• Title/Summary/Keyword: Distinct-element method

Search Result 146, Processing Time 0.021 seconds

Field Investigation and Stability Analysis of a Volcanic Rock Slope at the Song-Gok site, Wan-Do (완도 송곡지구 화산암류 비탈면의 현장조사 및 안정성 검토 사례 연구)

  • Kim, Hong-Gyun;Ok, Young-Seok;Kim, Seung-Hyun;Koo, Ho-Bon
    • The Journal of Engineering Geology
    • /
    • v.23 no.2
    • /
    • pp.149-160
    • /
    • 2013
  • Volcanic activity commonly creates a highly complicated volcanic complex due to the admixture of lava flow and sedimentation of volcanic ash. The Song-Gok site is composed of volcanic rocks that collapsed at the lower part of the slope, in combination with several discontinuities in and around a fault. The results of projection analysis indicated the possibility of plane, wedge, and toppling failure in the failure section. The results of discontinuity modeling using the Distinct Element Method (DEM) revealed a total displacement of 207 mm and a joint shear displacement of 114 mm. The yield surface zone was verified at the fault plane of the failure section. In geotechnical terms, volcanic rock slopes are characteristically vulnerable to failure because of differential weathering among the various rock types, the effect of groundwater based on the permeability of the rocks, and the presence of systematic joints generated by the cooling and contraction of lava. When considering the stability of a volcanic rock slope, it is necessary to consider data such as the geological features of the rock, as obtained through detailed geological survey, and variations in discontinuities and rock blocks.

Analysis on the Deformation Characteristics of a Pillar between Large Caverns by Burton-Bandis Rock Joint Model (Barton-Bandis 절리 모델에 의한 지하대공동 암주의 변형 특성 연구)

  • 강추원;임한욱;김치환
    • Tunnel and Underground Space
    • /
    • v.11 no.2
    • /
    • pp.109-119
    • /
    • 2001
  • Up to now single large cavern was excavated for each undergroud hydraulic powerhouse in Korea. But the Yangyang underground hydraulic powerhouse consists of two large caverns; a powerhouse cavern and main transformer cavern. In this carte, the structural stability of the caverns, especially the rock pillar formed between two large caverns, should be guaranteed to be sound to make the caverns permanently sustainable. In this research, the Distinct Element Method(DEM) was used to analyze the structural stability of two caverns and the rock pillar. The Barton-Bandis joint model was used as a constitutive model. The moot significant parameters such as in-site stress, JRC of in-situ natural joints, and spatial distribution characteristics of discontinuities were acquired through field investigation. In addition, two different cases; 1) with no support system and 2) with a support system, were analysed to optimize a support system and to investigate reinforcing effects of a support system. The results of analysis horizontal displacement and joint shear displacement proved to be reduced with the support system. The relaxed zone in the rock pilar also proved to be reduced in conjunction with the support system. Having a support system in place provided the fact that the non zero minimum principal stresses were still acting in the rock pillar so that the pillar was not under uniaxial compressive condition but under triaxial compressive condition. The structural stability f an approximately 36 m wide rock pillar between two large caverns was assured with the appropriate support system.

  • PDF

A Study of Blasting Demolition by Scaled Model Test and PEC2D Analysis (축소모형실험 및 PFC2D해석에 따른 발파해체 거동분석)

  • 채희문;전석원
    • Tunnel and Underground Space
    • /
    • v.14 no.1
    • /
    • pp.54-68
    • /
    • 2004
  • In this study, scaled model tests were performed on blasting demolition of reinforced concrete structures and the experimental results were analyzed in comparison with the results of numerical analysis. The tests were designed to induce a progressive collapse, and physical properties of the scaled model were determined using scale factors obtained ken dimension analysis. The scaled model structure was made of a mixture of plaster, sand and water at the ratio determined to yield the best scaled-down strength. Lead wire was used as a substitute for reinforcing bars. The scaled length was at the ratio of 1/10. Selecting the material and scaled factors was aimed at obtaining appropriately scaled-down strength. PFC2D (Particle Flow Code 2-Dimension) employing DEM (Distinct Element Method) was used for the numerical analysis. Blasting demolition of scaled 3-D plain concrete laymen structure was filmed and compared to results of numerical simulation. Despite the limits of 2-D simulation the resulting demolition behaviors were similar to each other. Based on the above experimental results in combination with bending test results of RC beam, numerical analysis was carried out to determine the blasting sequence and delay times. Scaled model test of RC structure resulted in remarkably similar collapse with the numerical results up to 900㎳ (mili-second).

Effect of Joint Geometry on Anisotropic Deformability of Jointed Rock Masses (절리의 기하학적 속성이 절리성 암반의 이방적 변형 특성에 미치는 영향)

  • Ryu, Seongjin;Um, Jeong-Gi
    • Economic and Environmental Geology
    • /
    • v.53 no.3
    • /
    • pp.271-285
    • /
    • 2020
  • In this study, a numerical experiment related to the stress-strain analysis was performed on 3-D discrete fracture network(DFN) systems based on the distinct element method to evaluate the effect of joint geometry on deformability of jointed rock masses. Using one or two joint sets with deterministic orientation, a total of 12 3-D DFN blocks having 10m cube domain were generated with different joint density and size distribution. Directional deformation modulus of the DFN cube blocks were estimated along the axis directions of 3-D cartesian coordinate. In addition, deviatoric stress directions were chosen at every 30° of trend and plunge in 3-D for some DFN blocks to examine the variability of directional deformation modulus with respect to joint geometry. The directional deformation modulus of the DFN block were found to reduce with the increase of joint size distribution. The increase in joint density was less likely to have a significant effect on directional deformation modulus of the DFN block in case of the effect of rock bridges was relatively large because of short joint size distribution. It, however, was evaluated that the longer the joint size, the increase in the joint density had a more significant effect on the anisotropic deformation modulus of the DFN block. The variation of the anisotropic deformation modulus according to the variations in joint density and size distribution was highly dependent on the number of joint sets and their orientation in the DFN block. Finally, this study addressed a numerical procedure for stress-strain analysis of jointed rock masses considering joint geometry and discussed a methodology for practical application at the field scale.

Estimation of Mechanical Representative Elementary Volume and Deformability for Cretaceous Granitic Rock Mass: A Case Study of the Gyeongsang Basin, Korea (경상분지 백악기 화강암 암반에 대한 역학적 REV 및 변형특성 추정사례)

  • Um, Jeong-Gi;Ryu, Seongjin
    • The Journal of Engineering Geology
    • /
    • v.32 no.1
    • /
    • pp.59-72
    • /
    • 2022
  • This study employed a 3-D numerical analysis based on the distinct element method to estimate the strength and deformability of a Cretaceous biotite granitic rock mass at Gijang, Busan, Korea. A workflow was proposed to evaluate the scale effect and the representative elementary volume (REV) of mechanical properties for fractured rock masses. Directional strength and deformability parameters such as block strength, deformation modulus, shear modulus, and bulk modulus were estimated for a discrete fracture network (DFN) in a cubic block the size of the REV. The size of the mechanical REV for fractured rock masses in the study area was determined to be a 15 m cube. The mean block strength and mean deformation modulus of the DFN cube block were found to be 52.8% and 57.7% of the intact rock's strength and Young's modulus, respectively. A constitutive model was derived for the study area that describes the linear-elastic and orthotropic mechanical behavior of the rock mass. The model is expected to help evaluate the stability of tunnels and underground spaces through equivalent continuum analysis.

Effects of macroporosity and double porosity on noise control of acoustic cavity

  • Sujatha, C.;Kore, Shantanu S.
    • Advances in aircraft and spacecraft science
    • /
    • v.3 no.3
    • /
    • pp.351-366
    • /
    • 2016
  • Macroperforations improve the sound absorption performance of porous materials in acoustic cavities and in waveguides. In an acoustic cavity, enhanced noise reduction is achieved using porous materials having macroperforations. Double porosity materials are obtained by filling these macroperforations with different poroelastic materials having distinct physical properties. The locations of macroperforations in porous layers can be chosen based on cavity mode shapes. In this paper, the effect of variation of macroporosity and double porosity in porous materials on noise reduction in an acoustic cavity is presented. This analysis is done keeping each perforation size constant. Macroporosity of a porous material is the fraction of area covered by macro holes over the entire porous layer. The number of macroperforations decides macroporosity value. The system under investigation is an acoustic cavity having a layer of poroelastic material rigidly attached on one side and excited by an internal point source. The overall sound pressure level (SPL) inside the cavity coupled with porous layer is calculated using mixed displacement-pressure finite element formulation based on Biot-Allard theory. A 32 node, cubic polynomial brick element is used for discretization of both the cavity and the porous layer. The overall SPL in the cavity lined with porous layer is calculated for various macroporosities ranging from 0.05 to 0.4. The results show that variation in macroporosity of the porous layer affects the overall SPL inside the cavity. This variation in macroporosity is based on the cavity mode shapes. The optimum range of macroporosities in poroelastic layer is determined from this analysis. Next, SPL is calculated considering periodic and nodal line based optimum macroporosity. The corresponding results show that locations of macroperforations based on mode shapes of the acoustic cavity yield better noise reduction compared to those based on nodal lines or periodic macroperforations in poroelastic material layer. Finally, the effectiveness of double porosity materials in terms of overall sound pressure level, compared to equivolume double layer poroelastic materials is investigated; for this the double porosity material is obtained by filling the macroperforations based on mode shapes of the acoustic cavity.

DISCRETE PARTICLE SIMULATION OF DENSE PHASE PARTICULATE FLOWS

  • Tsuji Y.
    • 한국전산유체공학회:학술대회논문집
    • /
    • 2005.10a
    • /
    • pp.11-19
    • /
    • 2005
  • First, methods of numerical analysis of gas-particle flows is classified into micro, meso and macro scale approaches based on the concept of multi-scale mechanics. Next, the explanation moves on to discrete particle simulation where motion of individual particles is calculated numerically using the Newtonian equations of motion. The author focuses on the cases where particle-to-particle interaction has significant effects on the phenomena. Concerning the particle-to-particle interaction, two cases are considered: the one is collision-dominated flows and the other is the contact-dominated flows. To treat this interaction mathematically, techniques named DEM(Distinct Element Method) or DSMC (Direct Simulation Monte Carlo) have been developed DEM, which has been developed in the field of soil mechanics, is useful for the contact -dominated flows and DSMC method, developed in molecular gas flows, is for the collision-dominated flows. Combining DEM or DSMC with CFD (computer fluid dynamics), the discrete particle simulation becomes a more practical tool for industrial flows because not only the particle-particle interaction but particle-fluid interaction can be handled. As examples of simulations, various results are shown, such as hopper flows, particle segregation phenomena, particle mixing in a rotating drum, dense phase pneumatic conveying, spouted bed, dense phase fluidized bed, fast circulating fluidized bed and so on.

  • PDF

Dipole Distributions on a Hyperboloidal Panel (쌍곡면 패널에의 다이폴 분포)

  • Chang-Sup Lee;Jung-Chun Suh
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.32 no.2
    • /
    • pp.32-42
    • /
    • 1995
  • When the thickness becomes so small as in the case of the trailing edge of the propeller blade or when the curvature of the surface varies rapidly as in ship stem, the existing panel method employing a flat-surface panel, obtained by collapsing the original non-planar surface into its mean location, suffers the leakage problem and also gives inaccurate induction upon the field point very close to the panel. The hyperboloidal panel deals with the induction from the dipole distributed on the non-planar surface without approximation, overcoming the defects of the flat-surface panel. This paper introduces two distinct derivations of the formulae to compute the integral for the potential induced by a dipole of uniform density distributed on a non-planar hyperboloidal surface element. One method is based on the Gauss-Bonnet theorem and the other is based on the transformation of the surface integral into a line integral.

  • PDF

Assessment of Blast-induced Vibration for the Stability of Discontinuous Rock Mass (암반절리를 고려한 발파진동 영향평가)

  • Park, Byung-Ki;Jeon, Seok-Won;Park, Gwang-Jun;Do, Deog-Soo;Kim, Tae-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2005.11a
    • /
    • pp.485-492
    • /
    • 2005
  • Since blast-induced vibration may cause serious problem to the rock mass as well as the nearby structures, the prediction of blast-induced vibration and the stability evaluation must be performed before blasting activities. Dynamic analysis has been Increased recently in order to analyze the effect of the blast-induced vibration. Most of the previous studies, however, were based on the continuum analysis unable to consider rock joints which significantly affect the wave propagation and attenuation characteristics. They also adopted pressure curves estimated by theoretical or empirical equations as input detonation load, thus there were very difficult to reflect the characteristics of propagating media. In this study, therefore, we suggested a discontinuum dynamic analysis technique which uses velocity waveform obtained from a test blast as an input detonation load. A distinct element program, UDEC was used to consider the effect of rock joints. In order to verify the validity of proposed method, the test blast was simulated. The predicted results from the proposed method showed a good agreement with the measured vibration data from the test blast Through the dynamic numerical modelling on the planned road tunnel and slope, we evaluated the effect of blast-induced vibration and the stability of rock slope.

Effect of Deformation Zones on the State of In Situ Stress at a Candidate Site of Geological Repository of Nuclear Waste in Sweden (스웨덴 방사성 폐기물 처분장 후보부지의 사례를 통해 살펴본 대규모 변형대가 암반의 초기응력에 미치는 영향)

  • Min, Ki-Bok
    • Tunnel and Underground Space
    • /
    • v.18 no.2
    • /
    • pp.134-148
    • /
    • 2008
  • The state of in situ stress is an important factor in considering the suitability of a site as a geological repository for nuclear waste. In this study, three-dimensional distinct numerical analysis was conducted to investigate the effect of deformation zones on the state of stress in the Oskarshamn area, which is one of two candidate sites in Sweden. A discontinuum numerical model was constructed by explicitly representing the numerous deformation zones identified from site investigation and far-field tectonic stress was applied in the constructed model. The numerical model successfully captured the variation of measured stress often observed in the rock mass containing large-scale fractures, which shows that numerical analysis can be an effective tool in improving the understanding of the state of stresses. Discrepancies between measured and modelled stress are attributed to the inconsistent quality of measured stress, uncertainty in geological geometry. and input data for fractures.