• Title/Summary/Keyword: FLAC3D

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Implementation of Barcelona Basic Model into TOUGH2-MP/FLAC3D (TOUGH2-MP/FLAC3D의 Barcelona Basic Model 해석 모듈 개발)

  • Lee, Changsoo;Lee, Jaewon;Kim, Minseop;Kim, Geon Young
    • Tunnel and Underground Space
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    • v.30 no.1
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    • pp.39-62
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    • 2020
  • In this study, Barcelona Basic Model (BBM) was implemented into TOUGH2-MP/FLAC3D for the numerical analysis of coupled thermo-hydro-mechanical (THM) behavior of unsaturated soils and the prediction of long-term behaviors. Similar to the methodology described in a previous study for the implementation of BBM into TOUGH-FLAC, the User Defined Model (UDM) of FLAC based on the Modified Cam Clay Model (MCCM) and the FISH function of FLAC3D were used to extend the existing MCCM module in FLAC3D for the implementation of BBM into TOUGH2-MP/FLAC3D. In the developed BBM module in TOUGH2-MP/FLAC3D, the plastic strains due to change in suction increase (SI) in addition to mean effective stress are calculated. In addition to loading-collapse (LC) yield surface, suction increase (SI) yield surface is changed by hardening rules in the developed BBM module. Several numerical simulations were conducted to verify and validate the implementation of BBM: using an example presented in the FLAC3D manual for the standard MCCM, simulation results using COMSOL, and experimental data presented in SKB Reports. In addition, the developed BBM analysis module was validated by simultaneously performing a series of modeling tests that were performed for the validation of the Quick tools developed for the purpose of effectively deriving BBM parameters, and by comparing the Quick tools and Code_Bright results reported in a previous study.

Numerical modelling of coupled thermo-hydro-mechanical behavior of Heater Experiment-D (HE-D) at Mont Terri rock laboratory in Switzerland (스위스 Mont Terri rock laboratory에서 수행된 암반 히터시험(HE-D)에 대한 열-수리-역학적 복합거동 수치해석)

  • Lee, Changsoo;Choi, Heui-Joo;Kim, Geon-Young
    • Tunnel and Underground Space
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    • v.30 no.3
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    • pp.242-255
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    • 2020
  • The numerical simulations of Heater Experiment-D (HE-D) at the Mont Terri rock laboratory in Switzerland were performed to investigate an applicability of FLAC3D to reproduce the coupled thermo-hydro-mechanical (THM) behaviour in Opalinus Clay, as part of the DECOVLEX-2015 project Task B. To investigate the reliability of numerical simulations of the coupled behaviour using FLAC3D code, the simulation results were compared with the observations from the in-situ experiment, such as temperature at 16 sensors, pore pressure at 6 sensors, and strain at 22 measurement points. An anisotropic heat conduction model, fluid flow model, and transversely isotropic elastic model in FLAC3D successfully represented the coupled thermo-hydraulic behaviour in terms of evolution for temperature and pore pressure, however, performance of the models for mechanical behavior is not satisfactory compared with the measured strain.

Analysis of Hydro-Mechanical Coupling Behavior Considering Excavation Damaged Zone in HLW Repository (고준위방사성폐기물 처분장에서의 굴착손상대를 고려한 수리-역학적 복합거동 해석)

  • Jeewon Lee;Minju Kim;Sangki Kwon
    • Explosives and Blasting
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    • v.41 no.3
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    • pp.38-61
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    • 2023
  • An Excavation Damaged Zone(EDZ) caused by blasting impact changes rock properties, in situ stress distribution, etc., and its effects are noticeable at around a radioactive waste repository located at deep underground. In particular, the increase in permeability due to the formation of cracks may significantly increase the amount of groundwater inflow and the possibility of radioactive nuclide outflow. In this study, FLAC2D and FLAC3D were used to analyze the mechanical and thermal behaviors for three categories: a)No EDZ, b)Uniform EDZ, and c)Random EDZ. It was found that the tunnel displacement in the Random EDZ case was 423% higher than that in the No EDZ case and was 16% higher than that in the Uniform EDZ case. Tunnel inflow in the Random EDZ was also 17.3% and 10.8% higher than that in the No EDZ and the Uniform EDZ case, respectively. The permeability around the tunnel was increased by up to 10 times in the corner of the tunnel wall and roof due to the stress redistribution after excavation. From the computer simulation, it was found that the permeability around the tunnel wall was partially increased but the overall tunnel inflow was decreased with increase of stress ratio. Mechanical analysis using FLAC 3D showed similar results. Slight difference between 2D and 3D could be explained with the development of plastic zone during the advance of tunnel excavation in 3D.

Hydraulic Analysis of a Discontinuous Rock Mass Using Smeared Fracture Model and DFN Model (DFN 모델과 스미어드 균열 모델을 이용한 불연속 암반의 3차원 수리해석)

  • Park, Jungchan;Kim, Jin-Seop;Lee, Changsoo;Kwon, Sangki
    • Tunnel and Underground Space
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    • v.29 no.5
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    • pp.318-331
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    • 2019
  • A three-dimensional(3D) equivalent continuum modeling was performed to analyze hydraulic behavior of rock mass considering discontinuities by using DFN model and smeared fracture model. DFN model was generated by FLAC3D and smeared fracture model was applied by using FISH functions, which is built-in functions in FLAC3D, for equivalent continuum model of fractured rock mass. Comparative analysis with 3DEC, which is for discontinuum analysis, was conducted to verify reliability of equivalent continuum analysis by using FLAC3D. Similar results of hydraulic analysis under the same conditions could be achieved. Equivalent continuum analysis of fractured rock mass by using DFN model was implemented to compare with existing analytical methods for inflow into the tunnel.

Dynamic analyses and field observations on piles in Kolkata city

  • Chatterjee, Kaustav;Choudhury, Deepankar;Rao, Vansittee Dilli;Mukherjee, S.P.
    • Geomechanics and Engineering
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    • v.8 no.3
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    • pp.415-440
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    • 2015
  • In the present case study, High Strain Dynamic Testing of piles is conducted at 3 different locations of Kolkata city of India. The raw field data acquired is analyzed using Pile Driving Analyzer (PDA) and CAPWAP (Case Pile Wave Analysis Programme) computer software and load settlement curves along with variation of force and velocity with time is obtained. A finite difference based numerical software FLAC3D has been used for simulating the field conditions by simulating similar soil-pile models for each case. The net pile displacement and ultimate pile capacity determined from the field tests and estimated by using numerical analyses are compared. It is seen that the ultimate capacity of the pile computed using FLAC3D differs from the field test results by around 9%, thereby indicating the efficiency of FLAC3D as reliable numerical software for analyzing pile foundations subjected to impact loading. Moreover, various parameters like top layers of cohesive soil varying from soft to stiff consistency, pile length, pile diameter, pile impedance and critical height of fall of the hammer have been found to influence both pile displacement and net pile capacity substantially. It may, therefore, be suggested to include the test in relevant IS code of practice.

Coupled Effect of Pile/Slope Systems (억지말뚝-사면의 상호작용 효과)

  • 정상섬;유광호;이선근
    • Journal of the Korean Geotechnical Society
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    • v.19 no.5
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    • pp.163-173
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    • 2003
  • In this paper, a numerical comparison of predictions by limit equilibrium analysis and 3D analysis is presented for slope/pile system. Special attention is given to the coupled analysis based on the explicit finite difference code, FLAC 3D. To this end, an internal routine (FISH) was developed to calculate a factor of safety for a file reinforced slope according to shear strength reduction technique. The case of coupled analyses was performed for stabilizing piles in slope in which the pile response and slope stability are considered simultaneously. In this study, by using these methods, the failure surfaces and factors of safety were compared and analyzed in several cases, such as toe, middle and top of the slope, respectively. Furthermore, the coupled method based on shear strength reduction technique was verified by the comparison with other analysis results.

Analysis on the creep response of bolted rock using bolted burgers model

  • Zhao, Tong-Bin;Zhang, Yu-Bao;Zhang, Qian-Qing;Tan, Yun-Liang
    • Geomechanics and Engineering
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    • v.14 no.2
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    • pp.141-149
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    • 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.

Geomechanical and hydrogeological validation of hydro-mechanical two-way sequential coupling in TOUGH2-FLAC3D linking algorithm with insights into the Mandel, Noordbergum, and Rhade effects

  • Lee, Sungho;Park, Jai-Yong;Kihm, Jung-Hwi;Kim, Jun-Mo
    • Geomechanics and Engineering
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    • v.28 no.5
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    • pp.437-454
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    • 2022
  • The hydro-mechanical (HM) two-way sequential coupling in the TOUGH2-FLAC3D linking algorithm is validated completely and successfully in both M to H and H to M directions, which are initiated by mechanical surface loading for geomechanical validation and hydrological groundwater pumping for hydrogeological validation, respectively. For such complete and successful validation, a TOUGH2-FLAC3D linked numerical model is developed first by adopting the TOUGH2-FLAC3D linking algorithm, which uses the two-way (fixed-stress split) sequential coupling scheme and the implicit backward time stepping method. Two geomechanical and two hydrogeological validation problems are then simulated using the linked numerical model together with basic validation strategies and prerequisites. The second geomechanical and second hydrogeological validation problems are also associated with the Mandel effect and the Noordbergum and Rhade effects, respectively, which are three phenomenally well-known but numerically challenging HM effects. Finally, sequentially coupled numerical solutions are compared with either analytical solutions (verification) or fully coupled numerical solutions (benchmarking). In all the four validation problems, they show almost perfect to extremely or very good agreement. In addition, the second geomechanical validation problem clearly displays the Mandel effect and suggests a proper or minimum geometrical ratio of the height to the width for the rectangular domain to maximize agreement between the numerical and analytical solutions. In the meantime, the second hydrogeological validation problem clearly displays the Noordbergum and Rhade effects and implies that the HM two-way sequential coupling scheme used in the linked numerical model is as rigorous as the HM two-way full coupling scheme used in a fully coupled numerical model.

Fault Reactivation Modeling Using Coupled TOUGH2 and FLAC3D Interface Model: DECOVALEX-2019 Task B (TOUGH2-FLAC3D Interface 모델을 통한 단층 재활성 모델링: DECOVALEX-2019 Task B)

  • Park, Jung-Wook;Park, Eui-Seob;Lee, Changsoo
    • Tunnel and Underground Space
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    • v.30 no.4
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    • pp.335-358
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    • 2020
  • We present a numerical model to simulate coupled hydro-mechanical behavior of fault using TOUGH-FLAC simulator. This study aims to develop a numerical method to estimate fluid injection-induced fault reactivation in low permeability rock and to access the relevant hydro-mechanical stability in rock as part of DECOVALEX-2019 Task B. A coupled fluid flow and mechanical interface model to explicitly represent a fault was suggested and validated from the applications to benchmark simulations and the field experiment at Mont Terri underground laboratory in Switzerland. The pressure build-up, hydraulic aperture evolution, displacement, and stress responses matched those obtained at the site, which indicates the capability of the model to appropriately capture the hydro-mechanical processes in rock fault.

An elasto-plastic damage constitutive model for jointed rock mass with an application

  • Wang, Hanpeng;Li, Yong;Li, Shucai;Zhang, Qingsong;Liu, Jian
    • Geomechanics and Engineering
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    • v.11 no.1
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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.