• Geomechanics and Engineering
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• v.17 no.3
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• pp.271-278
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• 2019

In recent years, the crack accidents of earth and rockfill dams occur frequently. It is urgent to study the tensile strength and tensile failure mechanism of the gravelly soil in the core for the anti-crack design of the actual high earth core rockfill dam. Based on the self-developed uniaxial tensile test device, a series of uniaxial tensile test was carried out on gravelly soil with different gravel content. The compaction test shows a good linear relationship between the optimum water content and gravel content, and the relation curve of optimum water content versus maximum dry density can be fitting by two times polynomial. For the gravelly soil under its optimum water content and maximum dry density, as the gravel content increased from 0% to 50%, the tensile strength of specimens decreased from 122.6 kPa to 49.8 kPa linearly. The peak tensile strain and ultimate tensile strain all decrease with the increase of the gravel content. From the analysis of fracture energy, it is proved that the tensile capacity of gravelly soil decreases slightly with the increasing gravel content. In the case that the sample under the maximum dry density and the water content higher than the optimum water content, the comprehensive tensile capacity of the sample is the strongest. The relevant test results can provide support for the anti-crack design of the high earth core rockfill dam.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.5-14
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• 2010

Recent researches on the behavior of gravelly soils have been focused mainly on the relative density or on the gravel content. And some researchers presented the liquefaction behavior based on the relative density whereas others based on the gravel content of gravelly soil. However the relative densities vary with gravel content and relative density is not enough to fully express the behavior of gravelly soils. Therefore in this research state parameter which considers void ratio and effective confining pressure is introduced and Steady State Line(SSL) of gravelly soils for various gravel content are determined by undrained triaxial tests in order to express the behavior of gravelly soils. From the research the position of SSL moved downward with gravel content. And the same density of soil showed dense sand behavior or loose sand behavior depending upon the confining pressure. Especially relative density 80% of gravelly soil showed loose sand behavior under high confining pressure. However the gravelly soils with similar state parameters showed similar stress behaviors. It can bee seen that state parameter is useful tool to evaluate undrained behavior of gravelly soils. Also state parameter and undrained strength showed good correlations.

• Journal of Korea Water Resources Association
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• v.32 no.3
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• pp.215-223
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• 1999

Recently, measurement of soil moisture contents using TDR (time domain reflectometry) has been proven to be viable technique. The first empirical model proposed by Topp et al. (1980) has been widely used to determine moisture contents of soils from the TDR-measured dielectric constants. However, applicability of the model was limited to medium-textured soils. In this study, we investigate the applicability of the model to sandy-gravelly soils. Calibration experiments consisted of measurement on travel time of electromagnetic waveform along the parallel TDR rods inserted into samples and gravimetric determination of soil moisture contents. The experiments are performed for two sets of samples different in the length and each set consisted of seven different particle size distributions with various gavel contents. The calibration results show that the Topp equation overestimated the measured moisture content for a given dielectric constant by 3 to 8%. We therefore propose new empirical relationships valid for sandy-gravelly soils.

• Journal of Environmental Impact Assessment
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• v.12 no.1
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• pp.9-22
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• 2003

To consider environmental characteristics in the scope of geochemistry of streams, Hwasun area, soil, sediment and water samples near/in the streams were analyzed in texture and metal contents of soil and sediment and in quality in water. From those analyses, the soils are loamy sand, sandy loam, loam and silty loam in texture. And, the sediments are slightly gravelly sand, gravelly sand and gravelly muddy sand in facies. Metal contents in soils and sediments are of high near Hwasuneup and Hwasun coalfield. In peculiar, P, Co, Li, Ni, Zn and Pb exceed over crust mean contents. Physico-chemistry of above streams according to pH-Eh and Piper's diagrams indicates that the streams are, typically, assigned to natural river water. Water qualities of BOD, T-N and T-P in areas near Hwasun coalfield, Dongmyeon and Hwasuneup are polluted over V level. Enrichment factor(EF) representing metal condensation in P, Cu, Zn and Pb appear near Hwasun coalfield and Hwasuneup from the soil and sediment samples, in part. Additionally, river water in dry season is very high in BOD, T-N, $Na^+$ and ${SO_4}^{2-}$. It is suggested that the relatively high metal contents in the stream be connected with above coalfield and urban areas.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.27-44
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• 2022

Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".

• Journal of Biosystems Engineering
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• v.34 no.4
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• pp.205-210
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• 2009

It has been known from Willoughby's empirical equation that rating cone index can be determined if wheel sinkage and slip of a vehicle can be measured on soil surface. A field data of wheel sinkage and slip was collected from two tractors of different sizes on gravelly sand and gravelly loamy sand. Using the data, rating cone index of the soil was estimated. The estimated rating cone index demonstrated that it could be determined in real time by measuring wheel sinkage and slip. It was also demonstrated statistically that the same soil strength could be obtained under the same soil conditions regardless of the vehicle platforms used for the wheel sinkage and slip measurements.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.33-41
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• 2011

In this study, it conducted a compaction quality control test in 29 domestic construction sites and investigated the relationship between classical method (Cyclic Plate bearing test) and LFWD test with subgrade materials which consist in sandy soil and gravelly soil. According to the test results, the most of soil types were mostly satisfied with specification criterion and gravelly soils were easily satisfied with values over 3 times greater than specification criterion. In term of the correlation relation of soil modulus with the two compaction quality control test methods, it is shown that the sandy soil types were a good correlation, while gravelly soil types with a high stiffness materials were indicated less correlation. After the compensation for stress condition, a linear regression for elastic modulus were higher correlation.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.637-648
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• 2023

When an earth pressure balance (EPB) shield machine bores a tunnel in gravelly sand stratum, the excavated natural soil is normally transformed using foam and water to reduce cutter wear and the risk of direct muck squeezing out of the screw conveyor (i.e., muck spewing). Understanding the undrained shear behavior of conditioned soils under pressure is a potential perspective for optimizing the earth pressure balance shield tunnelling strategies. Owing to the unconventional properties of conditioned soil, a pressurized vane shear apparatus was utilized to investigate the undrained shear behavior of foam-conditioned gravelly sands under normal pressure. The results showed that the shear stress-displacement curves exhibited strain-softening behavior only when the initial void ratio (e₀) of the foam-conditioned sand was less than the maximum void ratio (e_max) of the unconditioned sand. The peak and residual strength increased with an increase in normal pressure and a decrease in foam injection ratio. A unique relation between the void ratio and the shear strength in the residual stage was observed in the e-ln(τ) space. When e₀ was greater than e_max, the fluid-like specimens had quite low strengths. Besides, the stick-slip behavior, characterized by the variation coefficient of measured shear stress in the residual stage, was more evident under lower pressure but it appeared to be independent of the foam injection. A comparison between the results of pressurized vane shear tests and those of slump tests indicated that the slump test has its limitations to characterize the chamber muck fluidity and build the optimal conditioning parameters.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1258-1263
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• 2011

This study was conducted to reclassify Asan series based on the second edition of Soil Taxonomy and to discuss the formation of Asan series distributed on the rolling to hilly areas. Morphological properties of typifying pedon of Asan series were investigated and physico-chemical properties were analyzed according to Soil survey laboratory methods manual. The typifying pedon of Asan series has dark yellowish brown (10YR 4/4) gravelly loam Ap horizon (0-18 cm), strong brown (7.5YR 5/6) gravelly clay loam BA horizon (18-30 cm), red (2.5YR 4/6) gravelly clay loam Bt1 horizon (30-52 cm), red (2.5YR 4/8) gravelly clay loam Bt2 horizon (52-98 cm), and red (2.5YR 4/8) gravelly clay loam C horizon (98-160 cm). The typifying pedon has an argillic horizon from a depth of 30 to 98 cm and a base saturation (sum of cations) of less than 35% at 125 cm below the upper boundary of the argillic horizon. It can be classified as Ultisol, not as Inceptisol. It has udic soil moisture regime, and can be classified as Udult. Also that meets the requirements of Typic Hapludults. It has 18-35% clay at the particle-size control section, and has mesic soil temperature regime. Therefore Asan series can be classified as fine loamy, mesic family of Typic Hapludults, not as fine loamy, mesic family of Typic Dystrudepts. Asan series occur on rolling to hilly areas in residual materials derived from granite gneiss, schist, and gneiss rocks. They are developed as Ultisols with clay mineral weathering, translocation of clays to accumulate in an argillic horizon, and leaching of base-forming cations from the profile for relatively long periods under humid and temperate climates in Korea.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.2
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• pp.159-170
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• 1998

This study was initiated to investigate the applicability of the dredged soil from agricultural reservoirs on the crop cultivation. Four reservoirs were selected for this experiment, and properties of the dredged soils were analyzed physically and chemically. Soil textures were sandy loam(SL), silty loam(SiL), gravelly loam(GL), graveHy silty loam(GSiL), respectively. General chemical components, organic matter contents, main cations, heavy metals, etc. showed no adverse effects on crop growth. Tomato, cucumber, radish, Chinese cabbage were cultivated during 8 months period, in the soil treated with fertilizer and compost(Tmt.1), fertilizer(Tmt.2), compost(Tmt.3) and none (Tmt.4). Data for plant height, root zone depth and crop yield were collected and analyzed, and the yield for most crops showed increase as Tmt.1 >Tmt.2>Tmt.3>Tmt.4 by fertilizing methods, and as GL>GSiL>SL>SiL by soil textures. From the results, the crop cultivation using dredged soil was considered to be effective, due to its soil texture, organic matter content and fertilization.