• Title/Summary/Keyword: Unit skin friction

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A Comparison of Roughness Measurement and Load Transfer Test for the Calculation of Unit Skin Friction of Pile Foundation in Soft Rocks (기초 연암부 벽면거칠기 시험과 하중전이 시험 결과의 비교 및 단위주면마찰력의 산정에 대한 연구)

  • Hong, Seok-Woo;Hwang, Geun-Bae
    • Journal of the Korean Geotechnical Society
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    • v.39 no.6
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    • pp.21-30
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    • 2023
  • One of the methods for calculating unit skin friction of soft-rock-socket parts for cast-in-place piles involves the roughness measurement of the parts. The measurements are conducted during the excavation stage. A roughness measuring device is installed in the excavation hole and the unit skin friction is calculated from the measured surface roughness of the rock socket. Herein, the results of roughness measurement of rock-socket parts in cast-in-place piles and that of load transfer tests are analyzed and compared. The unit skin friction from the roughness measurements can be converted into unit skin friction corresponding to the displacement of a pile generated in a load transfer test. A reduction factor is given as Rf = -0.14n + 1.48.

A Study on Characteristics of the Unit Skin Friction Using the Wall Roughness in the Soft Rock (연암부 벽면거칠기를 이용한 단위주면마찰력 특성에 관한 연구)

  • Hong, Seok-Woo;Hwang, Geun-Bae
    • Journal of the Korean Geotechnical Society
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    • v.35 no.12
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    • pp.7-13
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    • 2019
  • In the case of the drilled shaft, one of the methods for calculating unit skin friction stress of rock socket parts is to measure the roughness of the excavated face. This method is to estimate the unit skin frictional resistance using a device which measures the roughness shape of the excavated face in the excavation step. In this study, the roughness shapes of the face of the rock socket part in the drilled shaft were measured directly in the perforated hole and the results are used to identify the characteristics of the unit skin friction of the bedrock. In addition, the static load test and the load transfer test were performed on the same pile to verify the result of the roughness test.

A Study on the Skin Friction Characteristics of SIP and Numerical Model of the Interface Between SIP and Soils (SIP말뚝의 주면마찰특성 및 주면 경계요소의 수치모델에 관한 연구)

  • 천병식;임해식
    • Journal of the Korean Geotechnical Society
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    • v.19 no.2
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    • pp.247-254
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    • 2003
  • While the interests in the environmental problem during the construction are increasing, the use of low noise-vibration auger-drilled pilling is increasing to solve noise and vibration problem in pilling. Therefore, in Korea, SIP (Soil-Cement Injected Precast Pile) method is mainly used as auger-drilled pilling. However, there is no proper design criteria compatible with the ground condition of Korea, so which is most wanted. To improve and supplement this situation, direct shear tests for the friction between SIP pile skin interface and soil were executed on various conditions. Through the analysis of test results, skin friction characteristics of SIP were investigated thoroughly Also, hyperbolic model parameter fomulas which describe the friction behavior and the new non-linear unit skin friction capacity model with SM, SC soil were suggested.

A Study on the Development of Design Chart for Drilled Shaft Socketed into Weathered Zone Using DCPT (Driving Cone Penetrometer Test) (DCPT를 이용한 풍화대 소켓 현장타설말뚝의 설계도표 개발에 관한 연구)

  • Jung, Sung-Min;Kwon, Oh-Sung;Lee, Jong-Sung;Lee, Min-Hee;Choi, Yong-Kyu
    • Journal of the Korean Geotechnical Society
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    • v.26 no.5
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    • pp.5-13
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    • 2010
  • For the development of design chart for drilled shafts socketed into weathered zone, the 6 bi-directional pile load tests with load transfer measurements done in two in-situ sites were performed. Also, DCPTs were performed in each test point. Maximum unit skin frictions and maximum unit end bearing capacities from pile load test results were analyzed. Inter-relationships between DCPT's characteristics were also analyzed. In the soils, the inter-relationships of maximum unit skin friction and DCPT appeared so low. But in the weathered zones, inter-relationships between maximum unit skin friction / maximum unit end bearing capacity and DCPT were so high that the coefficient of correlation is over 0.70.

Bearing Capacity of In-situ Cast Piles in Weak Sedimentary Rocks (미고결 퇴적암층에서의 현장타설말뚝 지지력 특성 연구)

  • Sim, Dong-Hyun;Kim, Ki-Seop;Yu, Seok-Joon
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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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.

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Pile Load test on a Large Barrette Pile and a Bored Pile for the Identification of the Load Transfer Characteristics (대형 바렛말뚝과 현장타설말뚝의 하중전이특성 파악을 위한 재하시험)

  • Han Sung-Gil;Park Jong-Kwan
    • Journal of the Korean Society for Railway
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    • v.9 no.4 s.35
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    • pp.493-498
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    • 2006
  • In this study, two large pile load tests were performed in the deep sand gravel deposit of Nakdong river basin so that the characteristics of the load transfer was identified. The fully instrumented rectangular barrette pile in the size of $1.5\times3.0m$ and the circular bored pile of the diameter 1.5 m were placed into the ground below 50 m. Under the applied loads of 2,400 tonf and 4,000 tonf, the test results of the load transfer showed the portion of 83% and 93% of the applied loads on the barrette pile and the bored pile, respectively, were supported by the skin friction along the pile shaft. It was revealed that the most of these skin friction mobilized in sand layer underlying clay layer having N-value more than 30 and that the friction per unit area of the bored pile was larger than the friction of barrette pile. However, if embedded in the stiff sand graval layer, the both piles were proven to be sufficient for using as the friction piles.

A Field Test Study on Skin Friction Behavior of Driven Steel Piles (항타강관말뚝의 주면마찰저항 특성에 관한 현장실험 연구)

  • Lee, Min-Hee;Lee, Chung-Sook;Jung, Chang-Kyu;Choi, Yong-Kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.575-582
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    • 2005
  • Static pile load tests for three instrumented driven steel pipe pies were performed. Based on the distributions of pile axial loads along the pile depth, Characteristics of unit skin friction were analyzed.

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Carrying Capacity Behavior of Instrumented PC Piles (시험 콘크리트 말뚝의 지지력 거동)

  • 이영남;이종섭
    • 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.

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Skin Friction Mobilized on Pack Micropiles Subjected to Uplift Force (인발력을 받는 팩마이크로파일의 주면마찰력)

  • Hong, Won-Pyo;Cho, Sam-Deok;Choi, Chang-Ho;Lee, Choong-Min
    • Journal of the Korean Geotechnical Society
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    • v.28 no.6
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    • pp.19-29
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    • 2012
  • Pack micropiles were recently developed to improve pile capacity of general micropiles. Pack micropiles were made by warping thread bar or steel pipe of general micropile by geotexlile pack and grouting inside the pack with pressure. According to the pressure, the boring hole could be enlarged. A series of pile uplift tests were performed on three micropiles. Two out of the three piles were the pack micropiles and the other was the general micropile, in which a thread bar was used in the boring hole. According to the pressure applied to the pack micropiles, the diameter of boring hole was enlarged from 152 mm to 220 mm. Unit skin friction mobilized on side surfaces of micropiles increased with displacement of pile head and reached on a constant value, which represents that the relative displacement between piles (or thread bar) and soils was reached on critical state. And the uplift resistance of pack micropile was higher than that of general micropile. Two reasons can be considered: One is that the frictional surface increases due to enlarging diameter of boring holes and the other is that the unit skin friction could increase due to compressing effect of surrounding soils by soil displacement as much as the enlarging volume of boring hole. The compression effect appeared at deeper layer rather than surface layer. The unit skin friction mobilized on micropiles with small diameter was higher than the ones on large bored piles.