• Title/Summary/Keyword: Soil parameter

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Design-Parameter Computation of Subsurface Investigation Profile on Probability Method (확률론적 방법에 의한 지반조사 자료의 설계정수 산정)

  • 신은철;김종인;이준철
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.833-840
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    • 2003
  • The stability of structure, effectiveness of design and construction are very important factors in soil-structure design. The design-parameter is based on the test through laboratory-test and field-test. There are two ways to obtain the design-parameter. One is to through test, and the other is through relative documents and references. Recently, statistics has been used to get reliable data. In this study, Kriging method as Geostatistics and the theory of Bayesian's inference are used and the design-parameters are obtained. As the result of this study to the design-parameter is reliable and information about soil condition and soil properties in design and construction is easily found.

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The Simulation of Pore Size Distribution from Unsaturated Hydraulic Conductivity Data Using the Hydraulic Functions (토양 수리학적 함수를 이용한 불포화 수리전도도로부터 공극크기분포의 모사)

  • Yoon, Young-Man;Kim, Jeong-Gyu;Shin, Kook-Sik
    • Korean Journal of Soil Science and Fertilizer
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    • v.43 no.4
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    • pp.407-414
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    • 2010
  • Until now, the pore size distribution, PSD, of soil profile has been calculated from soil moisture characteristic data by water release method or mercury porosimetry using the capillary rise equation. But the current methods are often difficult to use and time consuming. Thus, in this work, theoretical framework for an easy and fast technique was suggested to estimate the PSD from unsaturated hydraulic conductivity data in an undisturbed field soil profile. In this study, unsaturated hydraulic conductivity data were collected and simulated by the variation of soil parameters in the given boundary conditions (Brooks and Corey soil parameters, ${\alpha}_{BC}=1-5L^{-1}$, b = 1 - 10; van Genuchten soil parameters, ${\alpha}_{VG}=0.001-1.0L^{-1}$, m = 0.1 - 0.9). Then, $K_s$ (1.0 cm $h^{-1})$ was used as the fixed input parameter for the simulation of each models. The PSDs were estimated from the collected K(h) data by model simulation. In the simulation of Brooks-Corey parameter, the saturated hydraulic conductivity, $K_s$, played a role of scaling factor for unsaturated hydraulic conductivity, K(h) Changes of parameter b explained the shape of PSD curve of soil intimately, and a ${\alpha}_{BC}$ affected on the sensitivity of PSD curve. In the case of van Genuchten model, $K_s$ and ${\alpha}_{VG}$ played the role of scaling factor for a vertical axis and a horizontal axis, respectively. Parameter m described the shape of PSD curve and K(h) systematically. This study suggests that the new theoretical technique can be applied to the in situ prediction of PSD in undisturbed field soil.

지표수 수위변동을 이용한 대수층 수리상수 추정

  • 하규철;조민조
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2004.09a
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    • pp.426-430
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    • 2004
  • In aquifers connected hydraulically, the levels of groundwater respond to stream stages. Analytical solutions by Laplace transform and convolution integral are used to get some response patterns about hydrogeoiogic parameter such as hydraulic conductivity, specific storage in confined aquifer. This method has the advantage to do hydrogeologic parameter estimations only with stream stage changes.

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The Influence of Fitting Parameters on the Soil-Water Characteristics Curve in Stability Analysis of an Unsaturated Natural Slope (불포화 자연사면의 안정해석시 흙-함수특성곡선 맞춤계수의 영향)

  • Kim, Jae-Hong;Yoo, Yong-Jae;Song, Young-Suk
    • The Journal of Engineering Geology
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    • v.31 no.2
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    • pp.165-178
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    • 2021
  • The influence of Soil-Water Characteristic Curve (SWCC) fitting parameters for an unsaturated natural slope was evaluated through seepage and slope stability analysis as a function of rainfall. Soil samples were collected from the study area in Jirisan National Park and the physical and mechanical characteristics of unsaturated soil layers were measured in laboratory tests. The saturation depth was calculated via seepage analysis by changing fitting parameters α, the parameter related to the Air Entry Value (AEV) and n, the parameter related to the slope of the SWCC in the range of natural conditions. Slope stability analysis using the limit equilibrium method considered the calculated depth of saturation. Results from seepage analysis for various rainfall conditions indicate the saturation depth in the soil layer suddenly increased as the fitting parameter α decreased; the saturation time for the entire soil layer also decreased. Slope stability analysis considering the calculated depth of saturation shows that the slope safety factor rapidly decreased as the fitting parameter α decreased, whereas the variation in slope safety factor was very small when n increased. Hence, fitting parameter α has a large effect on saturation depth during rainfall and therefore on slope stability, whereas slope stability is relatively unaffected by the fitting parameter n.

Numerical studies on the effects of the lateral boundary on soil-structure interaction in homogeneous soil foundations

  • Li, Z.N.;Li, Q.S.;Lou, M.L.
    • Structural Engineering and Mechanics
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    • v.20 no.4
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    • pp.421-434
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    • 2005
  • In this paper, the finite element method is applied to investigate the effect of the lateral boundary in homogenous soil on the seismic response of a superstructure. Some influencing factors are presented and discussed, and several parameters are identified to be important for conducting soil-structure interaction experiments on shaking tables. Numerical results show that the cross-section width L, thickness H, wave propagation velocity and lateral boundaries of soil layer have certain influences on the computational accuracy. The dimensionless parameter L/H is the most significant one among the influencing factors. In other words, a greater depth of soil layer near the foundation should be considered in shaking table tests as the thickness of the soil layer increases, which can be regarded as a linear relationship approximately. It is also found that the wave propagation velocity in soil layer affects the numerical accuracy and it is suggested to consider a greater depth of the soil layer as the wave propagation velocity increases. A numerical study on a soil-structure experimental model with a rubber ring surrounding the soil on a shaking table is also conducted. It is found the rubber ring has great effect on the soil-structure interaction experiments on shaking table. The experimental precision can be improved by reasonably choosing the elastic parameter and width of the rubber ring.

Prediction of the Volumetric Water Content Using the Soil-Water Characteristic Curve on an Unsaturated Soil (흙-수분 특성곡선 방정식을 이용한 체적함수비의 예측)

  • Song, Chang-Seob
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.7 no.6
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    • pp.39-48
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    • 2004
  • The purpose of this paper was to confirm the application of the equation of the soil-water characteristic curve on an unsaturated soil. To this ends, a series of suction test was conducted on the selected 4 kinds of soil which is located in Korea, using the modified pressure extractor apparatus. And it was carried out to analyze the experimental parameters which can describe the soil-water characteristics, were determined by using the data obtained from the experiment. From the results, it was found that the matric suction was varied according to the grain size distribution, amount of fine grain particle and void ratio. Also it was found that the residual volumetric water content was decreased with the void ratio, but the index related air entry value, the soil parameter related water content and the parameter with residual water content were increased with the void ratio. And the application of equation of the soil-water characteristic curve was confirmed for the various conditions and the various state by the comparison between the volumetric water content measured by the experiment and the predicted values.

Estimation of Strength Parameter of Soil-NSS Mixture by Triaxial Compression Test (삼축압축시험을 이용한 NSS 혼합토의 강도정수 평가)

  • Oh, Sewook;Lee, Gilho;Kwon, Hyekkee;Kwon, Youngcheul
    • Journal of the Korean GEO-environmental Society
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    • v.14 no.11
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    • pp.65-71
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    • 2013
  • Despite of the various merits of soil pavement, it has not been widely adapted because portland cement was conventionally used as soil stabilizer to improve the mechanical properties such strength parameters. Recently, natural soil stabilizer(NSS) were developed and virtually adopted to several case of soil pavement construction under control of heavy metal pollution compared to cement-used cases. However, the application of natural soil stabilizer is not settled yet, and empirical design have been widely adopted. In this study, therefore, the strength parameter of soil-NSS mixture was estimated by some triaxial compression tests, CU-test. From the tests, the relationship between curing period and strength parameter such as internal friction and effective cohesion was examined. As a result, effective cohesion of dredged clay and granite soil increased as curing time is increased. However, internal friction is almost same result in all soil type used in this study.

Post-buckling analysis of piles by perturbation method

  • Zhao, M.H.;He, W.;Li, Q.S.
    • Structural Engineering and Mechanics
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    • v.35 no.2
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    • pp.191-203
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    • 2010
  • To investigate the critical buckling load and post-buckling behavior of an axially loaded pile entirely embedded in soil, the non-linear large deflection differential equation for a pinned pile, based on the Winkler-model and the discretionary distribution function of the foundation coefficient along pile shaft, was established by energy method. Assuming that the deflection function was a power series of some perturbation parameter according to the boundary condition and load in the pile, the non-linear large deflection differential equation was transformed to a series of linear differential equations by using perturbation approach. By taking the perturbation parameter at middle deflection, the higher-order asymptotic solution of load-deflection was then found. Effect of ratios of soil depth to pile length, and ratios of pile stiffness to soil stiffness on the critical buckling load and performance of piles (entirely embedded and partially embedded) after flexural buckling were analyzed. Results show that the buckling load capacity increases as the ratios of pile stiffness to soil stiffness increasing. The pile performance will be more stable when ratios of soil depth to pile length, and soil stiffness to pile stiffness decrease.

Utilizing the GOA-RF hybrid model, predicting the CPT-based pile set-up parameters

  • Zhao, Zhilong;Chen, Simin;Zhang, Dengke;Peng, Bin;Li, Xuyang;Zheng, Qian
    • Geomechanics and Engineering
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    • v.31 no.1
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    • pp.113-127
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    • 2022
  • The undrained shear strength of soil is considered one of the engineering parameters of utmost significance in geotechnical design methods. In-situ experiments like cone penetration tests (CPT) have been used in the last several years to estimate the undrained shear strength depending on the characteristics of the soil. Nevertheless, the majority of these techniques rely on correlation presumptions, which may lead to uneven accuracy. This research's general aim is to extend a new united soft computing model, which is a combination of random forest (RF) with grasshopper optimization algorithm (GOA) to the pile set-up parameters' better approximation from CPT, based on two different types of data as inputs. Data type 1 contains pile parameters, and data type 2 consists of soil properties. The contribution of this article is that hybrid GOA - RF for the first time, was suggested to forecast the pile set-up parameter from CPT. In order to do this, CPT data and related bore log data were gathered from 70 various locations across Louisiana. With an R2 greater than 0.9098, which denotes the permissible relationship between measured and anticipated values, the results demonstrated that both models perform well in forecasting the set-up parameter. It is comprehensible that, in the training and testing step, the model with data type 2 has finer capability than the model using data type 1, with R2 and RMSE are 0.9272 and 0.0305 for the training step and 0.9182 and 0.0415 for the testing step. All in all, the models' results depict that the A parameter could be forecasted with adequate precision from the CPT data with the usage of hybrid GOA - RF models. However, the RF model with soil features as input parameters results in a finer commentary of pile set-up parameters.

Threshold Subsoil Bulk Density for Optimal Soil Physical Quality in Upland: Inferred Through Parameter Interactions and Crop Growth Inhibition

  • Cho, Hee-Rae;Han, Kyung-Hwa;Zhang, Yong-Seon;Jung, Kang-Ho;Sonn, Yeon-Kyu;Kim, Myeong-Sook;Choi, Seyeong
    • Korean Journal of Soil Science and Fertilizer
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    • v.49 no.5
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    • pp.548-554
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    • 2016
  • Optimal range of soil physical quality to enhance crop productivity or to improve environmental health is still in dispute for the upland soil. We hypothesized that the optimal range might be established by comparing soil physical parameters and their interactions inhibiting crop growth. The parameter identifying optimal range covered favorable conditions of aeration, permeability and root extension. To establish soil physical standard two experiments were conducted as follows; 1) investigating interactions of bulk density and aeration porosity in the laboratory test and 2) determining effects of soil compaction and deep & conventional tillage on physical properties and crop growth in the field test. The crops were Perilla frutescens, Zea mays L., Solanum tuberosum L. and Secale cereael. The saturated hydraulic conductivity, bulk density from the root depth, root growth and stem length were obtained. Higher bulk density showed lower aeration porosity and hydraulic conductivity, and finer texture had lower threshold bulk density at 10% aeration bulk density. Reduced crop growth by subsoil compaction was higher in silt clay loam compared to other textures. Loam soil had better physical improvement in deep rotary tillage plot. Combined with results of the present studies, the soil physical quality was possibly assessed by bulk density index. Threshold subsoil bulk density as the upper value were $1.55Mg\;m^{-3}$ in sandy loam, $1.50Mg\;m^{-3}$ in loam and $1.45Mg\;m^{-3}$ in silty clay loam for optimal soil physical quality in upland.