• Title/Summary/Keyword: soil flexibility

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Residual displacement estimation of simple structures considering soil structure interaction

  • Aydemir, Muberra Eser;Aydemir, Cem
    • Earthquakes and Structures
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    • v.16 no.1
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    • pp.69-82
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    • 2019
  • As the residual displacement and/or drift demands are commonly used for seismic assessment of buildings, the estimation of these values play a very critical role through earthquake design philosophy. The residual displacement estimation of fixed base structures has been the topic of numerous researches up to now, but the effect of soil flexibility is almost always omitted. In this study, residual displacement demands are investigated for SDOF systems with period range of 0.1-3.0 s for near-field and far-field ground motions for both fixed and interacting cases. The elastoplastic model is used to represent non-degrading structures. Based on time history analyses, a new simple yet effective equation is proposed for residual displacement demand of any system whether fixed base or interacting as a function of structural period, lateral strength ratio and spectral displacement.

3-Dimensional Static and Dynamic Analysis of Soil-Framework Interaction System (지반-골조구조물 상호작용계의 3차원 정.동적 해석)

  • 서상근;장병순
    • Computational Structural Engineering
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    • v.10 no.2
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    • pp.243-254
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    • 1997
  • When dynamic loads such as mechanical load, wind load, and seismic load, which causing a vibration, acts on the body of the 3-D framework resting on soil foundation, it is required to consider the dynamic behavior of soil-space framework interation system. Thus, this study presents the 3-dimensional soil-interaction system analyzed by finite element method using 4-node plate elements with flexibility, 2-node beam elements, and 8-node brick elements for the purpose of idealizing an actual structure into a geometric shape. The objective of this study is the formulation of the equation for a dynamic motion and the development of the finite element program which can analyze the dynamic behavior of soil-space framework interaction system.

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An experimental investigation on dispersion and geotechnical properties of dispersive clay soil stabilized with Metakaolin and Zeolite

  • Ahmadreza Soltanian;Amirali Zad;Maryam Yazdib;Amin Tohidic
    • Geomechanics and Engineering
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    • v.36 no.6
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    • pp.589-599
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    • 2024
  • Dispersion occurs when clay soil disperses under specific conditions and is rapidly washed away. While there are numerous methods for rectifying it, they are neither cost nor time-effective. The current study used metakaolin and zeolite to improve heavily dispersive clay soil either separately or in combination at 0%, 2%, 4%, 6%, and 8% of the soil weight. After 7 days of curing, the samples were tested to determine the extent of change in the dispersion potential, as well as the improvement of the geotechnical properties of the soil. The results indicated that the addition of 2% zeolite with 6% to 8% metakaolin decreased the dispersion potential considerably. Double hydrometry test findings revealed that the dispersion potential decreased by almost 70% and entered the non-dispersive group; the crumb test also revealed this. Atterberg limits testing indicated a decrease in the plasticity index which reduced the flexibility of the samples. The greatest decrease in PI (67.5%) was achieved with the addition of 8% zeolite plus 8% metakaolin to the soil. The results of density tests revealed that a decrease in the optimal moisture content increased the maximum dry density of soil. This increase in density was a response to the high reactivity of metakaolin with calcium hydroxide and the formation of calcium hydroxide hydrate gel. This eventually caused an increase in the unconfined compressive strength, the greatest increase in strength of about 1.8-fold was observed with a combination of 2% zeolite and 6% metakaolin compared to the unmodified sample.

A Simplified Soil-Structure Interaction Analytical Technique of Embedded Structure and Structure on Layered Soil Sites (매입구조물(埋入構造物)과 층상지반상(層狀地盤上) 구조물(構造物)에 대한 지반(地盤)-구조물(構造物) 상호(相互) 작용(作用)의 단순해석(單純解析))

  • Joe, Yang Hee;Lee, Yong Il;Kim, Jong Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.7 no.2
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    • pp.45-57
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    • 1987
  • The dynamic behavior of a structure by earthquake is considerably affected by the flexibility of the base soil. This phenomenon is called dynamic soil-structure interaction effect. There are two broad categories of soil-structure interaction analytical technique: direct method and substructure method. Substructure method, in contrast to direct method, has many limitations in applying to embedded structures or structures on layered soil sites, while it is relatively simple. In this paper, a simplified soil-structure interaction analytical procedure using substructure method is proposed to eliminate its original limitations. The proposed method is well applicable to embedded structures or structures on layered soil sites with as good results as FLUSH.

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Calculation model for the shear strength of unsaturated soil under nonlinear strength theory

  • Deng, Dongping;Wen, Shasha;Lu, Kuan;Li, Liang
    • Geomechanics and Engineering
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    • v.21 no.3
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    • pp.247-258
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    • 2020
  • The shear strength of unsaturated soils, a research hotspot in geotechnical engineering, has great guiding significance for geotechnical engineering design. Although kinds of calculation models for the shear strength of unsaturated soil have been put forward by predecessors, there is still need for new models to extensively consider the nonlinear variation of shear strength, particularly for the nonlinear effect of the net normal stress on the shear strength of unsaturated soil. Here, the shear strength of unsaturated soils is explored to study the nonlinear effects of net normal stress with the introduction of a general nonlinear Mohr-Coulomb (M-C) strength criterion, and the relationship between the matric suction (or suction stress) and degree of saturation (DOS) constructed by the soil-water characteristics curve (SWCC) of van Genuchten is also applied for unsaturated soil. Then, two calculation models (i.e., an envelope shell model and an effective stress model) are established for the shear strength of unsaturated soils under the nonlinear strength theory. In these two models, the curve of the shear strength of unsaturated soils versus the net normal stress exhibits a tendency to gently. Moreover, the proposed formulas have flexibility and convenience with five parameters (for the effective stress model) or six parameters (for the envelope shell model), which are from the M-C strength parameters of the saturated soil and fitting parameters of SWCC of van Genuchten. Thereafter, by comparison with the classical theory of the shear strength of unsaturated soils from some actual cases, the rationality and accuracy of the present models were verified.

High MSE wall design on weak foundations

  • Mahmoud Forghani;Ali Komak Panah;Salaheddin Hamidi
    • Geomechanics and Engineering
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    • v.36 no.4
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    • pp.329-341
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    • 2024
  • Retaining structures are one of the most important elements in the stabilization of excavations and slopes in various engineering projects. Mechanically stabilized earth (MSE) walls are widely used as retaining structures due to their flexibility, easy and economical construction. These benefits are especially prominent for projects built on soft and weak foundation soils, which have relatively low resistance and high compressibility. For high retaining walls on weak foundations, conventional design methods are not cost-effective. Therefore, two alternative solutions for different foundation weakness are proposed in this research: optimized multi-tiered MSE walls and single tier wall with foundation improvement. The cost optimization considers both the construction components and the land price. The results show that the optimal solution depends on several factors, including the foundation strength and more importantly, the land price. For low land price, the optimized multi-tiered wall is more economical, while for high land price (urban areas), the foundation improvement is preferable. As the foundation strength decreases, the foundation improvement becomes inevitable.

Seismic Behaviors of Concrete-Suction-Type Offshore Wind Turbine Supporting Structures Considering Soil-Structure Interaction (지반-구조물 상호작용을 고려한 콘크리트 석션식 해상풍력 지지구조물의 지진거동 특성)

  • Lee, Jin Ho;Jin, Byeong-Moo;Bae, Kyung-Tae
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.4
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    • pp.319-327
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    • 2017
  • In this study, characteristics of seismic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures are investigated. Applying hydrodynamic pressure from the surrounding sea water and interaction forces from the underlying soil to the structural system which is composed of RNA, the tower, and the supporting structure, a governing equation of the system is derived and its earthquake responses are obtained. It can be observed from the analysis results that the responses are significantly influenced by soil-structure interaction because dynamic responses for higher natural vibration modes are increased due to the flexibility of soil. Therefore, the soil-structure interaction must be taken into consideration for accurate assessment of dynamic behaviors of offshore wind turbine systems using concrete-suction-type supporting structures.

Evaluation of the Sequential Behavior of Tieback Wall in Sand by Small Scale Model Tests

  • Seo, Dong-Hee;Chang, Buhm-Soo;Jeong, Sang-Seom;Kim, Soo-Il
    • Journal of the Korean Geotechnical Society
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    • v.15 no.3
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    • pp.113-129
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    • 1999
  • In this study, a total of 12 types of sequential model tests were conducted at the laboratory for small scale anchored walls. The sequential behavior for flexible wall embedded in sand was investigated by varying degrees of relative density of Joomoonjin sand and flexibility number of model wall. The model tests were carried out in a 1000mm width, 1500mm length, and 1000mm high steel box. Load cells, pressure cells, displacement transducer and dial gauges were used to measure the anchor forces, lateral wall deflections, lateral earth pressures and vertical displacements of ground surface, respectively. Limited model tests were performed to examine the parameters for soil-wall interaction model and the formulation of analytical method was revised in order to predict the behavior of anchored wall in sand. Based on the model tests and proposed analytical method, model simulations were performed and the predictions by the present approach were compared with measurements by the model tests and predictions by other commercial programs. It is shown that the prediction by the present approach simulates qualitatively well the general trend observed for model test.

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Development of GRld-eased Soil MOsture Routing Model (GRISMORM) Applied to Bocheongchun Watershed (격자기반의 토양수분추적표형 개발 : 보청천 유역 사례연구)

  • 김성준;채효석
    • Spatial Information Research
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    • v.7 no.1
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    • pp.39-48
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    • 1999
  • A GRId-based Soil MOsture Routing Model(GRISMORM) which predicts temporal variation and spatial distribution of water balance on a daily time step for each grid element of the watershed was developed. The model was programmed by C-language which aims for high flexibility to any kind of GIS softwares. The model uses ASCII-formatted map data supported by the irregular gridded map of the GRASS(Geographic Resources Analysis Support System)-GIS and generates daily or monthly spatial distribution map of water balance components within the watershed. The model was applied to Ipyunggyo watershed(75.6$km^2$) ; the part of Bocheongchun watershed. Predicted streamflows resulting from two years(95 and 96) daily data were compared with those observed at the watershed outlet. The results of temporal variation and spatial distribution of soil moisture are also presented by using GRASS.

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Effects of Raft Flexibility on the Behavior of Piled Raft Foundations in Sandy Soil (사질토에 근입된 말뚝지지 전면기초의 기초판 연성률에 따른 거동 분석)

  • Song, Su-Min;Shin, Jong-Young;Jeong, Sang-Seom
    • Journal of the Korean Geotechnical Society
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    • v.39 no.3
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    • pp.5-16
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    • 2023
  • The effect of raft flexibility on piled raft foundations in sandy soil was investigated using a numerical analysis and an analytical study. The investigation's emphasis was the load sharing between piles and raft following the raft rigidity (KR), end-bearing conditions. The case of individual piles and subsequently the response of groups of piles was analyzed using a 3D FEM. This study shows that the αpr, load-sharing ratio of piled raft foundations, decreases as the vertical loading increases and as the KR decreases. This tendency is more obvious when using friction piles compared to using end-bearing piles. The effect of raft rigidity is found to be more significant for the axial force distribution - each pile within the foundations has almost similar axial forces of the pile head with a flexible raft; however, each pile has different values with rigid rafts, especially with the end-bearing piles. The axial force of the pile base with floating piles shows similar point-bearing resistance for all the piles; however, it shows different values with end-bearing piles. The differential settlement ratio of rafts showed a larger value with lower KR.