• The Journal of Engineering Geology
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• v.29 no.4
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• pp.383-391
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• 2019

Bio-grouting based on microbial-induced calcite precipitation (MICP) is recently emerging as a novel and environmentally friendly technique for improvement of coarse-grained ground. To date, the mechanical behaviour of bio-grouted coarse-grained soil with different calcite contents and grain sizes still remains poorly understood. The primary objective of this study is to investigate the influence of calcite content on the mechanical properties of bio-grouted coarse-grained soil with different grain sizes. This is achieved through an integrated study of uniaxial loading experiments of bio-grouted coarse-grained soil, 3D digitization of the grains in conjunction with discrete element modelling (DEM). In the DEM model, aggregates were represented by clump logic based on the 3D morphology digitization of the typical coarse-grained aggregates while the CaCO₃ was represented by small-sized bonded particle model. The computed stress-strain relations and failure patterns of the bio-grouted coarse-grained soil were validated against the measured results. Both experimental and numerical investigation suggest that aggregate sizes and calcite content significantly influence the mechanical behaviour of bio-cemented aggregates. The strength of the bio-grouted coarse-grained soil increases linearly with calcite content, but decreases non-linearly with the increasing particle size for all calcite contents. The experimental-based DEM approach developed in this study also offers an optional avenue for the exploring of micro-mechanisms contributing to the mechanical response of bio-grouted coarse-grained soils.

• Macromolecular Research
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• v.15 no.7
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• pp.610-616
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• 2007

We developed a coarse-grained force field and have extended it to polystyrene with longer chain length. A systematic method was introduced and was utilized to explain how the coarse-grained force field for polystyrene could be developed from the atomistic simulation in the paper. We elected to use polystyrene with different chain lengths of 20, 40 and 80 monomers in this study. In three cases, we utilized the same new mapping scheme. The coarse-grained force field does reproduce the bond, angle, and radial distribution of the atomistic model. The coarse-grained model proved successful, as shown by analyses of the static and dynamic properties of different chain lengths.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.183-194
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• 2023

This study presents the prediction of the California bearing ratio (CBR) of coarse- and fine-grained soils using artificial intelligence technology. The group method of data handling (GMDH) algorithm, an artificial neural network-based model, was used in the prediction of the CBR values. In the design of the prediction models, various combinations of independent input variables for both coarse- and fine-grained soils have been used. The results obtained from the designed GMDH-type neural networks (GMDH-type NN) were compared with other regression models, such as linear, support vector, and multilayer perception regression methods. The performance of models was evaluated with a regression coefficient (R²), root-mean-square error (RMSE), and mean absolute error (MAE). The results showed that GMDH-type NN algorithm had higher performance than other regression methods in the prediction of CBR value for coarse- and fine-grained soils. The GMDH model had an R² of 0.938, RMSE of 1.87, and MAE of 1.48 for the input variables {G, S, and MDD} in coarse-grained soils. For fine-grained soils, it had an R² of 0.829, RMSE of 3.02, and MAE of 2.40, when using the input variables {LL, PI, MDD, and OMC}. The performance evaluations revealed that the GMDH-type NN models were effective in predicting CBR values of both coarse- and fine-grained soils.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.3
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• pp.57-69
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• 1989

The study was carried out for the strength parameter of coarse grained Soil and slope stability analysis of earth dam. The test samples were taken fifteen kinds of soil from cohesive soil to coarse gravel. The degree of compaction of test samples for shear test and permeability test was chosen 95 percentage of maximum dry density. The results of this study are as follows ; 1.The maximum dry density(Yd) of coarse grained soil increase in proportion to coarse particles(P) with the relation of Y d= 1.609+0.0043P. 2.The coefficients of permeability(k) decrease by the increase of fine particles(n) with the relation of k=0.0426e-0 185n. 3.The cohesions of soil decrease by the increase of coarse particles, but internal friction angles are more increased in same condition. 4.The internal friction angles(${\Phi}$) decrease in inverse proportion to void ratio(e) with the relation of ${\Phi}$ = 73.068 - 69.268e. 5.The strength parameters( Ct ${\Phi}$t) by triaxial compression test are clearly smaller than that (Cd, ${\Phi}$d) by direct shear test in fine grained soil, but the differences between both parameters are a little in coarse grained soil.The relations of both parameters are as follows; Ct = O.544Cd + 0.04 ${\Phi}$t= 1.282${\Phi}$d-2306 6.In cohesive soil, the strength parameters( Cl ${\Phi}$l) by large size shear test apparatus are similar to the strength parameters(Cs , ${\Phi}$s) by small size shear test appratus, but Cs and ${\Phi}$s values are larger than Cl and ${\Phi}$l values from 10 percentage to 20 percentage in coarse grained soil. 7.The fine grained soil is inappropriate to high dam more than 20 meters and it must be taken coarse grained soil with high internal friction angle for high dam.

• Journal of the korean society of oceanography
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• v.32 no.3
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• pp.128-137
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• 1997

This study presents results from a detailed sedimentological investigation of surface sediments obtained from the Korea Strait region, the southern part of the East Sea (Sea of Japan). The distribution of different types of bottom sediments is controlled by the recent fine-grained sediment transport and deposition combined with the lowerings of sea level during the last glacial period, forming a diverse mixture of organic-rich fine-grained and shelly coarse-grained sediments. In comparison to high organic concentration of fine-grained sediments in the inner continental shelf and slope areas, the shell-rich coarse-grained sediments on the outer shelf are discernible being further modified. These coarse-grained sediments are confirmed as relict resulting from the sediment dynamics during the lower sea levels of the last glacial period. Clay mineral distribution of the fine-grained sediments gives information about the transport mechanism. Presence of present-day current system (the Tsushima Warm Current) is most probable source for the fine-grained particles into the open East Sea from the East China Sea, indicating that Holocene sediment dynamics may be used to explain the observed distribution of surface coarse-grained shell-rich sediments.

• Journal of the Mineralogical Society of Korea
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• v.19 no.1 s.47
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• pp.31-38
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• 2006

Site environments bring about various different deterioration forms of stone cultural properties. The aim of this study is to document the influence of coarse grained sandy soil on the deterioration of stone cultural properties. Bulguksadabotap is a good example that demonstrates the problem with coarse grained sandy soil. The ground around the Bulguksadabotap is covered with coarse grained sandy soil and the pagoda is surrounded by the corridors. Coarse grained sandy soil float easily in the air and deposit in the complicated stone structure caused by strong wind in Gyeongju and numerous visitors. To explain the influence of coarse grained sandy soil on the deterioration, the coarse grained sandy soil and weathered stone pieces of Bulguksadabotap were analyzed by XRD, optical microscopy, SEM for mineralogical component and IC and ICP-AES for the soluble salts. The soil and weathered stone pieces include clay minerals, such as smectite and kaolinite, can expand with water and exert pressure on the stone. Small size of the clay minerals in the coarse grained sandy soil can easily penetrate into the weathered surfaces of the Bulguksadabotap. The weathered stone pieces also contain NaCl, which is known to contribute to increase the expandibility of clay minerals by providing with $Na^{+}$ or by dropping the equilibrium of relative humidity. These results indicates that coarse grained sandy soil is not proper to site environment for weathered stone cultural properties.

• Journal of the Korean Society for Nondestructive Testing
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• v.10 no.1
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• pp.18-23
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• 1990

In materials with the large grain size, ultrasonic waves are highly attenuated by the grain boundary acting as scattering centers due to discontinuity of elastic constant. In this study, the improved probes were developed so that they minimized the effect of grain scattering in order to detect deep flaws in coarse grained materials. As the result, the developed ultrasonic transducers showed the better sensitivity and signal to noise ratio when compared with the commercial probes in testing the interior of coarse grained material.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.325-333
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• 2001

The effect of base metal grain size on isothermal solidification behavior of Ni-base superalloy, CMSX-2 during transient liquid phase (TLP) bonding was investigated employing MBF-80 insert metal. TLP-bonding of single crystal. coarse-grained and fine-grained CMSX-2 was carried out at 1373∼1548k for various holding time in vacuum. The eutectic width diminished linearly with the square root of holding time during isothermal solidification process for single crystal, coarse-grained and fine-grained base metals. The completion time for isothermal solidification decreased in the order ; single crystal, coarse-grained and fine-grained base metals. The difference of isothermal solidification rates produced when bonding the different base metals could be explained quantitatively by the effect of base metal grain boundaries on the apparent average diffusion coefficient of boron in CMSX-2.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.777-783
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• 2006

The coarse grained materials are used in various construction field such as express way back fill, Dam etc. Especially, for dam construction, a huge mount of rock fill materials are needed, so around domestic stony mountains are generally developed to produce materials. Not an accurate theory, but design criteria is based on empirical factors that were constructed in advance for design of dam especially Concrete Face Rockfill Dam(CFRD). Considering the post facts, the modified design criteria are essential in the future with more theoretical and experimental ways. In this study, large scale direct shear tests are performed with various relative density conditions on coarse grained material of Yecheon area to compare test results and general CFRD design factors.

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.11-19
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• 2013

Coarse-grained soils are typical engineering materials commonly used in many civil engineering applications such as structural fills, subgrade and drainage fills for dam, railway and bridge. Various researches have been performed with related to constitutive laws for numerical analysis of such structures. This paper presents a parametric study for a constitutive model for coarse grained materials. The model is a kind of the bounding surface models based on critical state theory. A distinct feature of the model is to capture the response of coarse-grained materials with different void ratios and confining pressures using a single set of model parameters. The model behavior is defined with a set of elastic parameters, critical state parameters, and model-specific parameters. The parametric study was performed for the model-specific parameters. The result of parametric study shows that the model is capable to capture stress-dilatancy behavior and kinematic-hardening under non-associative plastic flow.