• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.247-254
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• 2003

While the interests in the environmental problem during the construction are increasing, the use of low noise-vibration auger-drilled pilling is increasing to solve noise and vibration problem in pilling. Therefore, in Korea, SIP (Soil-Cement Injected Precast Pile) method is mainly used as auger-drilled pilling. However, there is no proper design criteria compatible with the ground condition of Korea, so which is most wanted. To improve and supplement this situation, direct shear tests for the friction between SIP pile skin interface and soil were executed on various conditions. Through the analysis of test results, skin friction characteristics of SIP were investigated thoroughly Also, hyperbolic model parameter fomulas which describe the friction behavior and the new non-linear unit skin friction capacity model with SM, SC soil were suggested.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.281-293
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• 2002

Empiricism has characterized the traditional methods of pile design; in essence, pile design recommendations are based on the accumulated knowledge of pile behaviour based on the construction and subsequent load testing of piles in soil and rock. In this paper, the traditional approaches to design of piles in rock will be briefly reviewed. It will be shown that the unrelated empirical relationships developed fur rock lead to considerable uncertainty in the design of piles. A new method for predicting the shaft resistance of piles socketed into rock, and based on fundamental principles is outlined. It is shown that the shaft resistance predictions of this method agree well with the field test data for rock and hard soil. It is demonstrated by way of a limited parametric study that shaft roughness and socket diameter are critical factors in the performance of piles constructed in these materials. The application of the method to piles socketed into the granites and gneisses of Korea is discussed by way of a case study and by reference to recent direct shear tests on these rocks.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.3-10
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• 2010

Case study was carried out on the interpretation of the mechanical behavior of a severely damaged reinforced earth wall comprising geotextile with the concrete panel facing. In this part I, the outline of the damaged reinforced earth wall is in detail described. The background and cause of the damage are discussed based on the results of site investigation. The engineering properties of the fill were examined by performing various in-situ and laboratory tests, including the surface wave survey (SWS), PS-logging, RI-logging, soaking test, the direct shear box (DSB) test, bender element (BE) test, etc. The background as well as the cause for the damage of the wall may be described such that i) a considerable amount of settlement took place over a 3m thick weak soil layer in the lower part of the reinforced earth due to seepage of rainfall water, ii) the weight of the upper fill was partially supported by the geo-textile hooked on the concrete panels (n.b., named conveniently "hammock state" in this paper), and iii) the concrete panels to form the hammock were severely damaged by the unexpectedly large downwards compression force triggered by the tension force of the geotextile. The numerical simulation for the hammock state of the wall, together with counter-measures to re- stabilize the wall is subsequently described in Part II.

• Geomechanics and Engineering
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• v.37 no.2
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• pp.123-133
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• 2024

This study investigates the effects of loading frequency (f) and specimen size on the liquefaction resistance of clean sand. A series of cyclic direct simple shear tests were conducted on Jumunjin sand with varying consolidated relative densities (40% and 80%), f values (0.05, 0.10, and 0.20 Hz), and diameter to height (D/H) ratios (3.63, 3.18, 2.82, and 2.54). The results demonstrated the significant influence of f and D/H ratio on the number of cycles to liquefaction (N_cyc-liq) and the cyclic resistance ratio (CRR₁₅). It was observed that increasing f linearly increased N_cyc-liq. Increasing the specimen height also led to higher N_cyc-liq values irrespective of the f or relative density. Moreover, a positive correlation between CRR₁₅ and f indicated that higher f yielded higher CRR₁₅. This relationship was more pronounced in dense sand than in loose sand. Specimen height also significantly affected CRR₁₅, with increasing the specimen height resulting in higher CRR₁₅ values. Furthermore, the effect of f on CRR₁₅ was less significant compared to the influence of specimen height. The effect of f on the normalized cyclic resistance ratio (NCRR) was relatively negligible for loose sand but more substantial for dense sand depending on the D/H ratio. Data analysis revealed that the NCRR generally decreases as the D/H ratio increases. An interpolation formula was provided to calculate the NCRR based on the D/H ratio regardless of the f and relative density.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.85-94
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• 2011

Mixtures of sand and rubber particles ($D_{sand}/D_{rubber}=1$) are investigated to explore their characteristics under different stain level. Mixtures are prepared with different volumetric sand fractions ($sf=V_{sand}/V_{total}$). Experimental data are gathered from a resonant column, an instrumented oedometer, and a direct shear tests. Results show that sand and rubber differently control the behavior of the whole mixture with strain level. Non-linear degradation of small strain stiffness is observed for the mixtures with $sf{\geq}0.4$, while the mixtures with low sand fraction ($sf{\leq}0.2$) show significantly high elastic threshold strain. Vertical stress-deformation increases dramatically when the rubber particle works as a member of force chain. The strength of the mixtures increases as the content of rubber particle decreases, and contractive behavior is observed in the mixtures with $sf{\leq}0.8$. Rubber particle plays different roles with strain level in the mixture: it increases a coordination number and controls a plasticity of the mixture in small strain; it prevents a buckling of force chain in intermediate strain; it leads a contractive behavior in large strain.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.344-351
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• 2010

Slip along a frictional fracture can be approached as initiation and propagation of a mode II crack along its own plane. Fracture mechanics theories predict that under pure mode II loading initiation will occur when the energy release rate of the fracture attains a critical value ($G_{IIC}$), which is generally taken as a material property. For the past few years the rock mechanics group at Purdue University has investigated experimentally the dependence of $G_{IIC}$ on normal stress and on the frictional characteristics of a fracture. A number of experiments has been conducted first on acrylic, a material that, using photoelastic methods, allows visualization of the stress field ahead of the fracture tip; and later on gypsum, a rock model material with relatively low unconfined compression strength. The experimental investigation has been expanded to include other frictional materials with higher unconfined compression strength. Direct shear tests have been conducted on specimens made with cement paste. New observations together with previous experiments indicate that $G_{IIC}$ can only be considered a material property when the peak friction angle of the discontinuity is similar to the residual friction angle; otherwise the critical energy release rate increases with normal stress.

• Journal of the Korean GEO-environmental Society
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• v.11 no.6
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• pp.85-91
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• 2010

As enormous construction projects of land development are carried out around Korea, useful construction materials are needed to perform the construction projects. However, there are no more enough of fill and reclamation materials in our country. That is why the coal ash is expected to be utilized as an alternative material. Since the coal ash has the characteristics of a pozzolan and a selfhardening material, it is adjudged that coal ash has a great possibility to be used as a fill and reclamation material. In this study, grain size analysis, Atterberg limit test, and specific gravity test were performed to examine the physical characteristics of the coal ash about a self-hardening material before utilizing the coal ash in the construction. Compaction test, unconfined compression test, direct shear test, and flexible wall permeability test were conducted to investigate the engineering characteristics according to mixture ratios of fly ash and bottom ash. As a result of the tests, it was confirmed that the mixing ratio 1:1 of fly ash and bottom ash is the most effective to use as a fill and reclamation material. If the mixture of coal ash is used as a backfill material with light weight around structure, it is expected to play a significant role in reducing earth pressure on the back of the structure. As the age of the mixture of coal ash goes by, it intends to decrease the coefficient of permeability. As described above, the coal ash should be considered as an alternative material of fill and reclamation materials since the result of the tests indicates that the coal ash is suitable to a useful material on the construction design.

• Journal of the Korean GEO-environmental Society
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• v.12 no.5
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• pp.13-19
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• 2011

The strength of granular mixtures can be controlled by the majority of the mixture, fine grains. However, in some cases, the small amount of gravel in the mixture may influence the strength of the mixture. In this study, the effect of some dispersed gravels on strength of sand is evaluated. Gravels are embedded in the middle of each cemented sand layer. The size and number of embedded gravels varies. After two days curing, a series of unconfined compression tests is performed on the cemented sand with dispersed gravels. In addition to that, a series of direct shear tests is also carried out on clean sand with gravels to evaluate its friction angle. For the specimens with the same ratio of gravel weight of 7% in which gravel size and number are different, an unconfined compressive strength(UCS) of a specimen with gravels decreases up to 15% compared to a specimen without gravel and then increases with increasing gravel number. For specimens embedded with the same size of gravel, UCS decreases and then increases as a number of gravel increases. As a number of gravel increases, a friction angle of clean sand with gravels decreases up to $5^{\circ}$ and then recovers up to that of a specimen without gravel.

• Geotechnical Engineering
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• v.14 no.4
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• pp.61-76
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• 1998

Various kinds of reinforced soil methods have been developed by many researchers or companies for their economic merits mainly. These methods have generally used sandy soils which have high permeability as embanking or backfill material. That is because, if poor embanking materials, especially like a clayey soil which has very low permeability, are used in a reinforced soil embanking, and if excessive pore water pressure is produced by external factors, the friction resistance between reinforcing members and Boils decrease, as a result possible damage or collapse of the body of a reinforced embankment. In fact, clayey Boils can also be used as a embanking materials with reinforcement which has high permeable capacity, and are expected to be able to dissipate the excess pore water pressure effectively. In this study reinforcing effects have been examined through a serries of direct shear tests in which clayey soils are reinforced with nonwoven geotextiles of which permeability is very high and tensile strength is relatively weaker than geogrids which are usually used in reinforced soil wall. Even though such nonwoven geotextile are used as reinforcement of high saturated clayey soils. the test results show the possibility that nonwoven geoteztiles could be used as a reinforcement for reinforced soil walls effectively.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.71-85
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• 2020

To understand behavior of fault cores in the field of geotechnical and geological engineering, we present an investigation of the physical properties (breccia and clay contents, unit weight, porosity, and water content) and friction characteristics (internal friction angle and cohesion) of fault cores, in granitic, sedimentary, and volcanic rocks in South Korea. The breccia contents in the fault cores are positively correlated with unit weight and negatively correlated with clay content, porosity, and water content. The inter-quartile ranges of internal friction angles and cohesion calculated from direct shear tests are 16.7-38.1° and 2.5-25.3 kPa, respectively. The influence of physical properties on the friction characteristics of the fault cores was analyzed and showed that in all three rock types the internal friction angles are positively correlated with breccia content and unit weight, and negatively correlated with clay content, porosity, and water content. In contrast, the cohesions of the fault cores are negatively correlated with breccia content and unit weight, and positively correlated with clay content, porosity, and water content.