• Geomechanics and Engineering
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• 제9권1호
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• pp.101-113
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• 2015

Saturated soil hydraulic conductivity is a very important soil parameter in numerous practical engineering applications, especially rainfall infiltration and slope stability problems. This parameter is difficult to measure since it is very highly sensitive to various soil conditions. There have been many analytical and empirical formulas to predict saturated soil hydraulic conductivity based on experimental data. However, there have been few studies to investigate in-situ hydraulic conductivity of weathered granite soils, which constitute the majority of soil slopes in Korea. This paper introduces an estimation method to derive saturated hydraulic conductivity of Korean weathered granite soils using in-situ experimental data which were obtained from a variety of slope areas of South Korea. A robust regression analysis was performed using different physical soil properties and an empirical solution with an $R^2$ value of 0.9193 was suggested. Besides that this research validated the proposed model by conducting in-situ saturated soil hydraulic conductivity tests in two slope areas.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.1117-1121
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• 2010

Several isotropic compression-expansion tests and a series of drained conventional traxial tests with various confining pressures for relative density of Beakma river sand 25%, 50%, 80% and 100% selecting Lade's Single Work-Hardening constitutive model. This examination materials use regression analysis as a basis, depending on the relative density of soil parameters change statement attributes. Yield fuction represent the soil parameters h and $\alpha$ is not affected by the changes in the relative density. $\eta_1$ could be replaced by fomula. And Numerical analysis results predicted very good and could confirm that.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.31-36
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• 2010

This paper introduces a practical determination method for soil parameters adopted in the new performance based design code for port and harbour facilities in Japan. In the new port-design code, the depth profile of the derived values is modeled as the profile of the estimated values so as to be either the mean value or the regression line, then the correction factors are multiplied to the estimated value according to the coefficient of variation (if COV > 0.1) and the number of the data entries (if n < 10). The new port-design code is applied to the unconfined compression test results for the Hiroshima Port clay in order to evaluate the undrained shear strengths. From the discussion, it is emphasized that not only the statistic treatment but also the engineering judgment are required in the procedure of the soil parameter determination for the reliability design.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.596-601
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• 2000

The paper presents free vibration and stability analyses of a non-uniform Timoshenko beam resting on a two-parameter elastic soil. The soil parameters can vary along the spat and is assumed to be two-parameter model including the effects of both transverse shear deformation and elastic foundation Governing equations related to the vibration and the stability of the beam are derived from Hamilton's principle, and the resulting eigen-value problems can be solved to give natural frequencies and critical force by finite element method. Numerical results for both vibration and stability of beams under an axial force are presented and compared with other available solutions. Finally, vibration frequencies, mode shapes and critical forces are investigated for various thickness ratios, shear foundation parameter, Winkler foundation parameter and boundary conditions of tapered Timoshenko beams.

• 한국조경학회지
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• 제29권1호
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• pp.161-167
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• 2001

The purpose of this study is to find out the difference of Zoysia matrella's evaporation in between 100 percent soil and mixed soil with 50 percent of perlite to create green spaces on the artificial ground. It is believed that the weight against the artificial ground will be reduced, provided the vegetation is possible in the circumstance of the mixed sol with 50 percent of perlite. The study employed a modified Makkink's model by Iwasa who had developed the model for estimating Zoysia matrella's evaporation in the natural ground using the Makkink's formula in 1997 at Chiba University, Japan. The parameter of Makkink's formula is the solar radiation. For that reason, the Makkink's formula is simple and easy to measure the parameter and has a high utility. If the outcomes from mixed soil are close to modified Makkinks formula, the modified Makkink's formula will be applied to estimate in the artificial ground with mixed soil with 50 percent of perlite. Weather observation and actual amount of evaporation of Zoysia matrella have been measured, and the relation between weather condition and actual amount of evaporation had been also investigated. In line with this, we found out that there is a relevant relationship between daily average temperature, the modified Makkink's model by Iwasa, and the actual amount of evaporation. As the results of the experiment, the outcomes from mixed soil with 50 percent of perlite have very high relation to 100 percent soil. In addition, mixed soil has more adhesion with water than natural soil. However, it needs to be adequately maintained in terms of fertilization and damage from disease and harmful insects until the gras fastens its roots into the soil. By using mixed soil with 50 percent of perlite, the load from soil on the artificial ground can be reduced. The study on the growth of the grass throughout the plant vegetation and the actual amount of evaporation in the mixed soil with 50 percent of perlite should be performed in the future.

• 한국농림기상학회지
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• 제10권2호
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• pp.35-46
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• 2008

토양수분은 사면에서의 수문학적 과정의 가장 중요한 요소이며, 불포화대에서의 흐름을 결정하는 중요요소이다. 본 연구는 전이함수모형을 이용하여 토양수분의 시간적 공간적 분포 양상을 인지하고자 한다. 이를 위하여, 광릉 수목원 슈퍼사이트 원두부 소유역 내에서 TDR을 이용하여 2시간 간격으로 연속 측정한 10cm 깊이의 토양수분 결과를 전이함수를 통하여 분석하였다. 강우 자료를 입력변수로, 지표면으로부터 10cm 깊이의 실측 토양수분 자료를 출력변수로 선정하여 단일 입출력 전이함수를 전개하였다. 토양수분의 계절적인 변화를 분석하기 위해 5월과 9월의 전이함수를 비교하였다. 시계열 전이 함수는 크게 자료의 전처리, 모형구조의 규명, 후보 모형군의 구성, 모수추정, 모형진단 등의 과정을 통해서 전개되며 10cm 깊이의 토양수분과 강우의 상관관계를 보여준다. 도출한 전이함수 시계열 모형에서 10cm 깊이의 토양수분은 강우에 의한 영향이 지배적이었으며, 지점별 경사에 따라 토양수분의 변동성이 크게 차이를 나타내지 않았다. 이는 10cm 깊이의 토양수분 변동량은 각 지점의 경사보다 강우에 의한 반응이 우세하다는 것을 시사한다. 계절별로 상이한 모의 결과는 식생의 활동이 활발한 5월에는 식생이 토양수분 이동에 많은 영향을 미치며 식생이 토양수분을 해석하는데 중요한 변수로 작용함을 나타낸다. 본 연구 결과는 광릉 산림과 같은 복잡 경관에서 토양수분의 분포를 이해하는 기반자료가 될 것으로 기대된다.

• Geomechanics and Engineering
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• 제16권6호
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• pp.577-588
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• 2018

A major concern in deep excavation project in soft clay deposits is the potential for adjacent buildings to be damaged as a result of the associated excessive ground movements. In order to accurately determine the wall deflections using a numerical procedure such as the finite element method, it is critical to use the correct soil parameters such as the stiffness/strength properties. This can be carried out by performing an inverse analysis using the measured wall deflections. This paper firstly presents the results of extensive plane strain finite element analyses of braced diaphragm walls to examine the influence of various parameters such as the excavation geometry, soil properties and wall stiffness on the wall deflections. Based on these results, a multivariate adaptive regression splines (MARS) model was developed for inverse parameter identification of the soil relative stiffness ratio. A second MARS model was also developed for inverse parameter estimation of the wall system stiffness, to enable designers to determine the appropriate wall size during the preliminary design phase. Soil relative stiffness ratios and system stiffness values derived via these two different MARS models were found to compare favourably with a number of field and published records.

• Journal of Advanced Research in Ocean Engineering
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• 제2권2호
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• pp.86-98
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• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• 대한토목학회논문집
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• 제9권3호
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• pp.115-123
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• 1989

본(本) 논문(論文)은 과거(過去) 13년간(年間)(1974~1986) 주택공사(住宅公社)가 전국(全國) 74개(個) 도시(都市), 176개(個) 주택단지(住宅團地)에서 실시(實施)한 제반토질시험결과(諸般土質試驗結果)를 통일분류법(統一分類法)에 의(依)한 흙의 종류별(種類別), 토질정수(土質定數)의 분산(分散)의 정도(程度)를 확률적(確率的)으로 분석(分析)한 것이다. 이 논문(論文)에서 분석(分析)한 토질정수(土質定數)는 자연함수비(自然含水比), 토립자(土粒子)의 비중(比重), 아터버그 한계(限界), 표준매입시험치(標準買入試驗値), 일축압축강도(一軸壓縮强度), 압축지수(壓縮指數) 그리고 강도정수(强度定數) 등(等)이다. 연구분석(硏究分析)한 결과(結果), 물리적(物理的) 저성질(藷性質)은 통계변수(統計變數)인 변동계수(變動係數)를 기준으로 하여 비교(比較)할때 변동(變動)의 범위(範圍)가 비교적(比較的) 적은 반면(反面)에, 강도정수(强度定數)는 40%, 압축지수(壓縮指數)는 32% 정도(程度)의 변동계수(變動係數)를 가지며, 비중(比重)은 사질도(砂質土)에서 0.87-2.49%, 점성토(粘性土)에서 0.91-5.03%로 분산(分散)의 정도(程度)가 매우 작음을 확인(確認)하였다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.267-274
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• 1999

Since the seismic response of dams can be strongly influenced by the dam-reservior interaction in needs to be taken into account in the seismic design of dams. In general a substructure method is employed to solve the dam-reservoir interaction problem in which the dam body is modeled with finite elements and the infinite region of a reservoir using a transmitting boundary. When the water is modeled as a compressible fluid the equation is formulated in frequency domain. But nonlinear behavior of dam body cannot be studied easily in the frequency domain method. In this study time domain formulation of the dam-reservoir-soil interaction is proposed based onthe lumped parameter modeling of the reservoir region, The frequency dependent dynamic-stiffness coefficients of the reservoir are converted into frequency independent lumped-parameters such as masses dampers and springs. The soil-structure interactionis modeled using lumped parameters in similar way. the ground is assumed as a visco-elastic stratum on the rigid bedrock. The dynamic stiffnesses of the rigid surface foundation are calculated using the hyperelement method and are converted into lumped parameters. The application example demonstrated that the lumped parameter model gives almost identical results with the frequency domain formulation.