• Geomechanics and Engineering
• /
• 제29권1호
• /
• pp.41-51
• /
• 2022

Tunneling in rocks having the time-dependent behavior, causes some difficulties like tunnel convergence and, as a result, pressure on concrete lining; and so instability on this structure. In this paper the time-dependent behaviour of squeezing phenomenon in a large cross section tunnel was investigated as a case study: Alborz tunnel. Then, time-dependent behaviour of Alborz tunnel was evaluated using FLAC2D based on the finite difference numerical method. A Burger-creep viscoelastic model was used in numerical analysis. Using numerical analysis, the long-time effect of squeezing on lining stability was simulated.This study is done for primary lining (for 2 years) and permanent lining (for 100 years), under squeezing situations. The response of lining is discussed base on Thrust Force-Bending Moment and Thrust Force-Shear Force diagrams analysing. The results determined the importance of consideration of time-dependent behaviour of tunnel that structural forces in concrete lining will grow in consider with time pass and after 70 years can cause instability in creepy rock masses section of tunnel. To show the importance of time-dependent behavior consideration of rocks, elastic and Mohr-Coulomb models are evaluated at the end.

• 지질공학
• /
• 제18권4호
• /
• pp.545-553
• /
• 2008

터널 시공 중 막장관찰과 계측자료는 굴착으로 인하여 발생하는 지반 및 주변 구조물의 안정성 평가를 위한 가장 중요한 정보이다. 특히, 발파 굴착으로 이루어지는 NATM 공법에서 막장관찰과 계측은 다음 막장의 굴착 및 지보설계를 위한 핵심자료로 활용이 된다. 하지만, 국내에는 암반분류 결과와 계측결과의 관계에 대한 연구가 많이 부족하여 굴착 및 지보설계에 제대로 활용되지 못하고 있는 실정이다. 본 연구에서는 막장관찰에 의한 암반분류 중 국내외에서 가장 많이 사용되는 RMR 분류법과 내공변위 계측결과의 분석을 통해 지질상태의 변화가 터널의 거동에 미치는 영향을 살펴보고자 하였다. 내공변위의 계측위치와 계측 시점에 따른 변위 측정 편차를 변위 함수를 이용해 보정하였으며, 이를 통해 내공변위의 영향선과 지반조건의 관계를 고찰하였다. 또한 변위 함수 파라미터와 초기변위 발생비율 등 내공변위와 관련된 다양한 요소들의 지반조건에 따른 변화양상을 파악함으로써 막장관찰 및 내공변위 계측을 통한 지반 평가의 기초자료를 제시하고자 하였다.

• 터널과지하공간
• /
• 제3권1호
• /
• pp.80-95
• /
• 1993

Convergence measurements play very important role in the assessment of stability of a tunnel and of the economics of rock reinforcements. The characteristics of convergences are both due to the face advance effect and the time-dependent behaviour of rocks. As the convergence law can be modeled as a specific function of two variables of distance and time, we can determine the type of function and the related parameters from the field measurements. By using the regression method based on the Levengberg-Marquardt algorithm, an analysis of convergence of two different tunnels and one numerical example is described. It is shown that the convergence can be modeled as following function, C(x)=a{1-exp(-bx)} or C(t)=a{1-exp(-bt)} in case of a tunnel excavated in elastic rocks, in case of elasto-plastic or over stressed rocks.

• 한국지반환경공학회 논문집
• /
• 제17권4호
• /
• pp.39-46
• /
• 2016

터널구조물의 안정성 최종평가는 굴착완료 후 현장계측을 수행하여 계측값의 수렴 여부를 통해 판단하는 것이 일반적 평가 기준이다. 본 연구에서는 굴착하는 터널 주변 지반조건이 불량하여 터널 안정성 확보를 위한 보강을 적용한 후 국부적으로 보강구간에서 추가적인 붕락 또는 과다변위가 발생한 터널현장시공 사례의 해석적 방법과 상관성을 분석하였다. 추가 붕락터널에서 붕락유형을 조사해 보면 대부분 천단부 붕락이 발생하고 붕락된 구간에 대한 지질적인 조건을 분석해보면 천단부에서 지표부 인근까지 연장되어 존재하는 단층파쇄대가 존재하는 경우와 상관성이 있는 것으로 분석되었다. 이와같이 단층파쇄대와 같은 지반조건이 터널 천단부에서 지표부 인근까지 연장성을 가지는 경우에는 기존 수치해석적 방법으로 예측한 거동보다 더 큰 거동을 하는 것으로 분석되었다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1998년도 터널.암반역학위원회 박사학위 논문집
• /
• pp.153-204
• /
• 1998

Prediction of lining loads due to tunnelling is one of the major issues to be addressed in the design of a tunnel. The objective of this study is to investigate rational and realistic design loads on tunnel linings. factors influencing the lining load are summarized and discussed. The instruments for measuring the lining loads are reviewed and discussed because field measurements are often necessary to verify the design methods. Tunnel construction in the City of Edmonton has been very active for storm and sanitary purposes. Since the early 1970's, the city has also been developing an underground Light Rail Transit system. The load measurements obtained from these tunnels are compared with the results from the existing design methods. However, none of the existing methods are totally satisfactory, Therefore, there is some room for improvement in the prediction of lining loads. The convergence-confinement method is reviewed and applied to a case history of a tunnel in Edmonton. The convergence curves are obtained from 2-D finite element analyses using three different material models and theoretical equations. The limitation of the convergence-confinement method is discussed by comparing these curves with the field measurements. Three-dimensional finite element analyses are performed to gain a better understanding of stress and displacement behaviour near the tunnel face. An improved design method is proposed based on the review of existing design methods and the performance of numerical analyses. A specific method or combination of two different methods is suggested for the estimation of lining loads for different conditions of tunnelling. A method to determine the stress reduction factor is described. Typical values of dimensionless load factors nD/H for tunnels in Edmonton are obtained from parametric analyses. Finally, the loads calculated using the proposed method are compared with field measurements collected from various tunnels in terms of soil types and construction methods to verify the method. The proposed method gives a reasonable approximation of the lining loads. The proposed method is recommended as an approximate guideline for the design of tunnels, but the results should be confirmed by field measurements due to the uncertainties of the ground and lining properties and the construction procedures, This is the reason that in-situ monitoring should be an integral part of the design procedure.

• Geomechanics and Engineering
• /
• 제14권2호
• /
• pp.141-149
• /
• 2018

In this paper, the creep behavior of bolted rock was analyzed by using the unconfined creep tests and the numerical results. Based on the test results, the Bolted Burgers creep model (B-B model) was proposed to clarify the creep mechanism of rock mass due to rock bolts. As to the simulation of the creep behaviour of bolted rock, a new user-defined incremental iterative format of the B-B model was established and the open-source $FLAC^{3D}$ code was written by using the object-oriented language (C++). To check the reliability of the present B-B creep constitutive model program, a numerical model of a tunnel with buried depth of 1000 m was established to analyze the creep response of the tunnel with the B-B model support, the non-support and the bolt element support. The simulation results show that the present B-B model is consistent with the calculated results of the inherent bolt element in $FLAC^{3D}$, and the convergence deformation can be more effectively controlled when the proposed B-B model is used in the $FLAC^{3D}$ software. The big advantage of the present B-B creep model secondarily developed in the $FLAC^{3D}$ software is the high computational efficiency.

• 터널과지하공간
• /
• 제19권5호
• /
• pp.407-420
• /
• 2009

이 연구에서는 시추 조사와 물리탐사 자료와 같은 다양한 지반 정보를 통합하여 최적의 암반 분류 기법을 도출하는데 지시크리깅을 적용하였다. 최적의 지시크리깅 결과를 얻기 위해서는 효과적으로 hard data(시추조사)와 soft data(물리탐사 자료)를 통합하기 위한 알맞은 방법을 모색할 필요가 있다. 이론적인 베리오그램 모델변수를 결정하기 위해 반복적 비선형 역산 방법을 적용하였고 이 알고리즘의 타당성 검증을 위해 목적함수의 분포양상을 검토한 결과 상관거리에 따른 구배는 대단히 작은 특성을 보였다. 현장 적용지역은 지표에서 터널 계획고까지의 심도가 최대 500 m인 대규모 산악터널 예정지이다. 지시크리깅을 이용하여 soft data인 AMT (Audio frequency Magneto-Telluric) 탐사 자료와 hard data인 RMR자료를 하나로 통합하고자 하였다. 결론적으로 터널계획고와 터널 상부 1D 구간에 대한 암반등급도를 작성하여 도시하였다.