• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.17-30
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• 2004

In this study, a new formula of settlement at the head of IGM was suggested and the applicability of suggested formula was verified with field test results. This suggested formula was the function of the settlement at the shaft head and the elastic compression of shaft. The applicability of suggested formula was verified with the result of in-situ load test. Also, the bearing capacity of drilled shaft with the IGM's theory was compared with those of classical theories. The results showed that classical method showed smaller values of bearing capacity than those of field load test data. The results of analysis also showed that the suggested formula and IGM's theory were applicable for the estimation of bearing capacity with the increase of shaft settlement. Especially, settlement correction factor($k_m$), which reflects ground condition and load transfer characteristics, increases as the applying load and shaft deformation increase. This suggested formula was applicable for medium density or higher density of soil condition and $k_m=1$ means yielding load for firm soil condition.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.241-250
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• 2011

The design method of IGM proposed by FHWA to predict bearing capacities of drilled shaft socketed in weathered granite has been used generally. In this study, site investigations were performed in a pilot test site, and disturbance and roughness were measured. Geotechnical properties were assorted as cohesive material and undisturbed and smooth surface. A simple relationship was proposed to predict unconfined strength ($q_u$) of weathered granite using static load test results, load transfer test results and N values. It was confirmed that the design method to estimate bearing capacities of drilled shaft could improve IGM's theory for weathered granite from this research.

• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.379-385
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• 2013

In this study, partial drilled shafts (Bottom Cast-in-place Concrete pile) were applied to the pilot test site to ensure the bearing capacity; we used the skin friction force in the IGM to analyze the feasibility of the application of IGM theory. The soil characteristics were analyzed in cohesive, non-smear, and smooth conditions for the application of the IGM theory via geotechnical investigation and measurement of the disturbance and surface roughness. Static load and load transfer tests were conducted to calculate the allowable bearing capacity and the skin friction force by depth. The skin friction force increased with increase in the depth and standard settlement, showing a very high correlation. In addition, because the unconfined strength ($q_u$), which is the most important parameter in the cohesive IGM, cannot be measured in a weathered granite area, the static load and load transfer test results and the N value were used to obtain $q_u$.

• Journal of the Korean GEO-environmental Society
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• v.7 no.1
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• pp.19-28
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• 2006

In Korea, none of the design methods, which can consider the properties of hard soil, weathered rock and the condition of construction, are suggested. Therefore, the properties of geomaterial are simply classified into three categories such as sand, clay and rock for the resistance estimation of axially loaded drilled shafts in Korea. However, in America, O'Neill et al.(1996) presented design methods for a new category of geomaterial which is between soil and rock termed "intermediate geomaterials, IGM's". And FHWA(1999) adapted above most complete classification of geomaterials in its design manual. However, in Korea, these properties are depended on the engineer's judgement, the weathered rocks may be counted as soils, although they may be referred to as IGM's in America. In this study, the applicability of IGM method was investigated through the three construction sites in Korea. For the comparison, two geomaterial properties are applied, respectively. The one was sound soil condition and the other was IGM condition and classical design method and IGM method were applied, respectively. The results showed that the predicted bearing capacities of drilled shafts with IGM's were larger than the predicted values by the classical design method with sound soil condition.

• Journal of the Korean GEO-environmental Society
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• v.6 no.2
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• pp.61-73
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• 2005

In Korea, none of the design methods, which can consider the properties of hard soil, weathered rock and the condition of construction, are suggested. Therefore, the properties of geomaterial are simply classified into three categories such as sand, clay and rock for the resistance estimation of axially loaded drilled shafts in Korea. However, in America, O'Neill et al.(1996) presented design methods for a new category of geomaterial which is between soil and rock termed "intermediate geomaterials, IGM's". And FHWA(1999) adapted above most complete classification of geomaterials in its design manual. However, in Korea, these properties are depended on the engineer's judgement, the weathered rocks may be counted as soils, although they may be referred to as IGM's in America. In this study, the applicability of IGM method was investigated through the two construction sites in Korea. For the comparison, two geomaterial properties are applied, respectively. The one was sound soil condition and the other was IGM condition and classical design method and IGM method were applied, respectively. The results showed that the predicted bearing capacities of drilled shafts with IGM's were larger than the predicted values by the classical design method with sound soil condition.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.29-40
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• 2004

The bearing capacity of drilled shaft is affected by several factors, such as shaft length, shape, surface roughness, young's modulus of geomaterials and shaft, soil strength, confining stress and so on. However, there has been no design method of drilled shaft considering all factors mentioned above. Moreover, since geomaterials are simply classified as sand, clay and rock, there was no design criterion for IGM (Intermediate Geomaterials). Therefore, the rigorous design approach of drilled shaft was not possible by classical design method. However, since these characteristics were not considered in classical theories, bearing capacity was generally different ken practical value. In this study, the bearing capacity of drilled shaft with the IGM's theory was compared with those of classical theories. The results showed that classical method showed smaller values of bearing capacity than those of field load transfer data. Moreover, the evaluated value of bearing capacity with IGM theory corresponded fairly well with those of field data.