• Geomechanics and Engineering
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• 제37권3호
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• pp.253-262
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• 2024

Dynamic properties are pivotal in soil analysis, yet their experimental determination is hampered by complex methodologies and the need for costly equipment. This study aims to predict dynamic soil properties using static properties that are relatively easier to obtain, employing machine learning techniques. The static properties considered include soil cohesion, friction angle, water content, specific gravity, and compressional strength. In contrast, the dynamic properties of interest are the velocities of compressional and shear waves. Data for this study are sourced from 26 boreholes, as detailed in a geotechnical investigation report database, comprising a total of 130 data points. An importance analysis, grounded in the random forest algorithm, is conducted to evaluate the significance of each dynamic property. This analysis informs the prediction of dynamic properties, prioritizing those static properties identified as most influential. The efficacy of these predictions is quantified using the coefficient of determination, which indicated exceptionally high reliability, with values reaching 0.99 in both training and testing phases when all input properties are considered. The conventional method is used for predicting dynamic properties through Standard Penetration Test (SPT) and compared the outcomes with this technique. The error ratio has decreased by approximately 0.95, thereby validating its reliability. This research marks a significant advancement in the indirect estimation of the relationship between static and dynamic soil properties through the application of machine learning techniques.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1214-1221
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• 2011

It is an well-known fact that dynamic properties should be considered in design and maintenance of civil structures undergoing dynamic force such as rail track. For designing of the rail tack structures, dynamic properties of track bed soil such as shear modulus (G) and damping coefficients(D) obtained in small to medium range of shear strain must be known. In general, small size sample of D=5 cm and H=10cm has been used mostly for test convenience. However, ratio of largest particle diameter of the soil to sample diameter is very important and affects to the values of dynamic soil properties in track bed. In this study, an RC/TS test apparatus was built and was run for testing a medium size soil sample that can handle with compacted soil sample up to 10 cm diameter and 20 cm height.

• 대한토목학회논문집
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• 제10권2호
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• pp.103-112
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• 1990

본 연구는 내진설계시 많은 불확실성을 내포하는 지반의 거동특성을 규명하고, 적용대상지반의 확충 및 경제성 제고를 위하여 토사지반의 동적지반특성 평가 및 지반-구조물 거동 특성을 고찰하였다. 예제해석은 토사지반에 원전 containment 구조물이 설치된 경우를 가상하여 지진하중에 대한 지반-구조물 시스템의 거동을 반무한체해석과 유한요소해석으로 분석하였다. 이는 토사지반에 원전이 건설될 경우에 고려해야 할 안정성 및 경제성 분석의 일환으로 수행되었으며, 토사지반의 큰 비선형거동을 정확하게 해석에 반영하기 위한 해석 software와 지반입력 data의 합리적인 평가방안 등을 예제해석을 통하여 분석하였다. 예제해석결과를 종합해 볼 때 토사지반의 동적거동의 정확한 분석을 위하여 비선형 유한요소해석은 Seed & Idriss 모델이, 선형 유한요소해석은 지진하중에 대한 1차원 지반거동시 변형율에서의 동적지반특성을 이용한 방법이, 반무한체해석은 정적하중시 변형율에서의 동적지반특성을 이용한 방법이 가장 합리적으로 동적지반특성을 평가하는 것으로 추천할 수 있다.

• Geomechanics and Engineering
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• 제16권5호
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• pp.547-558
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• 2018

Studies of soil dynamic properties in Malaysia are still very limited. This study aims to investigate the dynamic properties of two selected tropical residual soils (i.e., Sandy Clay and Sandy Silt) and a sand mining trail (Silty Sand) in Peninsular Malaysia using 1g shaking table test. The use of 1g shaking table test for soil dynamic testing is often constrained to large strain level and small confining pressure only. Three new experimental setups, namely large laminar shear box test (LLSBT), small chamber test with positive air pressure (SCT), and small sample test with suction (SSTS) are attempted with the aims of these experimental setups are capable of evaluating the dynamic properties of soils covering a wider range of shear strain and confining pressure. The details of each experimental setup are described explicitly in this paper. Experimental results show that the combined use of the LLSBT and SCT is capable of rendering soil dynamic properties covering a strain range of 0.017%-1.48% under confining pressures of 5-100 kPa. The studied tropical residual soils in Malaysia behaved neither as pure sand nor clay, but show a relatively good agreement with the dynamic properties of residual soils in Singapore. Effects of confining pressure and plasticity index on the studied tropical residual soils are found to be insignificant in this particular study.

• Structural Engineering and Mechanics
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• 제10권4호
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• pp.299-312
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• 2000

The response of an embedded body to dynamic loads is greatly influenced by the reactions of the soil to the motion of the body. The properties of the soil surrounding embedded bodies (e.g., piles) may be different than those of the far-field for a variety of reasons. It may be weakened or strengthened according to the method of installation of piles, or altered due to applying one of the soil strengthening technique (e.g., electrokinetic treatment of soil, El Naggar et al. 1998). In all these cases, the shear strength of the soils and its shear modulus vary gradually in the radial direction, resulting in a radially inhomogeneous soil layer. This paper describes an analysis to compute vertical and torsional dynamic soil reactions of a radially inhomogeneous soil layer with a circular hole. These soil reactions could then be used to model the soil resistance in the analysis of the pile vibration under dynamic loads. The soil layer is considered to have a piecewise, radial variation for the complex shear modulus. The model is developed for soil layers improved using the electrokinetic technique but can be used for other situations where the soil properties vary gradually in the radial direction (strengthened or weakened). The soil reactions (impedance functions) are evaluated over a wide range of parameters and compared with those obtained from other solutions. A parametric study was performed to examine the effect of different soil improvement parameters on vertical and torsional impedance functions of the soil. The effect of the increase in the shear modulus and the width of the improved zone is investigated.

• Geomechanics and Engineering
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• 제24권2호
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• pp.105-113
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• 2021

Deformations in soils induced by dynamic loads cause damage to the structures above the soil layers. It is important for geotechnical engineering practice that how the soil behaves due to repeated loads and the necessary precautions to be taken accordingly. Turkey is one of the most important seismic regions in Europe and earthquake studies to be conducted in this area are intended to reduce the damage as a result of taking the necessary measures. To determine the properties of soils under dynamic loads, stress-controlled dynamic triaxial and resonant column tests can be performed. In this study, these experiments were implemented in the laboratory on the clayey sand soil samples obtained from Bilecik Söğüt. To evaluate the effects of the confining pressure and rate of loading on the dynamic behavior of soils, samples were dynamically loaded by different rates at varying confining pressures. As a result, the changes in stress-strain properties of soils under dynamic loads were investigated. The alteration in behavior in terms of modulus reduction and damping ratios was obtained to vary a lot with the change of the lateral pressure on soil along with the frequency of the load.

• Geomechanics and Engineering
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• 제12권5호
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• pp.815-830
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• 2017

Due to numerous environmental concerns in recent years, the search for and the development of sustainable technologies have been pursued. In particular, environmentally friendly methods of soil improvement, such as the potential use of biopolymers, have been researched. Previous studies on the use of biopolymers in soil improvement have shown that they can provide substantial strengthening efficiencies. However, in order to fully understand the applicability of biopolymer treated soils, various properties of these soils such as their dynamic properties must be considered. In this study, the dynamic properties of gel-type biopolymer treated soils were observed through the use of resonant column tests. Gellan gum and Xanthan gums were the target gel-type biopolymers used in this study, and the target soil for this study was jumunjin sand, the standard sand of Korea. Through this study it was demonstrated that biopolymers can be used to enhance the dynamic properties of the soil, and that they offer possibilities of reuse to reduce earthquake related soil failures.

• 한국지반공학회지:지반
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• 제6권2호
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• pp.5-20
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• 1990

지반-구조물의 동적 상호작용 해석에 있어서, 흙의 특성치들 뿐만 아니라 입력지진 자체도 무척 Random하다. 본 논문에서는 이 Randomness를 고려하기 위하여 확률론적 방법을 적용하여 상호작용 해석에 미치는 영향을 연구하였다. 이 확률론적 적용을 위해 Elastic Half Space 이론에 의해 얻어진 Complex Response 방법, Random Vibration Theory와 Rosenblueth의 Two Point Estimate 방법을 사용하여 해석을 수행하여 다음과 같은 결론을 얻었다. 1) 흙의 동적 특성치 뿐만 아니라 Kanai-Tajimi에 의하여 제안된 입력지진의 PSD Function 의 불확정성도 상당히 큼을 알 수 있었다. 이때의 Parameter의 변동계수는 0.4에서 0.6의 범위를 갖는다. 2) 흙의 동적 특성치의 불확정성의 영향이 입력지진의 그것보다는 구조물에 미치는 영향이 큼 을 알 수 있었다. 3) 입력지진과 흙의 동적 특성치 사이의 상관계수에 의한 영향은 무척 작음을 알 수 있었다.

• Geomechanics and Engineering
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• 제36권4호
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• pp.391-406
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• 2024

In order to study the soil seasonal dynamic characteristics in the regions with four distinct seasons, the soil dynamic triaxial experiments were conducted by considering the environmental temperature range from -30℃ to 30℃. The results demonstrate that the dynamic soil properties in four seasons can change greatly. Firstly, the dynamic triaxial experiments were performed to obtain the dynamic stress-strain curve, elastic modulus, and damping ratio of soil, under different confining pressures and temperatures. Then, the experiments also obtain the dynamic cohesion and internal friction angle of the clay under the initial strain, and the changing rule was summarized. Finally, the results show that the dynamic elastic modulus and dynamic cohesion will increase significantly when the clay is frozen; as the temperature continues to decrease, this increasing trend will gradually slow down, and the dynamic damping ratio will go down when the freezing temperature decreases. In this paper, the change mechanism is objectively analyzed, which verifies the reliability of the conclusions obtained from the experiment.

• 대한토목학회논문집
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• 제10권2호
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• pp.91-102
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• 1990

본 연구는 다양한 지반조건에 따른 동적거동해석의 안정성 및 경제성을 분석하기 위하여 토사지반을 포함하는 시험부지를 선택하여 토사지반에서는 미소변형율의 crosshole test 및 downhole test와 대변형율의 반복삼축시험, 암반에서는 미소변형율에서 현장시험인 crosshole test, downhole test와 실내시험인 sonic test를 실시해 변형율에 따른 지반의 동적전단계수, 감쇠비와 포아슨비 등을 측정하였다. 시험으로 구한 동적지반특성과 기초특성과의 상관관계를 회귀분석을 통하여 분석하였고, 지반의 설계대표치는 시험결과를 토대로 지반별 분포특성 및 영향요인을 고려하여 토사지반에서는 비선형 응력-변형모델로, 암반에서는 미소변형율에서의 동적지반특성을 산정하였다. 상기의 지반구성방정식과 대표치 산정과정은 실제 시험결과 분석, 지반입력 data 산정에 활용 가능하도록 체계화하였다.