• Explosives and Blasting
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• v.22 no.2
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• pp.45-54
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• 2004

Samples examined in this study were acquired from Machun building stone, Dukwoo building stone in Kyungnam province The aim of this study is to examine physical features of Machun rock from specific gravity, porosity. absorption, point load test. triaxial compressive test, Brazilian test, petrology test, and chemical analysis test.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.217-223
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• 2000

Microcracks that consist of quarry planes of granite are an essential factor affecting the long-term behavior of granite. In this paper, fine-grained granite distributed in the Tsukuba area of Japan was selected and microcracks were measured by using scanline method. In addition, a new relaxation testing equipment was developed to carry out stress relaxation test under water-saturated triaxial condition. Based on the relaxation test results with the initial stress level of 75%, the axial stress is decreased by 39%-49% just after the start of the tests, and the totally relaxed stress is 10∼24 MPa in 190 ERT (Elapsed relaxation time, hour). In addition, the relaxed stress is increased with the density of cracks which are parallel to axial load direction.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.529-536
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• 2005

Based on an estimating method for post-cyclic strength and stiffness with cyclic triaxial tests, Direct Simple Shear (DSS) tests were carried out to confirm whether the method can be adapted to DSS test on fine-grained soils: silty clay, plastic silt, and non-plastic silt. Results from post-cyclic DSS tests were interpreted by a modified method as adopted for post-cyclic triaxial tests. In particular, influence of plasticity index for fine-grained soils was emphasised. Findings obtained from the present study are: (i) the higher the plasticity index of fine-grained soils is, the less not stiffness ratio but strength ratio decreases with increment of a normalised excess pore water pressure; and (ii) post-cyclic strength and stiffness results from DSS tests agree well with those predicted by the method modified from a procedure used for triaxial test results.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.55-60
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• 2010

Rockfill zones in CFRD consist typically of large granular materials, usually the maximum particle size up to several meters, which makes laboratory testing to determine the mechanical properties of rockfill difficult. Commonly, the design strength of the rockfills is obtained by scaling down the original rockfill materials and performing laboratory strength tests for the reduced size materials. The objective of the present study is to investigate the effect of particle size on the shear behavior and the strength for granular materials. A series of large-scale triaxial tests was conducted on large granular materials with the maximum particle size varying from 20 to 50mm. The test results showed that overall shear behaviors were similar between the samples with different particle sizes while there were slight differences in the magnitudes of the peak shear stress between the samples. In addition, a simulation of the granular material with the max. particle size of 20mm was performed using DEM code, $PFC^{2D}$, and compared with the test results. The deviatoric stress versus strain behaviors of experimental and numerical tests were found to be matched well up to the peak stress state.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.998-1003
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• 2008

It has been recognized unsaturated soil behaviour playing an important role in geomechanics. Up to now, only a few experimental data are available for the technical difficulties related to both volume changes and suction measurements. In this study, the volume changes of unsaturated compacted silty soil were monitored with proximeter (i.e. non-contactable transducer) during various triaxial compression tests, which gave a realistic estimation in the volume changes of unsaturated soil sample. Various triaxial compression tests for unsaturated soil under different drainage conditions are carried out. The behaviour of the pore pressure, namely, the pore-air pressure and the pore-water pressure, and matric suction during the shearing tests are investigated. The experimental results have revealed that the mechanical behaviour of unsaturated soil can be significantly affected by the matric suction.

• Journal of the Korean Society for Railway
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• v.20 no.1
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• pp.64-75
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• 2017

The role of a track subgrade is to provide bearing capacity and distribute load transferred to lower foundation soils. Track subgrade soils are usually compacted by heavy mechanical machines in the field, such that sometimes they are attributed to progressive residual settlement during the service after construction completion of the railway track. The progressive residual settlement generated in the upper part of a track subgrade is mostly non-recoverable plastic deformation, which causes unstable conditions such as track irregularity. Nonetheless, up to now no design code for allowable residual settlement of subgrade in a railway trackbed has been proposed based on mechanical testing, such as repetitive triaxial testing. At this time, to check the DOC or stiffness of the soil, field test criteria for compacted track subgrade are composed of data from RPBT and field compaction testing. However, the field test criteria do not provide critical design values obtained from mechanical test results that can offer correct information about allowable permanent deformation. In this study, a test procedure is proposed for permanent deformation of compacted subgrade soil that is used usually in railway trackbed in the laboratory using repetitive triaxial testing. To develop the test procedure, an FEA was performed to obtain the shear stress ratio (${\tau}/{\tau}_f$) and the confining stress (${\sigma}_3$) on the top of the subgrade. Comprehensive repetitive triaxial tests were performed using the proposed test procedure on several field subgrade soils obtained in construction sites of railway trackbeds. A permanent deformation model was proposed using the test results for the railway track.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.5-17
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• 2010

Coarse granular material is used as important fill material in most of large embankments such as railway, road, dam and so on. Therefore, the accurate design parameters of the coarse granular material are necessarily required in design and construction. The behavior of the coarse granular material was not well understood because of the lack of large testing equipment capable of coarse granular material. A large triaxial testing system was developed in this research, capable of large specimens of 500 mm, 300 mm and 150 mm in diameter. In the new large triaxial testing system, the load cell is installed inside the triaxial cell and axial displacement is measured locally on a specimen in order to improve control and measurement in small strain level. Urethane specimens of 300 mm and 50 mm in diameter were prepared. The large triaxial tests were performed on the 300 mm diameter urethane specimens while RC/TS and impact echo tests on the 50 mm diameter urethane specimens to verify this testing system. In this verification test results, we could ascertain the reasonable test results of the KRRI large triaxial testing system.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.133-152
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• 1999

The cyclic triaxial test was carried out to research liquefaction characteristics and sample disturbance effects of silty sand soils at the west coast in Korea. First, liquefaction in silty sand was generated when axial strain approached to $\pm10%$ of strain and behavior of pore pressure was similar to the formula suggested by Seed, Martin, and Lysmer(1975). Also, it was found that dilatancy was generated at failure. Secondly, the liquefaction evaluation methods suggested by many researchers were carried out and the results were compared. In these methods the weak depth in liquefaction was similar and the method carried out by cyclic triaxial test on remolded sample showed the least safety factor. Thirdly the stress ratio by cyclic triaxial test was compared with that obtained from SPT N-value as a kind of empirical methods. It was found that the effect of sample disturbance was relatively small when SPT N-value was less than 20, but there were large differences in safety factor and resistance of liquefaction in soil by the effects of disturbance and remolding when SPT N-value was more than 20.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.43-51
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• 2014

In the earth structures of railways, large coarse granular materials are widely used as fill materials. However, experimental studies that consider the dynamic properties of these coarse granular materials have rarely been carried out in Korea due to the lack of a large scale test apparatus in this country. In this study, large scale cyclic triaxial tests were carried out for materials such as reinforced roadbed (subballast, graded crushed stone), transition zone gravel, and the upper subgrade of a railway. These specimens were prepared according to certain conditions (dry unit weight, grain size distribution, and so on) specified in the Korea railroad design standard. Based on these large triaxial test results, normalized shear modulus and damping ratio curves according to small strain level are suggested. A model and coefficients for each material are also proposed.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.7-15
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• 2022

Most studies have conducted cryogenic triaxial compression tests with frozen specimens prepared in a separate mold by one-directional freezing. This method has the potential to generate residual stress in a frozen specimen and cannot be adopted to simulate the application of the artificial ground freezing method in the field. Therefore, in this study, novel equipment and procedure for the cryogenic triaxial compression test were proposed to overcome the limitations of existing test methods. Therefore, the mechanical characteristics of frozen sand, considering the effect of temperature and confining pressure, were evaluated. As the freezing temperature decreased, the brittleness of frozen sand increased, and the strength increased due to a decrease in the unfrozen water content and an increase in the ice strength. A higher confining pressure resulted in an increase in interparticle friction and the pressure melting phenomenon, which caused strength reduction. Thus, it was found that the mechanical behaviors of frozen sand were simultaneously affected by both temperature and confining pressure.