• Geomechanics and Engineering
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• 제21권2호
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• pp.171-178
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• 2020

Mountainous areas cover more than 70% of Korea. With the rapid increase in tunnel construction, tunnel-collapse incidents and excessive deformation are occurring more frequently. In addition, longer tunnel structures are being constructed, and geologically weaker ground conditions are increasingly being encountered during the construction process. Tunnels constructed under weak ground conditions exhibit long-term deformation behavior that leads to tunnel instability. This study analyzes the behavior of the bottom region of tunnels under geological conditions of long-term deformation. Long-term deformation causes various types of damage, such as cracks and ridges in the packing part of tunnels, as well as cracks and upheavals in the pavement of tunnels. We observed rapid tunnel over-displacement due to the squeezing of a fault rupture zone after the inflow of a large amount of groundwater. Excessive increments in the support member strength resulted in damage to the support and tunnel bottom. In addition, upward infiltration pressure on the tunnel road was found to cause severe pavement damage. Furthermore, smectite (a highly expandable mineral), chlorite, illite, and hematite, were also observed. Soil samples and rock samples containing clay minerals were found to have greater expansibility than general soil samples. Considering these findings, countermeasures against the deformation of tunnel bottoms are required.

• Geomechanics and Engineering
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• 제33권5호
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• pp.439-451
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• 2023

The construction of shield tunnelling in urban sites is facing serious risks from complex and changeable underground conditions. Construction problems in the sand-clay mixed ground have been more reported in recent decades for its poor control of soil loss in tunnel face, ground settlement and supporting pressure. Since the limitations of observation methods, the conventional physical modelling experiments normally simplify the tunnelling to a plane strain situation whose results are not reliable in mixed ground cases which exhibit more complicated responses. We propose a new method for the study of the mixed ground tunnel through which mixed lays are simulated with transparent soil surrogates exhibiting different mechanical properties. An experimental framework for the transparent soil modelling of the mixed ground tunnel was established incorporated with the self-developed digital image correlation system (PhotoInfor). To understand better the response of face stability, ground deformation, settlement and supporting phenomenon to tunnelling excavation in the sand-clay mixed ground, a series of case studies were carried out comparing the results from cases subjected to different buried depths and mixed phenomenon. The results indicate that the deformation mode, settlement and supporting phenomenon vary with the mixed phenomenon and buried depth. Moreover, a stratigraphic effect exists that the ground movement around mixed face reveals a notable difference.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(II)
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• pp.170-175
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• 2003

The ASCE formula of pipeline' soil interaction force is the basis of semi-analytical relationship for buried pipelines subjected to longitudinal permanent ground deformation due to seismic induced liquefaction. However, since the ASCE formula has been developed based on the stiffness of non-liquefied region, it is needed to modify for the varied stiffness of liquefied region. With this object, the consideration of decreasing effect of soil stiffness in liquefied region is made: i.e. the spatial distributions of pipeline. soil interaction force in liquefied region. It means that the improved formula can reflect various patterns of permanent ground deformation more realistically. Through the comparative analyses using both the improved and ASCE formula, the applicability of the improved, the limitation of the existing formula and semi-analytical relationship are discussed.

• Geomechanics and Engineering
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• 제4권2호
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• pp.91-103
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• 2012

Focusing on the effect of excess pore pressure dissipation on liquefaction-induced ground deformation, a series of 1-g shaking table tests were conducted in a rigid soil container by use of saturated Toyoura sand, the relative density of which was 20-60%. These tests were subjected to the sinusoidal base shaking with step increased accelerations: 100, 200, 300 and 400 Gals for 2-4 seconds. Shaking table tests were done using either water or polymer fluid with more viscous than water, thus varying the sand permeability of model tests. Excess pore pressures, accelerations, settlements and lateral deformations were measured in each test. Test results are presented in this paper and the effect of sand permeability on liquefaction and liquefaction-induced ground deformation was discussed in detail.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1343-1350
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• 2005

In this study, the whole deformation conditions of domestic old tunnels and reinforcement methods for deformation tunnels were investigated and analysed, and the present conditions, occurrence cause and reinforcement methods of cavity behind the tunnel lining were investigated and analysed comprehensively. The deformation causes of domestic old tunnels could be classified in three kinds : change of earth pressure operating tunnel ground, material problem of concrete lining, mistake of design and construction. As a result of analysis, the tunnel deformation was occurred by not specific cause but various cause As a result of investigation for 455 domestic tunnel data, more than 70% of the tunnel deformation was related to leakage and the other deformation cause also accompanied leakage mostly. An applied reinforcement method was related to leakage and flood prevention measures, but application of reinforcement method for boundary area between tunnel and ground and tunnel periphery which influence on the tunnel stability was still defective. The cavity of domestic old tunnel occupied about 16% of the total tunnel length and about 68% of cavity was located in the crown of tunnel, and besides, the occurrence cause of cavity was analysed to design, construction and management cause. The filling method for cavity using filling material was comprehensively appling to cavity behind tunnel lining.

• 한국지반공학회지:지반
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• 제14권1호
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• pp.81-92
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• 1998

화력발전소에서 대량으로 부산 되어 폐기 처리되고 있는 석탄회 폐기물로 조성된 지반을 안정 처리하여 사용하거나 또는 이러한 석탄회를 건설공사의 직접적인 재료로 활용하게 되면 결국 폐자원을 산업자원화 함으로서 건설자재 난을 해소할 수 있게 된다. 본 연구에서는 석탄회를 성토재 및 매립재로서 대량 활용할 경우와 지반변형해석에 필요한 적용 모델과 그 적용성을 중심으로 검토하였다. 그 중 Cam-clay model은 흙의 다양한 응력경로에 대해 배수와 비배수 조건에서 재하하는 동 안 변위와 공극수압을 나타낼 수 있는 완전한 구성식을 제공하고, 필요로 하는 토질정수가 극소수이고 모든 것을 실내실험을 통해 측정할 수 있는 장점이 있다. 토질기본시험, 등방압밀 및 비배수 삼축압축시험 등을 통하여 Camflay mode숙 제반 parameter를 구하였고, 수치해석을 수행하여 시험 결과와 비교하였다. 시험 결과와 수치 해석결과에서 각각 구한 parameter의 오차는 매우 근소 한 것으로 나타났다. 시험을 통해 결정한 비회와 저회 5 : 5 적정혼합회의 Parameter들은 인공으로 조성된 석탄회 매립지반의 변형해석에서 Cam-clay model을 이용하는 데에 기초자료로서 활용이 가능할 것으로 판단된다.

• 한국터널지하공간학회 논문집
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• 제19권6호
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• pp.887-903
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• 2017

터널이 시공되는 환경은 다양하여 지형이 평탄하지 않거나 지표가 경사가 진 경우가 많으며, 이런 경우에는 지반내 응력의 분포가 일정하지 않다. 그러므로 이와 같은 환경에서는 얕은 터널 굴착에 따라 종방향 하중전이 특성이 달라서 그 영향이 불명확하다. 또한, 시공방법이나 지반조건 및 굴진면의 변위형태 등이 종방향 하중전이 발생경향에 영향 줄 것이므로, 이를 종합적으로 고려한 연구가 필요하다. 따라서 본 연구에서는 지반의 경사를 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 모사하고, 굴진면의 변위형태(상부 큰 변위, 등변위, 하부 큰 변위)에 따른 굴진면의 토압과 터널 천단상부의 종방향 하중전이 특성을 실험적으로 규명하였다. 연구결과 굴진면에서 변위가 발생하면 굴진면 토압이 감소하고 터널의 천단 하중이 증가하며, 굴진면의 토압변화량에 따라 터널 천단상부의 하중전이의 크기와 발생경향이 변화되었다. 따라서 굴진면의 토압변화가 터널 종방향 하중전이에 직접적인 영향을 주는 것을 알 수 있었다. 지표경사가 작으면 하중전이 영역이 넓어지며 지표경사가 커질수록 종방향으로 전이되는 경향이 감소하고 굴진면 부근에서 집중되었다. 또한, 굴진면의 변위형태에 따라 종방향으로 전이되는 하중의 분포경향도 달라지므로 종방향 지반의 응력조건과 굴진면의 변위형태는 터널 종방향 하중전이의 형태와 크기에 영향을 주는 것으로 분석되었다.

• 한국지반공학회논문집
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• 제15권5호
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• pp.57-64
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• 1999

근거리 발파에 의한 구조물 피해의 임계진동수준을 결정하기 위해 구조물의 기존 균열 변형과 지반 진동수준을 계측하였다. 구조물에 대한 발파진동의 피해를 평가하기 위해 일상적인 환경변화에 의한 기존 균열의 최대 변형량을 고려한 새로운 기준을 제시하였다. 본 실험에서 사용된 2 채의 농어촌 조적조 가옥에 대한 시험 결과를 보면, 구조물에 피해를 유발하기 위한 진동 수준은 설계 기준보다 훨씬 더 큰 수준임을 알 수 있다.

• 한국지반환경공학회 논문집
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• 제8권6호
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• pp.29-36
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• 2007

지표면 침하량, 침하 기울기 그리고 터널주변의 지반변위에 대한 관리와 예측은 도심지 터널 시공에 있어서 주요한 인자가 된다. 본 논문은 도심지 NATM터널의 변형거동에 대한 세밀한 분석을 위하여 사례분석과 수치해석적인 방법을 통하여 굴착에 따른 지반 평가와 거동 예측을 수행하였다. 수치해석적인 방법은 FLAC-2D 변형률 연화모델과 탄소성모델을 이용하였다. 현장계측은 지표면 침하와 지중변위를 수행하였으며, 계측결과는 시공중 설계물성치의 재설정에 이용되어졌다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.229-234
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• 2006

There are still some key problems having to be solved in theory and technique applications when GPS is used to monitor the vertical deformation of ground with high precision. Utilizing the GPS technology to monitor the deformation of the land subsidence and ground fissure in Xi'an, this paper puts forward advice that the datum frame of GPS network has significant influence on the precision and accuracy of the vertical deformation results by some research. The co-authors make some theoretical study of the datum error and practice by establishing the datum error models, especially the influence of scale and azimuth datum errors on GPS monitoring network. Then the datum frame design methods and arithmetic of GPS monitoring network are presented and have taken a good effect.