• Title/Summary/Keyword: soil model

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Development of a New Pressure-Sinkage Model for Rover Wheel-Lunar Soil Interaction based on Dimensional Analysis and Bevameter Tests

  • Lim, Yujin;Le, Viet Dinh;Bahati, Pierre Anthyme
    • Journal of Astronomy and Space Sciences
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    • v.38 no.4
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    • pp.237-250
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    • 2021
  • A rover is a planetary surface exploration device designed to move across the ground on a planet or a planetary-like body. Exploration rovers are increasingly becoming a vital part of the search for scientific evidence and discoveries on a planetary satellite of the Sun, such as the Moon or Mars. Reliable behavior and predictable locomotion of a rover is important. Understanding soil behavior and its interaction with rover wheels-the terramechanics-is of great importance in rover exploration performance. Up to now, many researchers have adopted Bekker's semiempirical model to predict rover wheelsoil interaction, which is based on the assumption that soil is deformable when a pressure is applied to it. Despite this basic assumption of the model, the pressure-sinkage relation is not fully understood, and it continues to present challenges for rover designers. This article presents a new pressure-sinkage model based on dimensional analysis (DA) and results of bevameter tests. DA was applied to the test results in order to propose a new pressure-sinkage model by reducing physical quantitative parameters. As part of the work, a new bevameter was designed and built so that it could be successfully used to obtain a proper pressure-sinkage relation of Korean Lunar Soil Simulant (KLS-1). The new pressure-sinkage model was constructed by using three different sizes of flat plate diameters of the bevameter. The newly proposed model was compared successfully with other models for validation purposes.

Prediction of Landslide Probability around Railway using Decision Tree Model (Decision Tree model을 이용한 철도 주변 산사태 발생가능성 예측)

  • Yun, Jung-Mann;Song, Young-Suk;Bak, Gueon Jun;You, Seung-Kyong
    • Journal of the Korean Geosynthetics Society
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    • v.16 no.4
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    • pp.129-137
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    • 2017
  • In this study, the prediction of landslide probability was performed to the study area located in ${\bigcirc}{\bigcirc}$ area of Muan-gun, Jeonnam Province around Honam railway using the computer program SHAPP ver 1.0 developed by a decision tree model. The soil samples were collected at total 8 points, and soil tests were performed to measure soil properties. The thematic maps of soil properties such as coefficient of permeability and void ratio were made on the basis of soil test results. The slope angle analysis of topography was performed using a digital map. As the prediction result of landslide probability, 435 cells among total 15,552 cells were predicted to be in the event of landslides. Therefore, the predicted area of occurring landslides may be $43,500m^2$ because the analyzed cell size was $10m{\times}10m$.

Soil Stress-Deformation Analysis by Elasto-Plastic Model and Elasto-Viscoplastic Model - Using Back Analysis Method - (탄소성모델과 탄점소성모델을 이용한 지반변형해석 - 역해석 기법의 적용 -)

  • Kwon, Ho Jin;Song, Young Woo;Lee, Won Taek;Byun, Kwang Wook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.4
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    • pp.199-208
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    • 1993
  • Using several soil parameters which are obtained from the PI-experimental formulas and the back analysis method, the elastic analysis, the elasto-plastic analysis and the elasto-viscoplastic analysis for soil deformation are executed. Comparing the results with those of consolidation test, the indirect estimation method for soil parameters and the suitability of constitutive models are studied. The elastic analysis using back analysis result and the elasto-plastic analysis using the perconsolidation test. The elasto-viscoplastic analysis disagrees with the results of meability coefficient obtained from back analysis are the nearest to the results of the consolidation test. It is inferred that elasto-viscoplastic model is not adequate to the soil of which plasticity index is low.

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Parametric Analysis on Ultimate Behavior of Cylindrical GFRP Septic Tank (원통형 GFRP 개인하수 처리시설의 극한거동에 대한 매개변수해석)

  • Kim, Sung Bo;Cho, Kwang Je
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.4
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    • pp.1337-1347
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    • 2013
  • The parametric analysis on ultimate behavior of buried cylindrical GFRP(Glass Fiber Reinforced Polymer) septic tank was presented. Two kinds of F.E. analysis model(soil-spring model and 3D full model) was constructed. The ultimate behavior of septic tank was investigated according to the size of stiffened steel ring and properties of underground soil. Ramberg-Osgood model and Druker-Prager model were used for material nonlinear characteristics of GFRP septic tank and soil, respectively. The diameter and thickness of stiffened steel ring inside septic tank, elastic modulus and internal friction angle of soil were selected for parametric variables. The ultimate behavior of septic tank, load-displacement, axial and hoop strain, were calculated and investigated.

Crack Propagation in Earth Embankment Subjected to Fault Movement (단층 운동시 댐 파괴 거동 해석)

  • 손익준
    • Proceedings of the Korean Geotechical Society Conference
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    • 1988.06c
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    • pp.3-67
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    • 1988
  • Model studies on the response of homgeneous earth embankment dams subjected to strike-slip fault movement have been penomed via centrifuge and finite element analysis. The centrifuge model tests have shown that crack development in earth embankment experiences two major patters: shear failure deep inside the embankment and tension failure near the surface. The shear rupture zone develops from the base level and propagates upward continuously in the transverse direction but allows no open leakage chnnel. The open tensile cracks develop near the surface of the embankment, but they disappear deep in the embankment. The functional relationship has been developed based on the results of the centrifuge model tests incorporating tile variables of amount of fault movement, embankment geometry, and crack propagation extent in earth des. This set of information can be used as a guide line to evaluate a "transient" safety of the duaged embankment subjected to strike-slip fault movement. The finite element analysis has supplemented the additional expluations on crack development behavior identified from the results of the centrifuge model tests. The bounding surface time-independent plasticity soil model was employed in the numerical analysis. Due to the assumption of continuum in the current version of the 3-D FEM code, the prediction of the soil structure response beyond the failure condition was not quantitatively accurate. However, the fundamental mechanism of crack development was qualitatively evaluated based on the stress analysis for the deformed soil elements of the damaged earth embankment. The tensile failure zone is identified when the minor principal stress of the deformed soil elements less than zero. The shear failure zone is identified when the stress state of the deformed soil elements is at the point where the critical state line intersects the bounding surface.g surface.

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FEM-based modelling of stabilized fibrous peat by end-bearing cement deep mixing columns

  • Dehghanbanadaki, Ali;Motamedi, Shervin;Ahmad, Kamarudin
    • Geomechanics and Engineering
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    • v.20 no.1
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    • pp.75-86
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    • 2020
  • This study aims to simulate the stabilization process of fibrous peat samples using end-bearing Cement Deep Mixing (CDM) columns by three area improvement ratios of 13.1% (TS-2), 19.6% (TS-3) and 26.2% (TS-3). It also focuses on the determination of approximate stress distribution between CDM columns and untreated fibrous peat soil. First, fibrous peat samples were mechanically stabilized using CDM columns of different area improvement ratio. Further, the ultimate bearing capacity of a rectangular foundation rested on the stabilized peat was calculated in stress-controlled condition. Then, this process was simulated via a FEM-based model using Plaxis 3-D foundation and the numerical modelling results were compared with experimental findings. In the numerical modelling stage, the behaviour of fibrous peat was simulated based on hardening soil (HS) model and Mohr-Coulomb (MC) model, while embedded pile element was utilized for CDM columns. The results indicated that in case of untreated peat HS model could predict the behaviour of fibrous peat better than MC model. The comparison between experimental and numerical investigations showed that the stress distribution between soil (S) and CDM columns (C) were 81%C-19%S (TS-2), 83%C-17%S (TS-3) and 89%C-11%S (TS-4), respectively. This implies that when the area improvement ratio is increased, the share of the CDM columns from final load was increased. Finally, the calculated bearing capacity factors were compared with results on the account of empirical design methods.

Characteristics of Vertical Stress Distribution in Soil according to the Relative Density of Sandy Soil in case of Surface Loading (지표면 재하시 사질토 지반의 상대밀도에 따른 지중 연직응력분포 특성)

  • 임종석;이인형;정원중
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.422-426
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    • 2003
  • Model soil tank tests were conducted in sandy soil to investigate the effect of surcharge strip loads on vertical stress distribution in soil. A total number of 6 tests were performed using one loading plate and two relative density(55%, 65%). The soil was considered as an elastic material, while no friction was allowed between the wall and the soil. Measured stress values were compared to predictions defined by Frohlich, Boussinesq and Westergaard. The comparison of measured values and predictions used the ratio between the soil pressure and load value. Results of this study demonstrated that experimental values were generally larger than predictions. The Frohlich analysis provided the best prediction, while the Boussinesq analysis and Westergaard theory not presented a satisfactional result.

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Dynamic Analysis of Soil-Structure System Considering Characteristics of Structure and Complicated Soil Profile (구조물과 복잡한 지층 특성을 고려한 지반-구조물 시스템의 동적 해석)

  • Park, Jang-Ho
    • Journal of the Korean Society of Safety
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    • v.22 no.5
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    • pp.50-56
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    • 2007
  • In the past, a number of approaches, such as analytical, numerical or experimental methods, have been developed to deal with the soil-structure interaction effects. However, for many problems with complex geometry and material discontinuity most of approaches are nearly unpractical since it is difficult to model structures and complicated soil profiles precisely. This paper presents a soil-structure interaction analysis approach, which carl consider precisely characteristics of structures and complicated soil profiles. The presented approach overcomes the difficulties by adopting an unaligned mesh generation approach. From numerical examples, the applicability of the proposed approach is validated and dynamic responses of soil-structure systems subjected to earthquake loading are investigated considering characteristics of structures and complicated soil profiles.

Numerical study on the effect of crack network representation on water content in cracked soil

  • Krisnanto, Sugeng;Rahardjo, Harianto;Leong, Eng Choon
    • Geomechanics and Engineering
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    • v.21 no.6
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    • pp.537-549
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    • 2020
  • The presence of cracks changes the water content pattern during seepage through a cracked soil as compared to that of intact soil. In addition, several different crack networks may form in one soil type. These two factors result in a variation of water contents in the soil matrix part of a cracked soil during seepage. This paper presents an investigation of the effect of crack network representation on the water content of the soil matrix part of cracked soil using numerical models. A new method for the numerical generation of crack networks incorporating connections among crack endpoints was developed as part of the investigation. Numerical analysis results indicated that the difference in the point water content was large, whereas the difference in the average water content was relatively small, indicating the uniqueness of the crack network representation on the average water content of the soil matrix part of cracked soil.

The Estimation of Soil Loss in the Buffer Zone of Guem River using a Simulation of Future Climate Change (미래기후변화를 반영한 금강 수변 구역에서의 표토 유실량 예측)

  • Lee, Dal-Heui;Chung, Sung-Lae
    • Journal of Soil and Groundwater Environment
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    • v.19 no.6
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    • pp.30-36
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    • 2014
  • The objective of this study is to estimate soil loss in the buffer zone of Guem river with future climate change simulation. Revised Universal Soil Loss Equation (RUSLE) model was used for the estimation of soil loss at the buffer zone of Guem river. As results of simulations, the area of the maximum soil loss potential was estimated as the Cheongsung-myeon Okchun-gun Chungcheongbuk-do. The soil losses were estimated to be 106.67 and 103.00 ton/ha/yr for the 2020 segi (2015-2025) and 2040 segi (2035-2045) in the Cheongsung-myeon area, respectively. Also, the estimated average values of soil losses in the Cheongsung-myeon with future climate change was 110.78 ton/ha/yr.