• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.2
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• pp.35-46
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• 2008

Soil moisture is one of the important components in hydrological processes and also controls the subsurface flow mechanism at a hillslope scale. In this study, time series of soil moisture were measured at a hillslope located in Gwangneung National Arboretum, Korea using a multiplex Time Domain Reflectometry(TDR) system measuring soil moisture with bi-hour interval. The Box-Jenkins transfer function and noise model was used to estimate spatial distributions of soil moisture histories between May and September, 2007. Rainfall was used as an input parameter and soil moisture at 10 cm depth was used as an output parameter in the model. The modeling process consisted of a series of procedures(e.g., data pretreatment, model identification, parameter estimation, and diagnostic checking of selected models), and the relationship between soil moisture and rainfall was assessed. The results indicated that the patterns of soil moisture at different locations and slopes along the hillslope were similar with those of rainfall during the measurment period. However, the spatial distribution of soil moisture was not associated with the slope of the monitored location. This implies that the variability of the soil moisture was determined more by rainfall than by the slope of the site. Due to the influence of vegetation activity on soil moisture flow in spring, the soil moisture prediction in spring showed higher variability and complexity than that in early autumn did. This indicates that vegetation activity is an important factor explaining the patterns of soil moisture for an upland forested hillslope.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.4
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• pp.222-229
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• 2005

A simplified one-dimensional model STELLA was used to predict soil water movement in lllinois corn fields using soil water balance sheets. It offered the potential to increase understanding of soil nitrate and agrochemical leaching process. The model accounted for aU possible annual inputs and outputs of water from a closed ecosystem as represented by corn fields. Water inputs included precipitation, while outputs included runoff, transpiration, evaporation and drainage. To run the model required daily inputs of two climatic data measurements such as daily precipitation and pan evaporation. Vertical water flow through the soil profile was calculated with first order equation including the difference in hydraulic conductivity and matric potential at the various soil types. The output results included daily changes of water content in the soil layers and daily amount of water losses including run-off, percolation, transpiration. This model was verified using Illinois corn field data for the soil water content measured by neutron scattering methods through 1992 to 1994 growing seasons. Approximately 22 to 78% of simulated water contents agreed with the measured values and their standard deviation, depending on soil types, whereas 30 to 70% of simulated water values agreed with the measured values and their standard deviations depending on soil layers.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.37 no.6
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• pp.555-562
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• 2019

This paper presents soil deformation measurement in model chamber based on photogrammetry. We created an aluminum framed acrylic model chamber with soil inside and applied photogrammetry to measure soil deformation caused by loading tests. The soil consists of 40% black and 60% regular sand to create image contrast in soil images. In preprocessing, the self camera calibration was carried out for IOPs (Interior Orientation Parameters), followed by the space resection to estimate EOPs (Exterior Orientation Parameters) using control points located along the aluminum frame. Image matching was applied to measure the soil displacement. We tested different matching window sizes and the effect of image smoothing. Experimental results showed that 65x65 pixels of window size produced better soil deformation map and the image smoothing was useful to suppress the matching outliers. In conclusion, photogrammetry was able to efficiently generated soil deformation map.

• Structural Engineering and Mechanics
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• v.58 no.6
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• pp.1045-1075
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• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.

• Journal of Korean Society of Forest Science
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• v.94 no.4 s.161
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• pp.281-286
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• 2005

Trees enhance slope stability against down slope mass movement through the removal of soil water by transpiration and by the mechanical reinforcement of their roots. To assess the magnitude of this reinforcement on natural slope stability, direct shear tests were made on dry sand reinforced with different array types of roots. Pinus koraiensis was used as root specimens. The peak shear resistance at each normal stress level was measured on the rooted and unrooted soil specimens. Increased soil resistance(${\Delta}S$) by roots was calculated using parameters like internal friction angle and cohesion of tested soil and also evaluated the effects of root array in tested soil. As results, we find that shear resistance increased in tested soil shear box as diameters and arrayed numbers of root specimen increased and cross root array in tested soil had a much greater reinforcing effect than other root arrays. Comparison of traditional root-soil model with experiments showed that simulated reinforce strength by the model was different with those obtained by the experiment due to its linearity.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.5-18
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• 2010

In this paper, a 3-dimensional stiffened plate model for soil-metal box structures is proposed. 3-dimensional stiffened plate model is enable to model corrugated steel plates of soil metal box culverts considering section modulus and section properties of longitudinal and horizontal direction from a corrugated steel plate. Loading conditions which causes maximum displacement and maximum moment according to the step construction stages(a back filling to the top of the plate, a back filling to the maximum depth of cover, and loading of live loads) was applied and the behaviors of the soil metal box culverts was analyzed. Analysis results of 3-dimensional stiffened model were compared with those of 2-dimensional model, 3-dimensional equivalent plate model and 3-dimensional corrugated plate model. As results, the behaviors of 2-dimensional model and 3 dimensional equivalent model are different from 3-dimensional corrugated plate model but the result of 3-dimensional stiffened model has good agreement with that of 3-dimensional corrugated plate model.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.209-219
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• 2022

To experimentally investigate the variation of soil characteristics in slope during rainfall and the shape of slope failure, the model test was performed using soil box and artificial rainfall simulator. The model test of slope formed by the homogenous sand was performed, and the saturation pattern in the model slope due to rainfall infiltration was observed. The slope model with the inclination of 35° was set up on the slope of 30°, and the rainfall intensity of 50 mm/hr was applied in the test. The soil depth of 35 cm was selected by considering the size of soil box, and the TDR (time domain reflectometry) sensors were installed at various depths to investigate the change of soil characteristics with time. As the result of model test, the slope model during rainfall was saturated from the soil surface to the subsurface, and from the toe part to the crest part due to rainfall infiltration. That is, the toe part of slope was firstly saturated by rainfall infiltration, and then due to continuous rainfall the saturation range was enlarged from the toe part to the crest part in the slope model. The failure of slope model was started at the toe part of slope and then enlarged to the crest part, which is called as the retrogressive failure. At the end of slope failure, the collapsed area increased rapidly. Also, the mode of slope failure was rotational. Meanwhile, the slope failure was occurred when the matric suction in the slope was reached to the air entry value (AEV) estimated in soil-water characteristic curve (SWCC).

• Structural Engineering and Mechanics
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• v.26 no.5
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• pp.545-556
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• 2007

In this paper, a hybrid boundary element technique is implemented to analyze nonlinear transient pile soil interaction in Gibson type nonhomeogenous soil. Inelastic modeling of soil media is presented by introducing a rational approximation to the continuum with nonlinear interface springs along the piles. Modified $\ddot{O}$zdemir's nonlinear model is implemented and systems of equations are coupled at interfaces for piles and pile groups. Linear beam column finite elements are used to model the piles and the resulting governing equations are solved using an implicit integration scheme. By enforcing displacement equilibrium conditions at each time step, a system of equations is generated which yields the solution. A numerical example is performed to investigate the effects of nonlinearity on the pile soil interaction.

• Journal of Ocean Engineering and Technology
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• v.14 no.3
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• pp.61-65
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• 2000

The estimation of soil stabilization is of great importance concerning the construction of structures on weak soil. A typical model of soil stabilization is considered as replacement, which is based on ground at failure due to direct loading on weak soil. The calculation of the line of predicting settlement was carried out using RPL and DIKE programs. The DIKE program is showing a tendency to excel totally about this embankment of the seadike. Hereafter, This program will be contributed widely to the construction of offshore structures on weak soil.

• Structural Engineering and Mechanics
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• v.45 no.5
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• pp.655-676
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• 2013

In this study, strength reduction factors and inelastic displacement ratios are investigated for SDOF systems with period range of 0.1-3.0 s considering soil structure interaction for earthquake motions recorded on soft soil. The effect of stiffness degradation on strength reduction factors and inelastic displacement ratios is investigated. The modified-Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. The effect of negative strain - hardening on the inelastic displacement and strength of structures is also investigated. Soil structure interacting systems are modeled and analyzed with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. New equations are proposed for strength reduction factor and inelastic displacement ratio of interacting system as a function of structural period($\tilde{T}$, T) ductility (${\mu}$) and period lengthening ratio ($\tilde{T}$/T).