• Geomechanics and Engineering
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• 제24권4호
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• pp.323-335
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• 2021

This paper aims to estimate the range of the excavation damaged zone (EDZ) formation caused by the tunnel boring machine (TBM) advancement through dynamic three-dimensional large deformation finite element analysis. Large deformation analysis based on Coupled Eulerian-Lagrangian (CEL) analysis is used to accurately simulate the behavior during TBM excavation. The analysis model is verified based on numerous test results reported in the literature. The range of the formed EDZ will be suggested as a boundary under various conditions - different tunnel diameter, tunnel depth, and rock type. Moreover, evaluation of the integrity of the tunnel structure during excavation has been carried out. Based on the numerical results, the apparent boundary of the EDZ is shown to within the range of 0.7D (D: tunnel diameter) around the excavation surface. Through series of numerical computation, it is clear that for the rock of with higher rock mass rating (RMR) grade (close to 1st grade), the EDZ around the tunnel tends to increase. The size of the EDZ is found to be direct proportional to the tunnel diameter, whereas the depth of the tunnel is inversely proportional to the magnitude of the EDZ. However, the relationship between the formation of the EDZ and the stability of the tunnel was not found to be consistent. In case where the TBM excavation is carried out in hard rock or rock under high confinement (excavation under greater depth), large range of the EDZ may be formed, but less strain occurs along the excavation surface during excavation and is found to be more stable.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2002년도 창립 20주년기념 국제학술대회
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• pp.229-238
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• 2002

The calculation of earthwork plays a major role in plan or design of many civil engineering projects, and thus it has become very important to improve the accuracy of earthwork calculation. In this paper, we propose an algorithm of finding a cubic spline surface with the free boundary conditions, which interpolates the given three dimensional data, by using B-spline and an accurate method to estimate pit-excavation volume. The proposed method should be of interest to surveyors especially concerned with accuracy of volume computations. We present some computational results showing that our proposed method provides good accuracy.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제5권1호
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• pp.40-45
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• 2002

The calculation of earthwork plays a major role in the planning and design phases of many civil engineering projects, such as seashore reclamation; thus, improving the accuracy of earthwork calculation has become very important. In this paper, we propose an algorithm for finding a cubic spline surface with the free boundary conditions, which interpolates the given three-dimensional data, by using B-spline and an accurate method to estimate pit-excavation volume. The proposed method should be of interest to surveyors, especially those concerned with accuracy of volume computations. The mathematical models of the conventional methods have a common drawback: the modeling curves form peak points at the joints. To avoid this drawback, the cubic spline polynomial is chosen as the mathematical model of the new method. In this paper, we propose an algorithm of finding a spline surface, which interpolates the given data, and an appropriate method to calculate the earthwork. We present some computational results that show the proposed method, of the Maple program, provides better accuracy than the method presented by Chen and Lin.

• Korean Journal of Geomatics
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• 제2권1호
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• pp.25-29
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• 2002

The calculation of earthwork plays a major role in plan or design of many civil engineering projects, and thus it has become very important to improve the accuracy of earthwork calculation. In this paper, we propose an algorithm for finding a cubic spline surface with the free boundary conditions, which interpolates the given three dimensional data, by using B-spline and an accurate method to estimate pit-excavation volume. The proposed method should be of interest to surveyors especially concerned with accuracy of volume computations. We present some computational results showing that our proposed method provides good accuracy.

• Geomechanics and Engineering
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• 제16권3호
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• pp.295-308
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• 2018

The excavation of twin tunnels is a process that destabilizes the ground. The stability of the tunnel lining, the control of ground displacements around the tunnel resulting from each excavation and the interaction between them must be controlled. This paper provides a new approach for replacing the costly 3D analyses with the equivalent 2D analyses that closely reflects the in-situ measurements when excavating twin tunnels. The modeling was performed in two dimensions using the FLAC2D finite difference code. The three-dimensional effect of excavation is taken into account through the deconfinement rate ${\lambda}$ of the soil surrounding the excavation by applying the convergence-confinement method. A comparison between settlements derived by the proposed 2D analysis and the settlements measured in a real project in Algeria shows an acceptable agreement. Also, this paper reports the investigation into the changes in deformations on tunnel linings and surface settlements which may be expected if the twin tunnels of T4 El-Harouche Skikda were constructed with a tunneling machine. Special attention was paid to the influence of the excavation phase shift distance between the two mechanized tunnel faces. It is revealed that the ground movements and the lining deformations during tunnel excavation depend on the distance between the tunnels' axis and the excavation phase shift.

• 한국터널지하공간학회 논문집
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• 제6권1호
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• pp.71-83
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• 2004

본 연구의 목적은 막장전방에 연약대가 존재할 때 터널 3차원 내공변위를 여러 가지 방법으로 해석하여 변위의 발생경향을 밝히고 지질변화를 예측하는 해석기법을 제시하는 것이다. 안정된 지하 암반에 터널을 굴착하게 되면, 터널 막장면을 포함한 무지보 굴착면 주위에 3차원적인 하중전이 현상이 나타나는데 막장 전방의 지반 상태가 변화하거나 연약대가존재하면 특정한 변위 경향을 보이는 것이 3차원 계측 및 수치해석결과 확인되었다. 그러므로, 시공중인 터널 내에서 3차원 절대 내공 변위를 측정하여 본 연구에서 제시된 계측해석 기법 (L/C비, $C/C_o$ 등)을 적용하면 터널 막장 전방의 지층변화나 연약대의 존재를 사전에 예측할 수 있을 것으로 판단된다.

• Geomechanics and Engineering
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• 제28권3호
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• pp.265-281
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• 2022

A set of slurry shield test system capable of cutter cutting and slurry automatic circulation is used to investigate the deformation characteristics, the evolution characteristics of support resistance and the distribution and evolution process of earth pressure during excavating and collapsing of slurry shield tunneling in circular-gravel layer. The influence of cover-span ratio on surface subsidence, support resistance and failure mode of excavation face is also discussed. Three-dimensional numerical calculations are performed to verify the reliability of the test results. The results show that, with the decrease of the supporting force of the excavation face, the surface subsidence goes through four stages: insensitivity, slow growth, rapid growth and stability. The influence of shield excavation on the axial earth pressure of the front soil is greater than that of the vertical earth pressure. When the support resistance of the excavation face decreases to the critical value, the soil in front of the excavation face collapses. The shape of the collapse is similar to that of a bucket. The ultimate support resistance increase with the increase of the cover-span ratio, however, the angle between the bottom of the collapsed body and the direction of the tunnel excavation axis when the excavation face is damaged increase first and then becomes stable. The surface settlement value and the range of settlement trough decrease with the increase of cover-span ratio. The numerical results are basically consistent with the model test results.

• 한국지반환경공학회 논문집
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• 제24권12호
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• pp.39-45
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• 2023

본 논문에서는 3차원 수치해석을 통해 철도 노반에 인접한 굴착공사 시 궤도의 틀림을 분석하였다. 철도 노반에 인접한 굴착 공사는 열차 주행에 영향을 미칠 가능성이 높아 공사 시 인접 구조물의 안정성 및 영향성 검토를 필수로 수행하고 있지만, 그럼에도 불구하고 공사에 따른 침하 및 궤도틀림이 지속적으로 보고되고 있다. 굴착공사로 인한 지하수위, 지반의 응력 상태 변화 등은 인접 굴착 공사에 따른 구조물의 침하와 궤도틀림의 원인으로 지적되고 있다. 따라서, 본 연구에서는 인접 굴착 공사 시 궤도 틀림을 유발하는 인자를 변수로 고려하여 수치해석을 수행하였으며 운행 열차를 모사하기 위해 KRL-2012 표준 열차하중을 적용하였다. 분석 결과, 열차하중의 위치, 굴착지점과의 거리가 궤도틀림에 큰 영향을 미치는 것으로 나타났으며, 열차 하중이 작용할 때 궤도 틀림이 크게 발생하는 것으로 나타났다. 지하수위의 영향은 크지 않은 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.988-997
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• 2006

In this paper, a reliability-groundwater flow program is developed by coupling the 3-D finite element numerical groundwater flow program with first and second order reliability program. The numerical groundwater program developed called DGU-FLOW is verified by solving the examples of groundwater flow through the underground excavation and comparing the results with those of commercial MODFLOW 3D programs. Reliability routine of the program is also verified by comparing the probability of failure of the flow model from FORM/SORM with that of Monte-Carlo Simulation. The difference of out-flux and total head calculated near the bottom of the excavation using the deterministic 3D groundwater flow and the commercial programs was negligible. The reliability analysis of the groundwater flow showed that the probability of failure from the first and second order reliability method are quite close that of Monte-Carlo Simulation. Therefore, the developed program is considered effective for analyzing the groundwater flow with uncertainty in hydraulic conductivity of the soils.

• Geomechanics and Engineering
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• 제21권2호
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• pp.215-226
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• 2020

The magnitude and distribution of tunnel deformation were widely discussed topics in tunnel engineering. In this paper, a three-dimensional (3D) finite element program was used for the analysis of various horseshoe-shaped opening expressway tunnels under different geologies. Two rock material models - Mohr-Coulomb and Hoek-Brown were executed in the process of analyses; and the results show that the magnitude and distribution of tunnel deformation were close by these two models. The tunnel deformation behaviors were relevant to many factors such as cross-sections and geological conditions; but the geology was the major factor to the normalized longitudinal deformation profile (LDP). If the time-dependent factors were neglected, the maximum displacements were located at the distance of 3 to 4 tunnel diameters behind the excavation face. The ratios of displacement at the excavation face to the maximum displacement were around 1/3 to 1/2. In general, the weaker the rock mass, the larger the ratio. The displacements in front of the excavation face were decreased with the increasement of distance. At the distance of 1.0 to 1.5 tunnel diameter, the displacements were reduced to one-tenth of the maximum displacement.