• Earthquakes and Structures
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• v.24 no.1
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• pp.53-64
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• 2023

Earth fissures with several kilometers will inevitably approach or cross the metro line, significantly threatening the safety of the underground structure in the earth fissure site. However, the influence of the earth fissure site's amplification effect on the metro station's dynamic response is still unclear. A representative earth fissure in Xi'an was taken as an example to establish a numerical model of a metro station in the earth fissure site. The dynamic response characteristics of the metro stations at different distances from the earth fissure under various seismic waves were calculated. The results show that the existence of the earth fissure significantly amplifies the dynamic response of the nearby underground structures. The responses of the axial force, shear force, bending moment, normal stress, horizontal displacement, inter-story drift, and relative slip of the metro station were all amplified within a specific influence range. The amplification effect increases with the seismic wave intensity. The amplification effect caused by the earth fissure has relatively weak impacts on the axial shear, shear force, bending movement, normal stress, and horizontal movement; slightly larger impacts on the inter-story drift and acceleration; and a significant impact on the relative slip. The influence ranges of the axial force and normal stress are approximately 20 m. The influence ranges of the acceleration and inter-story drift can reach 30 m. Therefore, the seismic fortification level of the underground structure in the earth fissure site needs to be improved.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.685-690
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• 2023

It was analyzed that the volume of deep excavation works adjacent to existing underground structures is increasing according to the population growth and density of cities. Currently, many underground structures and tracks are damaged by external factors, and the cause is analyzed based on the measurement results in the tunnel, and measurements are being made for post-processing, not for prevention. The purpose of this study is to analyze the effect on the deformation of the structure due to the excavation work adjacent to the urban railway track in use. In addition, the safety of structures is evaluated through machine learning techniques for displacement of structures before damage and destruction of underground structures and tracks due to external factors. As a result of the analysis, it was analyzed that the model suitable for predicting the structure management standard value time in the analyzed dataset was a polynomial regression machine. Since it may be limited to the data applied in this study, future research is needed to increase the diversity of structural conditions and the amount of data.

• Explosives and Blasting
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• v.34 no.3
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• pp.10-16
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• 2016

Recently, transition from open pit to underground mining in limestone mines is an increasing trend in Korea due to environmental issues such as noise, dust and vibrations caused by crushers and equipment. The severe damages in the surrounding rock mass of underground opening caused by explosive blasting may lead to rock fall hazards or casualties. It is well known that variables which mainly affect blast-induced rock falls in underground mining are: blast vibration level, joint orientation and distribution and shape of the cross sections of underground structures. In this study, UDEC program, which is a DEM code, is used to simulate blast vibration-induced rock fall in underground openings. Variation of joint space, joint angle and joint normal stiffness was considered to investigate the effect of joint characteristics on the blast vibration-induced rock fall in underground opening. Finally, jointed rock mass models considering blast-induced damage zone were examined to simulate the critical blast vibration value which may cause rock falls in underground opening.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1539-1543
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• 2011

Due to recent large earthquakes around the world, there are increasing social needs for seismic safety of urban railway infrastructures. Urban railway infrastructures are applied different seismic performance evaluation procedure each of overground structures, underground structures and bridge structures, and the characteristics of urban railway infrastructures are not properly considered in the procedure. This study presents problems in the existing seismic performance evaluation procedure of urban railway infrastructures and proposes necessities of unified evaluation procedure.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.655-660
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• 2002

Major deterioration in concrete structures are salt attack and carbonation. Especially severe problems due to carbonation occur in tile concrete structures of city, tunnel, underground structures. Cracks in concrete during service life including early age due to hydration heat and/or shrinkage accelerate the diffusion of concrete so that the deterioration is also accelerated. In this study, carbonation depths of both non-cracked concrete and cracked concrete are evaluated and weight change test and TGA are carried out. Through the tests, a relation between water-cement ratio and carbonation depth is derived and also carbonation increase rate is derived in the function of crack width.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.468-474
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• 2005

Recently 'Earthquake Resistance Design Regulations for Subway structures' has been established. It is the first time in our country. In this paper the regulations is reviewed and expalined briefly. Contents for the Performance Based Design Critetia and the estimation method for the design earthquake reponse spectrum in underground structures are reviewed. Earthquake resistance design for the evaluation of liquifaction, boundary spring coefficients for structural analysis modelling and soil response displacements are investigated and described also. Earthquake resitance design details shall be explained.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.93-100
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• 2000

In this study, we used photoelastic coating method which is a kind of model test for examining the stress condition of rock masses around underground structures. Using this method, we could know adaptability and usefulness of photoelastic coating method for various shape of tunnel models. And, in spite of higher cross section efficiency, square shape model showed unstable status because of high stress concentration. So, we cut the slits at the each corner of tunnel, and we could make more stable stress condition by means of moving high stress concentration to rock mass.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.55-64
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• 2002

This paper presents a brief review of flexible retaining structure and the most significant methods developed to predict their behavior on underground excavations. Some observations are made about the future directions that the design of retaining systems may take , as there are still some problems where uncertainity exists, in soil-structure interaction and evaluation of strength parameters etc. And also reviewed papers presented in 2002 Fall National Conference of KGS.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.139-148
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• 1994

Rapid industrialization and urbanization caused by the high economic growth of the country requires optimization of land usage as well as the expansion of underground space. Therefore the construction of large and deep basements is inevitable in built up areas where the braced excavation for earth retaining structures may create many problems such as settlement and damages of nearby buildings and underground utilities. In this work, some of major influential factors concerning the stability of braced excavation are investigated and the results are compared with the field observation results. The ground water table, applied strut forces, horezontal wall displacement, infilling materials in the rock joints were found to be the most critical factors influencing the stability of braced walls constructed in the layered ground. Magnituide and type of the wall deformation was closely related to the pattern of the surface settlement. The stability of braced walls are described in terms of strut forces.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.553-561
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• 2010

Like the shotcrete can be deteriorated by chemical compounds as service years increase, the grout which is used to fasten the cablebolt(rockbolt) system in the underground structures also can be deteriorated by chemical compounds such as sulphate and/or chloride contained in groundwater during service years. This can induce issues on the long term durability of cablebolt(rockbolt) system and consequently on the stability of underground structures. In this study, the deteriorations of long term durability of cement mortar grout by each chemical compound of sulphate or chloride are studied experimentally and also complex deterioration by the mix of sulphate and chloride is investigated. Based on the results obtained in this study, the characteristics and prediction of deterioration of long term durability of cement mortar grout for cablebolt(rockbolt) system are suggested.