPB). The constitutive model performance is validated through the FE simulation of SHPB test and the comparison of simulation results with the experimental data. Further, blast loading in the tunnel is simulated for 10 kg and 50 kg Trinitrotoluene (TNT) charge weights using the equivalent pressure-time curves obtained through hydrocode simulations. The analysis results are studied for the stress and displacement response of rock and tunnel lining. Blast performance of BFRC lining is compared with that of plain concrete (PC) and steel fiber reinforced concrete (SFRC) lining materials. It is observed that the BFRC lining exhibits almost 65% lesser displacement as compared to PC and 30% lesser displacement as compared to SFRC tunnel linings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.95-104
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• 2006

The presence of cavitations under pavements or behind tunnel linings of concrete is likely to result in collapse. One method of detecting such voids by non-destructive means is low frequency type radar(GPR). By the way, the size and thickness of small cavitation can't be detected by the present radar technology with low frequency and low resolution when it apply to civil structures like that. To overcome these problems and limitations, this study aims to develope and propose a new analysis method for estimating the depth, cross-sectional size and thickness of cavitations using low frequency radar. A new proposed method is based on the experiments that are carried out for analyzing the correlation between the measurement values(the amplitudes of radar return) of low frequency radar and various type of cavitations. In this process, the threshold value for radar image processing which aims to represent only cavitations to be fitted size can be obtained. As the results, it is clarified that a proposed method has a possibility of estimating cavitation depth, size and thickness with good accuracy in laboratory scale.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.77-84
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• 2007

One of the most sensitive design specifications to be considered is infiltration and external pore-water pressures on underground structure construction. Development of pore-water pressure may accelerate leakage and consequently cause deterioration of the lining. In this paper, the development of pore-water pressure due to malfunctioning of drainage system and its potential effect on the linings are investigated using physical model tests. The deterioration procedure was simulated by controlling both permeability and flow rate. Development of pore-water pressure was monitored on the lining using pore pressure measurement cells. Test results identified the mechanism of pore-water pressure development on the tunnel lining. In addition, they showed that controlling flow rate is more effective method fur simulating deterioration procedure than permeability control. The laboratory model tests were reproduced using coupled numerical method, and showed that the effect of deterioration of drainage system can be theoretically expected using coupled numerical modeling method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.413-420
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• 1998

In this study, an expert system is developed to evaluate a safety of tunnel structures. Using a dynamic finite element analysis module, this expert system predicts dynamic responses of a concrete lining surface which a transient force is applied on and estimates the condition between the concrete lining and surrounding ground. The evaluation parameter values of the module are multi-reflected wave frequency and amplitude of the dynamic responses. The multi-reflected wave frequency represents the depth of concrete lining, and the other parameter, the amplitude of the frequency, is utilized for detecting the internal flaws. A comparison of the dynamic responses between numerical and experimental model test verifies an effectiveness of this system. By this expert system, the safety of tunnel structures and the detection of internal flaws of concrete linings are estimated quantitatively.

• Geomechanics and Engineering
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• v.29 no.3
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• pp.349-357
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• 2022

Abnormal climate events are occurring frequently around the world. In particular, cold waves and heavy snow lead to damage and deterioration of facilities, which can cause loss of life or property damage, such as shortening the lifespan of facilities. Therefore, it is very important to prepare an appropriate maintenance system and to establish a strategy to cope with abnormal weather conditions. In this study, laboratory freezing experiments were performed to analyze the freeze-thaw characteristics affecting the tunnel concrete lining, and heat flow analysis was carried out based on the test results. Based on these experimental and theoretical analysis results, quantitative freeze-thaw evaluation criteria for tunnel concrete linings were proposed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.9
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• pp.3797-3822
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• 2020

The inspection of cracks on the surface of tunnel linings is a common method of evaluate the condition of the tunnel. In particular, determining the thickness and shape of a crack is important because it indicates the external forces applied to the tunnel and the current condition of the concrete structure. Recently, several automatic crack detection methods have been proposed to identify cracks using captured tunnel lining images. These methods apply an image-segmentation mechanism with well-annotated datasets. However, generating the ground truths requires many resources, and the small proportion of cracks in the images cause a class-imbalance problem. A weakly annotated dataset is generated to reduce resource consumption and avoid the class-imbalance problem. However, the use of the dataset results in a large number of false positives and requires post-processing for accurate crack detection. To overcome these issues, we propose a crack detection method using a ternary classifier. The proposed method significantly reduces the false positive rate, and the performance (as measured by the F1 score) is improved by 0.33 compared to previous methods. These results demonstrate the effectiveness of the proposed method.

• Smart Structures and Systems
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• v.21 no.5
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• pp.583-590
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• 2018

Nowadays, many tunnels have been commissioned for several decades, which require effective inspection methods to assess their health conditions. The ambient vibration test has been widely adopted for the damage identification of concrete structures. In this study, the vibration characters of tunnel lining shells built with forepoling method was analyzed based on the analytical solutions of the Donnell-Mushtari shell theory. The broken rock, foreploing, rock-concrete contacts between rock mass and concrete lining, was represented by elastic boundaries with normal and shear stiffness. The stiffness of weak contacts has significant effects on the natural frequency of tunnel lining. Numerical simulations were also carried out to compare with the results of the analytical methods, showing that even though the low nature frequency is difficult to distinguish, the presented approach is convenient, effective and accurate to estimate the natural frequency of tunnel linings. Influences of the void, the lining thickness and the concrete type on natural frequencies were evaluated.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.307-320
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• 1998

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 many problems in supporting and managing tunnels. Therefore the analysis of the cracks is quite strongly required. In this study, mechanical behaviour of a tunnel lining was examined by model tests and by numerical analyses. Especially the model test was examined for double linings including shotcrete and concrete lining. The model tests were carried out under various conditions taking different loading shapes, horizontal stresses, thicknesses of linings and double lining, vault opening behind the concrete lining and rock-like medium surrounding the lining. Due to horizontal stress, compressive stress prevailed on the lining. Thus the bearing capacity of the lining increased. The existence of a vault opening behind the concrete lining reduced the bearing capacity by the similar amount of reduction of concrete lining thickness. Rock-like medium cast around the side wall of the lining restrained the deflection of the lining, and the bearing capacity for cracking and failure increased vary much. In numerical analyses a algorithm which can analysis the double lining by introduction of interface element was developed. And the results of the numerical analyses were compared with the results of the model tests.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.229-232
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• 2005

More than effectively judging the existence of voids behind concrete tunnel linings or under concrete pavements, this research aims to develop the analysis algorithm of radar capable of estimation of the shape of specific voids. To detect or estimate void shapes in non-reinforced concrete, the simulation analysis model of transmission and reflection wave of electromagnetic radar is used. This radar simulation model is carried out with various void shapes. As the results, a proposed method in this study has a possibility of detecting or estimating void shapes with good accuracy.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.423-446
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• 2023

Shield TBM tunnel linings are segmented into segments and rings. This study investigates the response characteristics of the stress and displacement of the segment lining under seismic waves through modeling that considers the interface behavior between segments by applying a shell interface element to the contact surface between segments and rings. And there is no management criteria for ovaling deformation of segment linings in Korea. So, this study the ovality criteria and meaning of segment lining. The results of study showed that the distribution patterns of stress and displacement under seismic waves were similar between continuous linings and segment linings. However, the maximum values of stress and displacement showed differences from segment linings. The stress distribution of the continuous lining modeled as a shell type has a stress distribution that has continuity in the 3D cylindrical shape, but the segment lining is concentrated outside the segment, and the largest stress occurs at the location where the contact surface between the segment and the ring is concentrated. This intermittent and localized stress distribution shows an increasing as the ovality of the lining increases at seismic waves. The ovality at which the increase in stress distribution begins to show irregularity and localization is about 150‰. Ovality of 150‰ is an unrealistic value that cannot represent actual lining deformation. Therefore, the ovality of the segment lining increase with depth, but it does not have a significant impact on the stability caused by seismic load.