• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.100-109
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• 2004

Is this study, results of static pile load tests of in-situ cast piles in weak or uncemented sedimentary rock layers have been analyzed and presented. Consdierations on the characteristics of soils sedimentary rocks have been made. From the measurements of strain gauges and extensometers the relationship of unit skim friction versus displacement and that of unit end bearing versus displacement have been obatined to verity the characteristics of bearing capacity of this uncemented sedimentary rock layers. Also, a comparison has been made between ultimate skin friction in compression and tension.

• 한국지반공학회논문집
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• 제29권7호
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• pp.17-36
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• 2013

본 연구에서는 해상 교량 현장과 초고층빌딩 현장에서 실시한 암반에 근입된 대구경 현장타설말뚝의 양방향 재하시험(총 4개 현장, 13개 말뚝) 결과를 분석하여 연암에서의 주면마찰력과 선단지지력 산정을 위한 경험식을 제안하였다. 양방향 재하시험을 위하여 각 시험 말뚝의 정 중앙 위치에서 시추 및 지반조사가 이루어졌으며, 각 말뚝에 부착한 계측장치로부터 얻은 데이터를 이용하여 주면의 f-w 곡선과 선단의 q-w 곡선을 작성하였다. 이 곡선들로부터 - 지반조사결과들과 주면마찰력 및 선단지지력에 대한 다중회귀분석을 실시하여 - 변위에 따른 극한 주면마찰력과 선단지지력 산정식을 제안하였으며, 이 결과를 기존의 경험식들과 비교 분석하였다. 변위가 증가할수록 지지력이 증가하는 국내 암반의 f-w 곡선과 q-w 곡선의 특성상, 다양한 말뚝 변위기준에 따라 제안한 경험식들이 변위와 무관하게 일정한 극한값으로 제안된 기존의 경험식들보다 더 합리적인 것으로 판단된다. 본 연구의 제안식들 중에서 일축압축강도의 함수로 나타낸 주면마찰력 및 선단지지력에 대한 제안식이 다른 지반정수들에 의한 경험식보다 좋은 상관관계를 보여주는 것으로 나타났다.

• 한국건축시공학회지
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• 제12권5호
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• pp.510-517
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• 2012

This study evaluated the recycling potential of in-site waste soil as pile back filling material (PBFM). We performed experiments to check workability, segregation resistance, bond strength, direct shear stress test, and dynamic load test using in-site waste soil in coastal areas. We found that PBFM showed better performance than general cement paste in terms of workability, segregation resistance, and bond strength. On the other hand, the structural performance of PBFM was slightly lower than that of general cement paste due to the skin friction force of pile by Pile Driving Analyzer and direct shear stress. However, because this type of performance degradation in terms of structure can be improved through the use of piles with larger diameter or by changing the type of pile, considering the economics and environment, we considered that recycling of PBFM has sufficient value.

• Geomechanics and Engineering
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• 제23권6호
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• pp.513-521
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• 2020

In this paper, due to the need for cutting cement-soil group pile composite foundation under the 7-story masonry structure of Zhenghe District and the shield tunnel of Zhengzhou Metro Line 5, a field test was conducted to directly cut cement-soil single pile composite foundation with diameter Ф=500 mm. Research results showed that the load transfer mechanism of composite foundation was not changed before and after shield tunnel cut the pile, and pile body and the soil between piles was still responsible for overburden load. The construction disturbance of shield cutting pile is a complicated mechanical process. The load carried by the original pile body was affected by the disturbance effect of pile cutting construction. Also, the fraction of the load carried by the original pile body was transferred to the soil between the piles and therefore, the bearing capacity of composite foundation was not decreased. Only the fractions of the load carried by pile and the soil between piles were distributed. On-site monitoring results showed that the settlement of pressure-bearing plates produced during shield cutting stage accounted for about 7% of total settlement. After the completion of pile cutting, the settlements of bearing plates generated by shield machine during residual pile composite foundation stage and shield machine tail were far away from residual pile composite foundation stage which accounted for about 15% and 74% of total settlement, respectively. In order to reduce the impact of shield cutting pile construction on the settlement of upper composite foundation, it was recommended to take measures such as optimization of shield construction parameters, radial grouting reinforcement and "clay shock" grouting within the disturbance range of shield cutting pile construction. Before pile cutting, the pile-soil stress ratio n of composite foundation was 2.437. After the shield cut pile is completed, the soil around the lining structure is gradually consolidated and reshaped, and residual pile composite foundation reaches a new state of force balance. This was because the condensation of grouting layer could increase the resistance of remaining pile end and friction resistance of the side of the pile.

• Geomechanics and Engineering
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• 제5권2호
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• pp.119-142
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• 2013

Pile load tests using Osterberg cells (O-cell) were conducted on cast-in-place concrete piles founded in oil sand fill and in situ oil sand at an industrial plant site in Fort McMurray, Alberta, Canada. Interpreted pile test results show that very high pile shaft resistance (with the Bjerrum-Burland or Beta coefficient of 2.5-4.5) against oil sand could be mobilized at small relative displacements of 2-3% of shaft diameter. Finite element simulations based on linear elastic and elasto-plastic models for oil sand materials were used to analyze the pile load test measurements. Two constitutive models yield comparable top-down load versus pile head displacement curves, but very different behaviour in mobilization of pile shaft and end bearing resistances. The elasto-plastic model produces more consistent matching in both pile shaft and end bearing resistances whereas the linear elastic under- and over-predicts the shaft and end bearing resistances, respectively. The mobilization of high shaft resistance in oil sand under pile load is attributed to the very dense and interlocked structure of oil sand which results in high matrix stiffness, high friction angle, and high shear dilation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 말뚝기초 학술발표회
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• pp.65-84
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• 2000

Europe and US which have more restrictive regulations than Korea about the noise and vibration during construction are using Auger-cast Pile to reduce the problem relating with noise and vibration. However Auger-cast Pile has problems like difficult quality control and low bearing capacity. In Europe, Displacement in-situ concrete Pile has been used to sove that problems since 1990s, and Korea has performed the test construction in 1997 and it has been used as the real structural foundation since 1998. Test and real construction results verified that the allowable capacity of the pile(diameter = 410mm) is between 70 and 100ton. Though De Beer & Van Imps design method utilizing CPT result is used to calculate the bearing capacity of the Displacement in-situ Pile, Korea is dependant upon the SPT as the sounding test, so design method utilizing SPT result is necessary to promote the application of the pile. To find out reasonable design method using SPT result, rearing capacity of the pile constructed in sand and clay in Korea was calculated using Meyerhof, SPT-CPT translation method, Nordlund, Douglas and DM-7 method, and the calculation results were compared to the load test result. Analysis result shows that SPT-CPT translation method is more reliable than others and economical design can be possible because it considers efficiently the friction capacity of Displacement in-situ Pile.

• 한국지반공학회논문집
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• 제36권11호
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• pp.107-117
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• 2020

개단 강관말뚝의 경우 일반적으로 말뚝에 작용하는 외부 주면 마찰력뿐만 아니라 설치과정에서 폐색된 흙이 강관 내부에 작용하는 내부 마찰저항이 존재한다. 내·외부 저항에 따라 극한하중의 변화가 예상되며, 말뚝이 시공된 지반이 점성토일 경우 지반 침하로 유발되는 부주면 마찰력에도 영향을 끼칠 것으로 판단된다. 따라서 본 연구에서는 강관말뚝 내·외부 저항 특성에 따른 거동을 수치해석적으로 분석하고자 하며, 지반 침하 발생 전·후의 마찰력 분포, 축력, 침하량을 산정하였다. 해석 결과, 내부 마찰 저항은 외부 마찰 저항보다 적은 영향을 미쳤지만 전체적인 말뚝 거동에 끼치는 영향을 고려하였을 때, 중요한 요소 중 하나이며 설계 시 두 가지 저항요소를 고려할 필요가 있을 것으로 판단된다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.87-93
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• 1994

Factors which affect the capacity and the soil plug condition of an open-ended pile can be broadly divided into three categories:i.e., pile conditions, soil conditions and penetration methods. It has been found that the relative density and the horizontal stress have much effects on the soil plug behavior than other soil conditions. Also, it has been found that the pile diameter is the most important factor among pile conditions. However, a few investigations have been performed to account for both soil conditions and pile conditions. In this paper, a number of calibration chamber tests have been conducted with three different sized open-ended model piles. The model pile was driven into siliceous sand, with varying soil conditions, to clarify coupled effects of pile diameter and soil conditions on the plug behavior, the capacity, and the load trasfer mechanixm of soil plug. The model piles are composed of two stainless steel pipes so as to measure the plug capacity, the tip resistance, and the outside skin friction. separately.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1287-1294
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• 2006

A pile is compressed with settlements when loading and bearing capacity is altered along relative displacement of pile/soil on settlement and compression. Settlements of pile displaying limit skin friction is different from displaying tip resistance. Therefore, it is an error in traditional method that bearing capacity of pile is estimated from the sum of limit skin fraction and tip resistance. Accordingly, development of design method considering behavior of load-settlement is needed. In this study, we would like to establish the base for development of design method considering bearing capacity altering along displacement on settlement and compression. For this, we established system and substance of design method. And in order to establish relationship of load-settlement of pile on the type of soil, we analyzed and arranged existing database and pile loading test. On design method, settlement is assumed gradually on each capacity level being assumed gradually. Bearing capacity developing on the pile is obtained on each settlement level. Until the obtained bearing capacity will be equal to assumed capacity, this process is continued with increasing settlement. Load-settlement curve for soil classification is sketched in the process computing settlement on assumed capacity. This design method will be materialized by computation program.

• 한국지반공학회지:지반
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• 제11권4호
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• pp.75-86
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• 1995

내관과 외관으로 구성된 모형 개단 말뚝을 압력 토조속에 상이한 설치방법으로 관입한 후,실제 지진 기록을 이용하여 모델링시킨 유사 지진을 작용시켜 개단 말뚝에서의 지지력 저감 특성을 고찰하였다. 유사 지진 진동에 의한 극한 지지력 감소율은, 타격 관입 말뚝에서 약 20%였으며, 진동 관입 말뚝의 경우 약 40%에 달하였다. 또한,외주변 마찰력의 감소는 극한 지지력 감소의 대부분을 차지하여 약 80%였으며, 선단 강재부 지지력과 관내토 폐색력은 각각 약 10%였으며, 이러한 경향은 말뚝의 설치방법에 따라 크게 달라지지 않았다.