• 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.

• Geotechnical Engineering
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• v.13 no.4
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• pp.13-24
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• 1997

A predicting method for ultimate vertical and horizontal bearing capacity by means of PAR(Pile Analysis Routines) was suggested. Based on the static pile load test data, case studies by means of PAR were performed. Ultimate pile capacity predicted by PAR was within 15% error range of that determined by stairs pile load tests. Also, the results of static pile load test, statnamic tests and PDA data performed on pipe piles were compared and, by using PAR, ultimate pile capacity was determined. Distributions of atrial pile load could be predicted and load transfer analysis could be done approximately by those distributions.

• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.5-15
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• 2004

SIP has been widely used as a low noise and vibration piling method in Korea. But the quality control of SIP was not properly settled down and field workers did not fully understand the principle of SIP method. So not a less troubles were raised at construction site and bearing capacity was not fully mobilized. To settle these problems, Korea National Housing Corporation amended the construction and load test criteria of SIP in 2002. After load tests on the SIPs installed in field according to the new criteria, we found that the bearing capacity in field vs the design load ratio increased and bearing characteristics was enhanced than that installed by the former criteria. To consider the enhanced bearing characteristics in the pile design and determine the adequate design criteria, this paper analyzed the accuracy of design criterion which were commonly used in Korea comparing with the load test results. Analysis result shows that Meyerhof criteria(1976) properly simulates the bearing capacity of SIP installed by the new construction and load test criteria.

• Journal of the Korean Geotechnical Society
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• v.35 no.8
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• pp.31-42
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• 2019

A total of 73 pile design data for prebored PHC piles was analyzed to study the current design method. Based on the design data, a ratio of skin friction to total capacity from the pile design data was about 20~53%. Such low ratio of skin friction to total capacity tends to underestimate skin friction. Considering this tendency, the current design method should be improved. Also, an average design efficiency of PHC pile capacity was 70% and an average design efficiency for bearing capacity of soil or weathered rock was 80%, which shows slightly higher value than the former. This is probably due to the fact that the allowable bearing capacity is estimated to be equal to or slightly higher than the design load. Hence, the allowable bearing capacity should be estimated to be higher than the long-term allowable compressive force of the PHC pile. In the current design method, skin friction is calculated to be about 2.2 times lower than end bearing. The current design method for prebored PHC piles applied foreign design methods without any verification of applicability to the domestic soil or rock condition. Therefore, the current design method for prebored PHC piles should be improved.

• Journal of the Korean GEO-environmental Society
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• v.13 no.10
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• pp.33-42
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• 2012

The efficiency of the current design methods for computing pile resistances is analyzed using field load-settlement tests results. Twelve load-settlement test data for drilled shafts and bored piles were obtained from the literature. These load-test data were fitted using the t-z method. Subsequently, the ultimate resistances were evaluated based upon the failure criteria from following methods: (1) the Davisson's approach and (2) settlement corresponding to 5% or 10% shaft diameter approach. The ultimate resistances for these drilled shafts and bored piles were also predicted using methods based on the design code from North America (United States, Canada), Europe, and Asia (Japan). The pile resistances determined from field load-settlement tests were compared with those calculated using the design codes. The comparisons show that most design codes predict a conservative resistance for drilled shafts and bored piles. However, in the case of drilled shafts, we find that some of the design codes can over-predict the resistance and, therefore, should be applied cautiously. This research also shows that the t-z method can be successfully used to predict the ultimate resistance and the load transfer mechanism for a single pile.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.713-720
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• 2008

본 연구는 낙동강 하구 대심도 연약지반에 항타관입된 PHC 말뚝에 대하여 SPT 지지력 공식으로 부터 계산된 선단지지력 값과 PDA 시험에서 얻어진 선단지지력 측정값을 비교하였다. 또한, SPT N값이 50이 넘는 경우에 대하여는 N값과 롯드 관입깊이의 선형관계를 가정하여 30cm 관입깊이에 해당하는 N값을 적용한 경우와 CPT $q_c$와의 상관성을 이용하여 $q_c$값으로부터 N값을 산정한 경우의 2가지 분석을 수행하였다. 그 결과, 본 연구에서 적용한 SPT 지지력 공식 모두 측정된 선단지지력 값과 차이가 났으며, SPT 지지력 공식은 대심도 연약지반에 항타 근입된 말뚝에 대하여 실제적인 설계를 수행할 때 신뢰하기 어려운 것으로 나타났다. 또한, N>50인 경우에 대하여 N값과 롯드 관입깊이의 선형관계를 적용하는 것은 지지력을 매우 과대평가하는 것으로 나타났다.

• Geotechnical Engineering
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• v.14 no.5
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• pp.163-172
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• 1998

To study the carrying capacity behavior of pile, dynamic pile testis and static load tests were carried out on two instrumented piles during and some time after pile driving. Cone Penetration Test( CPT) and Standard Penetration Test(SPT) were also performed at the test site before pile tests to investigate the relationship between unit skin friction of piles and cone tip resistance values and SPT N values. Total static capacity of pile reached the ultimate stage at the pile head settlement of about 0.055D (D : Pile diameter), at which skin friction of Pile already Passed the maximum value, but the end bearing was still increasing with the pile head settlement. The carrying capacity of pile increased in the form of natural logarithmic function with the time after pile driving. The increase in skin friction with time was very substantial the increase in skin friction 40 days after pile driving was 4.6 times of that determined during pile driving. The contribution of skin friction to the total capacity twas insignificant in the beginning, but became substantial 40 days after pile driving. This implies that the tested pile initially responded as an end bearing pile and later behaved as a friction pile. It was also noted that unit skin friction of pile might be ielated to cone tip resistance values(q.) and SPT N values, though the coefficient of this relationship might differ from one soil group to another and was somewhat greater than the value used in the design practice of Korea.

• Journal of the Korean GEO-environmental Society
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• v.5 no.2
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• pp.51-62
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• 2004

Granular compaction piles have the load bearing capacity of the soft ground increase and have the settlement of foundation built on the reinforced soil reduce. The granular compaction group piles also have the consolidation of the soft ground accelerate and have the liquefaction caused by earthquake prevent using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful methods in Korea. The Granular compaction piles are constructed by grouping it with a raft system. The confining pressure at the center of bulging failure depth is a major variable in relation to estimate for the ultimate bearing capacity of the granular compaction piles. Therefore, a share of loading is determined considering the effect of load concentration ratio between the granular compaction piles and surrounding soils, and varies the magnitude of the confining pressure. In this study, method for the determination of the ultimate bearing capacity is proposed to apply a change of the horizontal pressure considering bulging failure depth, surcharge and loaded area. Also, the ultimate bearing capacity of the granular compaction piles is evaluated on the basis of previous study on the estimation of the ultimate bearing capacity and compared with the results obtained from laboratory scale model tests. And using the result from laboratory model tests, it is studied increase effect of the bearing capacity on the granular compaction piles and variance of coefficient of consolidation for the ground.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.07a
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• pp.65-91
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• 1999

말뚝기초의 지지력예측방법 중 신뢰도가 가장 높은 것은 말뚝정재하 시험방법이므로 말뚝기초의 경제적이고 신뢰성있는 설계를 위하여 하중전이의 측정이 수반된 말뚝재하시험을 실시하여야 할 것이다. 따라서, 말뚝재하시험 방법들에 대하여 고찰하고, 시험결과의 해석사례를 설명하였다. 또한, 신뢰성있는 말뚝재하시험 수행을 위하여 고려해야 할 점들도 설명하였다. 또한, 하중전이측정실험에 대한 기본개념을 고찰하였으며, 이 결과의 활용방안에 대한 설명도 부가하였다.