• Structural Engineering and Mechanics
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• 제78권5호
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• pp.637-649
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• 2021

Great efforts have been conducted to investigate the seismic performances of the arch and rectangular underground structures, however, the differences between seismic responses of these two types of underground structures, especially the vault radian influencing the seismic responses of arch structures are not clarified. This paper presents a detailed numerical investigation on the seismic responses of arch underground structures with different vault radians, and aims to illustrate the rule that vault radian affects the seismic responses of underground structures. Five arch underground structures are built for nonlinear soil-structure interaction analysis. The internal forces of the structural components of the underground structures only under gravity are discussed detailedly, and an optimum vault radian for perfect load-carrying functionality of arch underground structures is suggested. Then the structures are analyzed under seven scaled ground motions, amounting to a total of 35 dynamic calculations. The numerical results show that the vault radian can have beneficial effects on the seismic response of the arch structure, compared to the rectangular underground structures, causing the central columns to suffer smaller axial force and horizontal deformation. The conclusions provide some directive suggestions for the seismic design of the arch underground structures.

• Geomechanics and Engineering
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• 제34권3호
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• pp.303-316
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• 2023

With the development and utilization of urban underground space, the artificial ground freezing technology has been widely used in the construction of underground engineering in soft soil areas. The mechanical properties of soft clay changed greatly after freezing and thawing, which affected the seismic performance of underground structures. In this paper, a series of triaxial tests were carried out to study the dynamic response of the freezing-thawing clay under the seismic load considering different dynamic stress amplitudes and different confining pressures. The reduction factor of dynamic shear stress was determined to correct the amplitude of the seismic load. The deformation development mode, the stress-strain relationship and the energy dissipation behavior of the soft clay under the seismic load were analyzed. An empirical model for predicting accumulative plastic strain was proposed and validated considering the loading times, the confining pressures and the dynamic stress amplitudes. The relevant research results can provide a theoretical reference to the seismic design of underground structures in soft clay areas.

• 한국전산유체공학회지
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• 제17권1호
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• pp.36-43
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• 2012

When a high-speed train passes an underground station, large pressure waves are generated due to the piston effect. These pressure waves can cause the problems of vibration and noise as well as the ear discomfort of passengers at the underground station. This work numerically analyzed the pressure wave generation and propagation in an high-speed railway underground station, and the optimal location for vent shafts was studied to improve the passenger comfort by reducing the magnitude of the pressure wave and its rate of change. The evolution of pressure field in the underground station was calculated using a CFD(Computational Fluid Dynamics) software(Fluent), where the axis-symmetric two-dimensional model verified by Wu was used. And this study is applied to modelling of the underground station and the tunnel from Daegok station A-line of GTX(Great Train Express). From the result, we can have a conclusion that the role of vent shafts respectively were different according to the position in and out the underground station. Also Vent shaft in the underground station widely reduced pressure magnitude. And vent shaft out underground station reduced initial pressure peak value. Double vent shafts installed at tunnel toward station entrance and inside of the tunnel are the most efficient to reduce pressure. and pressure reduction increases according to the number of vent shaft.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1991년도 봄 학술발표회 논문집
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• pp.20-25
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• 1991

In order to predict properly the effects of ground motion associated wi th earthquakes on underground radioactive waste disposal facilities, understanding of the structural behavior of an underground opening in discontinuous rook masses subjected to dynamic loadings is essential. Therefore, this paper includes literature review on computational models for discontinuous rook masses and on mathematical models for the structural analysis of underground openings. Then, structural analyses of underground openings using the distinct element computer program written for the static and dynamic analysis of discontinuous rook masses have been performed.

• 설비공학논문집
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• 제25권8호
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• pp.427-431
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• 2013

Ground heat pump systems utilize the annually stable underground temperature to supply heat for space heating and cooling. The underground temperature affects not only the underground ecosystem, but also the performance of these systems. However, in spite of the widespread use of these systems, there have been few researches on the effect of the systems on underground temperature. In this research, case studies with numerical simulation have been conducted, in order to estimate the effect of ground heat pump systems on underground temperature. The simulation was coupled with the ground water-ground heat transfer model and the ground surface heat transfer model. In the result, it was found that the underground change depends on the heat transfer from the ground surface, the heat exchange rate, and the heat conductivity of soil.

• 터널과지하공간
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• 제28권4호
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• pp.304-324
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• 2018

싱가포르는 국토가 부족한 도시 국가의 특성으로 인해 지하 공간의 개발 및 활용을 정부차원에서 전 국가적으로 강력하게 추진하고 있다. 특히 지하철과 지하 도로와 같은 일반 얕은 심도의 지하공간의 활용뿐 아니라 대규모 지하공간 사업으로서 암반 내 지하 탄약 저장고 프로젝트를 성공적으로 마친 이후, 두번째 대규모 암반 지하공간 프로젝트인 Jurong Rock Cavern을 얼마전 준공한 바 있다. 본 논문에서는 싱가포르의 지질 분석을 통해 암반 지하공간 개발의 조건에 대해 평가한 후, 싱가포르의 다양한 지하공간 개발의 역사와 현황을 살펴본다. 지하 저수지, 지하 자동화 물류 시스템 및 물류 저장 창고 등 정부 차원에서 향후 추진이 예상되는 창의적인 암반내 주요 지하공간 관련 계획 및 기술적인 이슈들에 대해서 소개한다. 또한 이러한 대규모 암반 지하공간 개발에 관련된 향후 문제와 이슈들에 대해서 논의한다. 싱가포르의 이러한 적극적인 지하공간 개발 움직임은 또한 암반공학 및 업계에 향후 많은 기회와 과제를 줄 것으로 기대된다.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.69-75
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• 2000

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.

• Geomechanics and Engineering
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• 제32권4호
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• pp.411-426
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• 2023

Soft clay is widely distributed in the southeast coastal areas of China. Many large underground structures, such as subway stations and underground pipe corridors, are shallow buried in the soft clay foundation, so the dynamic characteristics of the soft clay must be considered to the seismic design of underground structures. In this paper, the dynamic characteristics of saturated soft clay in Shanghai under the bidirectional excitation for earthquake loading are studied by dynamic triaxial tests, comparing the backbone curve and hysteretic curve of the saturated soft clay under different confining pressures with those under different vibration frequencies. Considering the coupling effects of the confining pressure and the vibration frequency, a fitting model of the maximum dynamic shear modulus was proposed by the multiple linear regression method. The M-D model was used to fit the variations of the dynamic shear modulus ratio with the shear strain. Based on the Chen model and the Park model, the effects of the consolidation confining pressure and the vibration frequency on the damping ratio were studied. The results can provide a reference to the earthquake prevention and disaster reduction in soft clay area.

• Membrane and Water Treatment
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• 제11권3호
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• pp.173-177
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• 2020

Wastewater treatment plants (WWTPs) have been recognized as one of the significant greenhouse gas (GHG) generators, due to the complex biochemical reaction and huge consumption of energy and materials. Recently, WWTPs have been built underground and they will be confronted with the challenges of mitigating GHG emissions and improving the quality of treated wastewater. Here, we focus on estimating GHG emissions to set up effective management plans for a WWTP built underground. First, we apply the process-based life cycle assessment (LCA) with an inventory database of the underground WWTP for a case study. Then, we identify significant factors affecting GHG emissions during service life using sensitivity analysis and suggest the proper tactics that could properly reduce GHG emissions from the WWTP.

• 대한건축학회논문집:구조계
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• 제35권6호
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• pp.129-137
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• 2019

The purpose of this study is to present systematic information and direction to urban underground space development industry, civil engineering and R&D. Regarding the development of urban underground space, the situation in Korea, especially now in Seoul, can be called an underground Renaissance. The Superground project, which has been going on for several years through international competition, is now completed and is about to open the Seoul Architecture Museum. Leading underground space complex development project of Yeongdongdaero, which is the largest living underground space in human history, spectral projects such as the Seoul section of the GTX routes, making underground roads of the Dongbu Expressway and the Seobu Expressway are now speeding up progress. Recently, plans have been made to use the underground more actively through the restructuring project of Gwanghwamun Square, the face of Seoul. And then, patents are indispensable resources for establishing a strategy for R&D as one of the indices showing what technologies have been developed and what technology development will be done in the future. Based on this background, this study attempts to classify and define the technical elements of urban underground space development through the analysis of patents of major countries in the world, and analyze and present state of technology level and situation accordingly.