• Geomechanics and Engineering
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• 제21권4호
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• pp.315-326
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• 2020

The long-term behavior of rockfill material used in the construction of infrastructures such as dams is of great significance. Because of concerns about the application of weak rockfill material in dam construction, further experimental studies on the behavior of these materials are required. In this study, laboratory experiments were performed to investigate the one-dimensional deformation and particle breakage of the weak rockfill material under stress. A one-dimensional compression apparatus was designed and developed for testing of rockfill materials of different maximum particle sizes (MPSs). The compression tests were performed under dry, wet and saturated conditions on samples of rockfill material obtained from a dam construction site in Iran. The results of the experiments conducted at the specimen preparation stage and the 1D compression tests are presented. In weak rockfill, the effect of the addition of water on the behavior of the material was uncertain as there were both an increases and decreases observed in particle breakage. Increasing the MPS of the weak rockfill materials increased particle breakage, which was similar to the behavior of strong rockfill material. In all of the MPSs examined, the settlement of specimens under wet conditions was higher than that observed under dry conditions. Also, the greatest deformation occurred during the first hour of loading.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.846-853
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam with this input parameter. The rockfill material properties for parametric study were obtained from the results of large scale triaxial tests on 34 rockfill materials in the 22 different sites. From the statistical analysis on these data, some statistical characteristics of rockfill material properties such as property range, distribution characteristics, and correlation between the properties were investigated. based on these characteristics, 27 property combinations were constituted by Latin Hypercube sampling method. Dam crest displacements after construction, impounding, and earthquake loading were evaluated by static and dynamic numerical analysis on each combination. From the sensitivity analysis, it was found that the crest displacement of CFR type dam was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the settlement and horizontal displacement of dam crest logarithmically decreased as the shear modulus increased and the difference between the maximum value and the minimum vale amounted to about 9.5 times in case of settlement and about 10 times in case of horizontal displacement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.306-313
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• 2005

For seismic response analysis of rockfill dam, dynamic material properties, by field test, are needed. Density and elastic wave profiles have to be known to get an information of the material properties of structure. In this study, various field tests are applied to the example of rockfill dam to get an information of dynamic material properties and seismic safety is evaluated by seismic response analysis with the result of field tests.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.583-588
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• 2005

In this study, a concrete faced rockfill dam constructed by stages was numerically analyzed, and the numerical results were compared with in situ measurements. The simple incremental elastic and isotropic hyperbolic model was employed to characterize the nonlinear deformation behavior of rockfill material and computational procedure followed construction sequence. A series of large triaxial tests for rockfill material were carried out to obtain mechanical input parameters. According to the analysis results, relative great additional deformation was introduced at the surface of stage-I dam body due to the loading by stage-II construction. The results reveal that numerical analysis can effectively simulate the construction processes, and some meaningful insights about the behavior of CFRD during construction were gained.

• Geomechanics and Engineering
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• 제17권2호
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• pp.119-131
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• 2019

Time dependent creep settlements are one of the most important causes of material deteriorations for the huge water structures such as concrete faced rockfill dams (CFRDs). For this reason, performing creep analyses of CFRDs is vital important for monitoring and evaluating of the future and safety of such dams. In this study, it is observed how changes viscoplastic behaviour of a CFR dam depending the time. Ilısu dam that is the longest concrete faced rockfill dam (1775 m) in the world is selected for the three dimensional (3D) analyses. 3D finite difference model of Ilısu dam is modelled using FLAC3D software based on the finite difference method. Two different special creep material models are considered in the numerical analyses. Wipp-creep viscoplastic material model and burger-creep viscoplastic material model were rarely used for the creep analyses of CFRDs in the last are taken into account for the concrete slab and rockfill materials-foundation, respectively. Moreover, interface elements are defined between the concrete slab-rockfill materials and rockfill materials-foundation to provide interaction condition for 3D model. Firstly, dam and foundation are collapsed under its self-weight and static behaviour of the dam is evaluated for the empty reservoir conditions. Then, reservoir water is modelled considering maximum water level of the dam and time-dependent creep analyses are performed for maximum reservoir condition. In this paper, maximum principal stresses, vertical-horizontal displacements and pore pressures that may occur on the dam body surface during 30 years (from 2017 to 2047) are evaluated in detail. According to numerical analyses, empty and maximum reservoir conditions of Ilısu dam are compared with each other in detail. 4 various nodal points are selected under the concrete slab to better seen viscoplastic behaviour changes of the dam and viscoplastic behaviour differences of these points during 30 years are graphically presented. It is clearly seen that horizontal-vertical displacements and principal stresses for maximum reservoir condition are more than the empty reservoir condition of the dam and significant pore pressures are observed during 30 years for maximum reservoir condition. In addition, horizontal-vertical displacements, principal stresses and pore pressures for 4 nodal points obviously increased until a certain time and changes decreased after this time.

• 한국지반공학회논문집
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• 제24권6호
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• pp.45-55
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• 2008

최근 전 세계적으로 대부분의 댐이 CFRD 형식으로 축조되지만, 일부 지역에서는 지형적 및 환경적 특성으로 인해 석산재를 대신하여 사력재가 댐의 주 축조재료로 이용되고 있다. 최근 국내에서도 사력재를 댐의 주축조재로 이용하도록 댐이 설계된 바 있다. 본 연구에서는 국내 현장에서 채취된 사력재 및 석산재를 대상으로 총 7 case의 대형다짐 및 삼축시험을 수행하였다. 다짐 시험 및 삼축시험을 통해 두 재료의 다짐, 전단 강도, 변형 특성을 산정하였으며, 이로부터 두 재료 사이에 존재하는 특성 차이를 확인하였다. 실험 결과 전단강도에 있어서 사력재가 석산재에 비해 결코 불리하지 않음을 알 수 있었으나, 변형 특성은 다소 차이를 보이고 있었다. 한편 실험 결과를 이용한 댐체 거동해석에서는 주축조 영역에 강성이 큰 사력재를 사용한 경우가 석산재를 사용한 경우에 비해 변형이 작게 발생하였다. 결론적으로 사력재의 강도 및 변형특성이 석산재와는 다소 차이를 보이지만, 석산재를 대신하여 댐의 주축조재료로 사용하여도 안정성에는 큰 문제가 없을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.860-868
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• 2008

Seismic safety analysis of rockfill dams are consist of the stability analysis as an simplifed method and the dynamic analysis as an detailed method. When high risk dams such as Multi-purpose dams were often applied detailed method by dynamic analysis, dynamic properties of dam materials such as shear modulus are considered as most important factor. Dynamic material properties such as shear modulus had to be investigated by cyclic triaxial test et al. during design and construction stage but these were not conducted because of the condition of domestic seismic design technique. MASW and SASW methods had been applied as a non destructive method to investigate dynamic material properties of existing rockfill dam, has no problems in dam safety at present. These methods were usually performed under the assumptions that the subsurface can be described horizontally homogeneous and isotropic layers. Recent studies(Marwin, 1993, Kim, 2001) showed that surface waves generated through inclined structures have different characteristics from those through a horizontally homogeneous layered model. further Kim et al(2005) and Min and Kim(2006) showed that central core type rockfill dam overestimated the shear wave velocities as increasing the depth through the 3D numerical modelling dut to the effect of outer rockfill and geometrical reasons In this study the results of shear wave velocities of seven rockfill dams form comprehensive facility review, was carried out from 2003 to 2007, were collected and analysed to establish the shear wave velocity distribution characteristics in increasing confining stress in rockfill dams and surface wave velocity ranges in rockfill dam through MASW and the limitation in application are discussed to be utilized as an reference value for dynamic analysis.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.351-357
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) subjected to earthquake loading was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam during earthquake loading with this input parameter. From the sensitivity analysis, it was found that the crest displacement of CFR type dam subjected to dynamic loading was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the extent of effect of shear modulus on the displacement at the crest of CFRD due to dynamic loading decreased as maximum amplitude of input acceleration increased.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.818-823
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• 2006

In this study, the suitability of CFGD(concrete faced gravefill dam) was investigated by examining the strength and deformation characteristics of a gravelfill material, a CFGD main fill material, and comparing them with those of several rockfill dam materials. The gravelfill material exhibited similar strength and deformation properties to those of the main fill materials of existing stable large rockfill dams. Since not only CFGD has environmental and economic advantages over CFRD, but its main fill material compares favorably with those of the existing stable CFRDs, CFGD may be the best choice when natural gravel materials are abundant in the vicinity of the dam construction location.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1025-1028
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• 2009

Earth and rock fill dam is our typical dam because of their inherent flexibility and adaptability to various fundation conditions. In order to secure structural safety, rockfill materials are used angular particles obtained by blasting parent rock or rounded particles collected from river beds. Concrete-faces rockfill dams(CFRD) and Concrete-faces gravelfill dams(CFGD) have become popular in the last 20 years as s result of their good performance and low cost compared with the rockfill dam. These Dams are also constructed by the materials. A key factor in the design of the dams is the deformations induced during construction and upon reservoir filling. These can be predicted using the stress-strain and strength properties can be adequately define. However the stress-strain properties of rockfill are difficult to determine because the properties are affected by such factors as particle grading, size and shape of particles, stress conditions, and particle crushing. In our study, testing of the behavior of the rockfill materials are essential prerequisites to the realistic analysis and design of the CFGD. This paper deals with laboratory testing of particle crushing among the study.