• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1290-1295
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• 2008

The relative density of soil indicate loose and dense state of sand. Because sand is low compressibility, initial relative density of sand is important effect factor of compression and shear behavior. To measure exactly relative density, the exactly maximum and minimum void ratio was determinated by laboratory tests. Generally, vibrating table method is adapted for minimum void ratio(KS F 2345). However KS F 2345 is not consider the particle break during the vibrating table test. In this study, The minimum void ratio is compared with a method of Pluviation and Vibrating table test results using the K-7(crushed sand). It is concluded that the K-7 sand particles were crushed during the vibrating table test and vibrating table test is not a suitable test for a crushed sand $e_{min}$.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.117-125
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• 2008

The detection of thin-layered soil is important in soft soils to evaluate the soil behavior. The smaller diameter cone penetrometer have been commonly used to detect the layer with increasing sensitivity. The objective of this study is to detect the thin-layered soil using cone resistance and electrical resistance. The cone resistivity penetration test (CRPT) is developed to evaluate the cone tip resistance and electrical resistance at the tip. The CRPT is a micro-cone which has a $0.78cm^2$ in projected area. The application test is conducted in a laboratory large-scale consolidometer (calibration chamber). The kaolinite, sand and water are mixed to make the specimen at the liquid limit of 46% using a slurry mixer. It takes two months for the consolidation of the specimen. After consolidation, the CRPT test is carried out. Furthermore the standard CPT results are compared with the electrical resistance measured at the tip in the field. This study suggests that the CRPT may be a useful tool for detecting thin-layers in soft soils.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1251-1258
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• 2008

The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.944-955
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• 2009

In this thesis the model tests were performed to the pull-out characteristics of a suction pile subjected to a pull-out in sands. For this model tests, three different soil conditions ($D_r$=45, 65, 82%), three pile diameters (D=100, 150, 200mm) and three pile lengths (L=100, 150, 200mm), were changed. And the experimental results were also compared with those by the theoretical methods. The results by the experimental and theoretical analysis are as follows. The ultimate pull-out resistances increased as the relative density of sands, pile diameter, length and the ratio of pile length to diameter increased. The ultimate pull-out resistance by Meyerhof method(1973) overestimated that by the model test, but the results using the soil-pile friction angle suggested by Aas(1966) in the Meyerhof(1973) method were in good agreement with the experimental results.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1214-1223
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• 2009

In this study, a composite behavior of stone columns reinforced in soft ground, Sabkha, have been evaluated by a series of field measurements and numerical analysis. Field loading tests were performed to verify the effect of the composite ground reinforced by stone columns in Kayan, Saudi. The settlement measured in the field test was compared with the settlement calculated by the Priebe method and the numerical analysis using ABAQUS. It is found that the settlement estimated using the Priebe method significantly overestimated the settlement measured in the field test. In addition, it is confirmed that consideration of confinement effect exerted by surrounding stone columns in a numerical simulation is indispensable to estimate the settlement of composite ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1441-1446
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• 2009

Numerical analysis is a powerful method in evaluating the soil-pile-structure interaction under the dynamic loading, and this approach has been applied to the practical area due to the development of computer technology. Finite Difference Method, one of the most popular numerical methods, is sensitive to the shape and the number of mesh. However, the trial and error approach is conducted to obtain the accurate results and the reasonable simulation time because of the lack of researches about mesh size and the number. In this study, FLAC 3D v3.1 program(FDM) is used to simulate the dynamic pile model tests, and the numerical results are compared with the 1G shaking table tests results. With the different size and shape of mesh, the responses of pile behavior and the simulation time are estimated, and the optimum mesh sizes in dynamic analysis of single pile is studied.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1383-1390
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• 2009

This study conducted a series of drained triaxial test in order to determine the critical state parameters of a high compressible Jeju sand. Jeju sand is classified into mixed sand containing both siliceous and calcareous materials and has high extreme void ratios due to the angularity of grains and the intra-particle voids of hollow particles. It is observed that the behavior of Jeju sand is similar to that of general calcareous sand. The friction angle of Jeju sand at critical state gradually decreases with increasing the mean effective stress. Test result shows that the particle crushing resulted from stress during shear causes the reduction of void ratio at critical state.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1025-1028
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• 2009

Earth and rock fill dam is our typical dam because of their inherent flexibility and adaptability to various fundation conditions. In order to secure structural safety, rockfill materials are used angular particles obtained by blasting parent rock or rounded particles collected from river beds. Concrete-faces rockfill dams(CFRD) and Concrete-faces gravelfill dams(CFGD) have become popular in the last 20 years as s result of their good performance and low cost compared with the rockfill dam. These Dams are also constructed by the materials. A key factor in the design of the dams is the deformations induced during construction and upon reservoir filling. These can be predicted using the stress-strain and strength properties can be adequately define. However the stress-strain properties of rockfill are difficult to determine because the properties are affected by such factors as particle grading, size and shape of particles, stress conditions, and particle crushing. In our study, testing of the behavior of the rockfill materials are essential prerequisites to the realistic analysis and design of the CFGD. This paper deals with laboratory testing of particle crushing among the study.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.913-922
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• 2009

Fourteen model pile load tests using a calibration chamber and instrumented model pile were preformed to investigate the variation of the behaviors of driven piles in sands with soil and lateral cyclic loading conditions. Results of the model tests showed that the first loading cycle generated more than 70% of the pile head rotation developed for 50 lateral loading cycles. Lateral cyclic loading also made an increase of the ultimate lateral load capacity of piles for $K_0$=0.4 and an decrease for $K_0$ higher than 0.4. Higher portion of the increase or decrease in the ultimate lateral load capacity by lateral cyclic loading was generated for the first loading cycle due to densification of loosening of the soil around the pile by lateral cyclic loading. It was also observed that a two-way cyclic loading caused higher ultimate lateral load capacity of driven piles than a one-way cyclic loading. When the pile was in the ultimate state, the maximum bending moment developed in the pile increased with increasing $K_0$ value of soil and was insensitive to the magnitude and number of lateral cyclic loading.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.173-186
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• 2015

The rapid urbanization in Pakistan is creating a shortage of sustainable construction sites with good soil conditions. Attempts have been made to use rice husk ash (RHA) in concrete industry of Pakistan, however, limited literature is available on its potential to improve local soils. This paper presents an experimental study on engineering properties of low and high plastic cohesive soils blended with 0-20% RHA by dry weight of soil. The decrease in plasticity index and shrinkage ratio indicates a reduction in swell potential of RHA treated cohesive soils which is beneficial for problems related to placing pavements and footings on such soils. It is also observed that the increased formation of pozzolanic products within the pore spaces of soil from physicochemical changes transforms RHA treated soils to a compact mass which decreases both total settlement and rate of settlement. A notable increase in friction angle with increase in RHA up to 16% was also observed in direct shear tests. It is concluded that RHA treatment is a cost-effective and sustainable alternate to deal with problematic local cohesive soils in agro-based developing countries like Pakistan.