• Geomechanics and Engineering
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• 제11권1호
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• pp.77-94
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• 2016

A forked tunnel, as a special complicated underground structure, is composed of big-arch tunnel, multi-arch tunnel, neighborhood tunnels and separate tunnels according to the different distances between two separate tunnels. Due to the complicated process of design and construction, surrounding jointed rock mass stability of the big-arch tunnel which belongs to the forked tunnel during excavation is a hot issue that needs special attentions. In this paper, an elasto-plastic damage constitutive model for jointed rock mass is proposed based on the coupling method considering elasto-plastic and damage theories, and the irreversible thermodynamics theory. Based on this elasto-plastic damage constitutive model, a three dimensional elasto-plastic damage finite element code (D-FEM) is implemented using Visual Fortran language, which can numerically simulate the whole excavation process of underground project and perform the structural stability of the surrounding rock mass. Comparing with a popular commercial computer code, three dimensional fast Lagrangian analysis of continua (FLAC3D), this D-FEM has advantages in terms of rapid computing process, element grouping function and providing more material models. After that, FLAC3D and D-FEM are simultaneously used to perform the structural stability analysis of the surrounding rock mass in the forked tunnel considering three different computing schemes. The final numerical results behave almost consistent using both FLAC3D and D-FEM. But from the point of numerically obtained damage softening areas, the numerical results obtained by D-FEM more closely approach the practical behaviors of in-situ surrounding rock mass.

• 한국지반공학회논문집
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• 제19권2호
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• pp.147-157
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• 2003

사면이나 터널과 같은 암반 구조물의 안정성에 영향을 미치는 절리면은 크게 절리면의 상태(돌기 강도, 충전재, 돌기 경사)와 주위 암반에 의해 구속되는 경계조건에 따라 지배된다. 본 연구에서는 암반 구조물에 작용하는 경계조건 과 절리상태에 따른 전단특성을 규명하기 위하여 PID 알고리즘에 의해 서보제어가 되는 절리면 전단시험 장비를 개발하였다. 그리고 돌기 경사가 일정한 톱니형 형상의 절리면에 대하여 일련의 실험을 수행하여 시험장비의 제어성능을 확인하고 사면이나 터널과 같이 경계조건이 다른 암반구조물에서는 전단강도 평가기법을 달리하여야 함을 알 수 있었다.

• 터널과지하공간
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• 제4권3호
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• pp.215-227
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• 1994

Rock Mass classifications have been developed in many European countries. The most widely used classification methods are the Rock Mass Rating (RMR) system proposed by Bieniawski(1973) and the Q-system developed By Barton et al. (1974). These methods are also adopted at many mountain tunnels and subway sites in our country. Here, a geomechanical classification for slopeds in rock, the "Slope Mass Rating"(SMR) is presented for the preliminary assessment of slope stabiliyt. This method can be applied to excavation and support design in the front part of tunnel and cutting area as a guide line and recommendation on support methods which allow a systemmetic use of geomechanical classification for rock slopes.

• 터널과지하공간
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• 제20권5호
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• pp.352-359
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• 2010

병설터널에서 근접 굴착으로 인한 영향은 터널간 이격거리에 따라 달라진다. 본 논문에서는 수평절리암반에 형성된 병설터널의 이격거리에 따른 영향을 파악하기 위하여 콘크리트 블록으로 균일 수평 절리 모형 지반을 조성하고 이격거리를 변화시키면서 모형터널을 설치한 후에 대형 모형실험을 수행하였다. 병설터널의 이격거리(필라폭)는 터널 폭 D를 기준으로 0.29D, 0.59D, 0.88D, 1.18D로 변화시켰다. 실험중에 필라 응력, 터널변위, 지반 변위를 계측하였다. 측압계수는 1.0을 유지하였다. 실험결과, 터널 및 주변지반의 변위와 필라 응력은 필라 폭이 감소함에 따라 증가하였다. 각 계측항목에서 최대 변화폭이 발생하는 단계는 후행터널의 상반굴착 직후로 나타났다. 병설터널 굴착 시 가장 큰 영향을 받는 위치는 필라부와 맞닿아 있는 선행터널의 어깨부로 확인되었다. 이러한 결과는 병설터널의 안정성은 시공 시 천단변위보다 내공변위 관리를 통해 평가되어야 한다는 것을 보여준다. 또한, 병설터널의 영향권이 양호한 지반조건에 대한 경험이론의 근접시공 영향권(0.8D~2.0D)보다 근접한 0.59D~0.88D 범위에서 형성되었으며 이러한 영향범위 감소는 병설터널의 안정성에 수평절리의 영향이 있는 것으로 판단된다.

• 터널과지하공간
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• 제25권5호
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• pp.423-434
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• 2015

본 연구에서는 필러 폭과 모형재료의 강도가 서로 다른 등방성 및 이방성 암반 내 쌍굴터널의 모형실험을 통해 얻어진 터널의 변형과 필러부 균열이 발생한 이축압력 자료를 이용하여 터널 간 이격거리, 지반 강도, 등방성 및 이방성이 터널 안정성에 미치는 영향을 알아보았다. 모형재료의 일축압축강도에 대한 균열개시압력의 백분율을 균열개시압력비율이라고 정의할 경우, 강도가 큰 지반에 시공되는 쌍굴터널은 강도가 작은 지반에 비하여 균열개시압력 값은 크지만, 균열개시압력비율은 작게 나타났다. 이에 비해 필러 폭이 큰 쌍굴터널은 필러 폭이 작은 경우에 비하여 균열개시압력 값이 클 뿐 아니라 균열개시압력비율도 크게 나타나, 필러 폭은 쌍굴터널 안정성에 영향을 미치는 주된 요소로 판단된다. 지반의 등방성과 이방성 여부도 터널 안정성에 영향을 미쳤는데, 이방성 모형은 등방성 모형에 비해 균열개시압력과 균열개시압력비율이 작을 뿐 아니라 필러부에 존재한 기존 불연속면을 따라 균열이 발생하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1500-1505
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• 2010

The objective of this study is controlling of the large diameter Shield TBM excavation for subway tunnels. In this paper, it will focus on the selection of Shield TBM and the problems of excavation due to unusual abrasion of the Disk Cutters and the distorted Cutter Mounts, in mixed layer of soil in below and hard rock in above, and in rock layer. And also, it will be discussed that the type of ground improvement to change and repair the Disk Cutters and the distorted Cutter Mounts, Advance Rate, Cutter Torque, etc. The results of this study will be using controlling of the excavation in various large diameter Shield TBM for subway tunnels.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.248-255
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• 2006

Among a variety of influencing components, time-variant seepage and long-term underground motion are important to understand the abnormal behavior of tunnels. Excessiveness of these two components could be the direct cause of severe damage on tunnels. however, it is not easy to quantify the effect of these on the behavior of tunnels. These parameters can be estimated by using inverse methods once the appropriate relationship between inputs and results are clarified. Various inverse methods or parameter estimation techniques such as artificial neural network and least square method can be used depending on the characteristics of given problems. Numerical analyses, experiments, or monitoring results are frequently used to prepare a set of inputs and results to establish the back analysis models. In this study, a back analysis method has been developed to estimate geotechnically hard-to-known parameters such as permeability of tunnel filter, underground water table, long-term rock mass load, size of damaged zone associated with seepage and long-term underground motion. The artificial neural network technique is adopted and the numerical models developed in the firstpart are used to prepare a set of data for learning process. Tunnel behavior especially the displacements of the lining has been exclusively investigated for the back analysis.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2007년도 특별심포지엄 논문집
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• pp.63-79
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• 2007

Several remedial works were attempted to stabilize the collapsed area of the inlet slopes of diversion tunnel, but prevention of any further movement was being only carried out at beginning stage by filling the area with aggregates and rock debris, after several cracks had been initiated and developed around the area. The extra specialty developed folding zone is consisted with highly weathered Greywacke and Black shale. The suggested solution is to improve the properties of the rock mass of failed area by choosing the optimum level of reinforcement through the increment of slope rock support design so as to control the movement of slopes during the re-excavation. The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia. The power station will consist of a 210m height Concrete Faced Rockfill Dam. During the construction of the dam and the power facilities the Balui River has to be diverted of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four defined Rock Mass Type (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each "global" slope without any rock support and shotcrete system. In the second stage, it is calculated for each "local" slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• 터널과지하공간
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• 제8권4호
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• pp.296-306
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• 1998

바쿤 수력발전 공사계획은 대형댐과 2,520 MW 출력량의 수력발전소를 건설하는 대형 턴키 프로젝트이며 현재는 발전댐 건설에 앞서 3개의 가베수 터널이 시공중에 있다. 바쿤 지역은 유기물 함량이 높아 쉽게 부서지는 퇴적지층으로 이러한 열대우림지역에서 가배수로 터널의 지보설계를 위해 전체적인 암층단위를 공학적인 목적과 역학적 거동양상을 토대로 주도적인 암종에 따라 분류하였다. 또한 이러한 암층단위를 기준으로 풍화정도와 절리의 빈도 및 특성을 고려하여 다시 4개의 암반유형으로 분류하였고 또한 가배수로 터널의 특성과 현재의 지반특성과 현재의 지반특성을 고려하여 지반내 swelling 광물의 존재를 확인하였다. 다양한 암반과 지보조건에 적합한 다양한 Swellex 록볼트를 적용하였으며 지지력이 낮은 록볼트를 사용할 대 발생되는 문제는 볼트의 면적에 따른 록볼트의 양을 조절하여 해결하였다. 또한 계측결과와 전산해석 결과에 따라 지보재의 설치간격, 수량을 조절하였으며, 계측결과에 따른 역해석을 실시하여 최적의 지보패턴을 결정하였다.

• Geomechanics and Engineering
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• 제31권3호
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• pp.265-279
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• 2022

Tunnel convergence prediction is essential for the safe construction and design of tunnels. This study proposes five machine learning models of deep neural network (DNN), K-nearest neighbors (KNN), Gaussian process regression (GPR), support vector regression (SVR), and decision trees (DT) to predict the convergence phenomenon during or shortly after the excavation of tunnels. In this respect, a database including 650 datasets (440 for training, 110 for validation, and 100 for test) was gathered from the previously constructed tunnels. In the database, 12 effective parameters on the tunnel convergence and a target of tunnel wall convergence were considered. Both 5-fold and hold-out cross validation methods were used to analyze the predicted outcomes in the ML models. Finally, the DNN method was proposed as the most robust model. Also, to assess each parameter's contribution to the prediction problem, the backward selection method was used. The results showed that the highest and lowest impact parameters for tunnel convergence are tunnel depth and tunnel width, respectively.