• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.75-82
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• 2004

To evaluate the characteristics of permeability in weathered residual soil, flexible wall permeameter tests are performed using undisturbed samples. The Influence of hydraulic gradient and confining pressure on the permeability of weathered residual soil is analyzed. To compare the characteristics of permeability between weathered soil and sand, similar tests are performed using Jumoonjin sand. Also, piping model tests are performed to investigate the piping resistance of weathered residual soil. As a result, weathered residual soil shows very dependable permeability on hydraulic gradient and very large resisting ability against piping compared with sand.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.743-750
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• 2002

Unsaturated soil has a possibility to induce a negative pore water pressure. Until now, saturated soil is mainly focused on the research of soil mechanics. Recently, soil mechanics is researched on two major parts such as saturated and unsaturated soil mechanics. Negative pore water pressure has a non-linear relationship with the water content changes. Soil-water characteristic curves of soil in Korea are not determined. There is no proper characteristic value such as air-entry value and residual water content. In this study, the characteristic curves of reclaimed soil, sand, and weathered granite soil were determined by laboratory tests. Air-entry value and residual water content were determined by fitting methods. Soil-water characteristic curves were estimated based on the particle-size distribution and compared with the laboratory test results. The results of soil-water characteristic curves estimation indicated that Fredlund and Wilson's model is excellent for sand and weathered granite soil. Arya and Paris's model is excellent for reclaimed soil.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.423-430
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• 1999

A weathered residual soil is a soil-like material derived from the in situ weathering and decomposition of rock which has not been transported from its original location. Undisturbed sampling of residual soils is extremely difficult, which has an important effect on investigating the strength and compression characteristics. Thus, a special undisturbed sampling device (direct shear box with shoe) was developed and undisturbed samples were successfully obtained for direct shear tests, Direct shear testing was conducted under unsoaked and soaked condition. As a result, the shear strength of soaked samples was less than that of unsoaked samples, and it was verified that direct shearing of undisturbed samples can evaluate reasonably the shear strength and the slope stability.

• Journal of Industrial Technology
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• v.17
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• pp.119-124
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• 1997

This thesis is an experimental research of shear behavioral characteristics and shear behavioral coefficient of weathered residual soil which is mostly contained in soil of Korea. Using the weathered residual soil from mountain near Kangwon National University, this experimental research were contained the physical properties of sample in term of the basic test method such as specific gravity, plastic and liquid limit, grain-size distribution, density and water content. Experimental results obtained from direct shear test sand triaxial compression tests show that according to step loading, linear strain and linear stress increase continually and angle of internal friction decreases just little according to incresing of water content in case of ignoring the cohesion, and angle of internal friction appears the maximum angle near a optimum moisture content in case of considering the cohesion.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.2
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• pp.80-91
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• 1999

This paper presents the stress-strain , volumetric strain characteristics of the Pocheon weathered residual granite soil with variation of the initial water content under drained conditions. A series of consolidated drained triaxial compressiion tests and isotrpc compression tests with various initial water content on specimens were performed. All material parameters of Lade's double work hardening model were determined by using the results of tests. Most aspects of the soil behavior measured in the triaxial compression tests were reproduced with good accuracy by the constitutive model . Therefore double work hardening model has been shown to be applicable to weathered residual granite soil.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.28-33
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• 2006

Shallow failures of slopes in weathered soils are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the water infiltration. In this paper, hysteresis on soil-water characteristic curve(SWCC) of granite and gneiss weathered soils are investigated using transient flow analysis respectively. Each case was subjected to artificial rainfall intensities and time duration depending on the laboratory-based drying and wetting processes. The results show that the unsaturated seepage on weathered slopes are very much affected by the initial suction of soils and unsaturated permeability of the soils. In addition, a granite weathered soil has a lower air-entry value, residual matric suction, and wetting front suction and less hysteresis loop than a gneiss weathered soil.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.360-372
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• 2005

The weathering degree and shear wave velocity, $V_S$, were evaluated for decomposed granite layers in Hongsung, where earthquake damages have occurred. The subsurface geological layers and their $V_S$ profiles were determined, respectively, from boring investigations and seismic tests such as crosshole, downhole and SASW tests. The subsurface layers were composed of 10 to 40 m thickness of weathered residual soil and weathered rock in most sites. In the laboratory, the weathering indexes with depth were estimated based on the results of X-ray fluorescence analysis using samples obtained from field, together with the dynamic soil properties determined from resonant column tests using reconstituted specimens. According to the results, it was examined that most weathering degrees represented such as VR, Li, CIA, MWPI and WIP were decreased with increasing depth with exception of RR and CWI. For weathered residual soils in Hongsung, the $V_S's$ determined from borehole seismic tests were slightly increased with increasing depth, and were similar to those from resonant column tests. Furthermore, the $V_S$ values were independent on the weathering degrees, which were decreased with depth.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.93-100
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• 1998

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.711-716
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• 2002

When judging the ground by core-logging, depth of coring might be stopped by coming into view of the moderately weathered rock and also considered as bedrock line. However, highly weathered rock may appear again, if coring more, because there are core-stones in the residual soil and highly weathered rock by the effect of hydraulic-thermal differentiation and does the irregular rock weathering or metamorphic rock region. Therefore, there are room for misunderstanding of diagnosing the moderately weathered rock. Even though the irregular ground where the corestones were come out will show clear geotechnical differences between the ground and the gradually weathered bedrock, nowadays, the construction sites do not take into account the characteristic of core-stone region. In conclusion, to study the failure-strength characteristics of soil layers containing core-stones, we made artificial core-stones and varied percentage of corestones, and measured cohesion and friction factors to adjust them to construction sites containing corestones such as slope, tunnel, and underground.

• Proceedings of the Korean Geotechical Society Conference
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• 1998.10a
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• pp.65-72
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• 1998