• Title, Summary, Keyword: 군말뚝

Search Result 65, Processing Time 0.042 seconds

Estimation of Lateral Dynamic P-multiplier of Group Pile Using Dynamic Numerical Analysis Results (동적 수치해석 결과를 이용한 군말뚝의 횡방향 동적 P-승수 산정)

  • Park, Jeong-Sik;Jeong, Sang-Seom
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.38 no.4
    • /
    • pp.567-578
    • /
    • 2018
  • In this study, to investigate the effect of the stress reduction of group piles by dynamic loading, a dynamic p-y curve was established and the dynamic p-multiplier was calculated. Dynamic numerical analysis was performed by input sinusoidal waves to the bottom of the pile - ground system for $2{\times}2$ group pile, single pile and $5{\times}5$ group pile, single pile in dry sandy soil, and the pile spacing was changed to 2.5 and 5.0 times of the pile diameter. By establishing and comparing the dynamic p-y curves of the single pile and group piles, the dynamic group pile effect of the piles according to the pile center spacing and row position of the group pile piles is analyzed. $5{\times}5$ showed symmetry of the dynamic P-multiplier value around the pile origin coordinate. The dynamic p-multiplier value at the single pile, $5{\times}5$ pile (pile spacing: 2.5D) is 0.26 ~ 0.30 at the pile number 3, pile number 23, 0.14 pile number 13, and 0.14 ~ 0.38 at the pile number 5, pile number 18. These values differed from the static p-multiplier, especially due to the different loading conditions. The dynamic p-multiplier ($P_{dm}$) estimation through various types of input dynamic loads is expected to be used for dynamic design and analysis of group pile-ground systems of civil foundation structures.

An Experimental Study on Local Scour Around Group Pile Foundation (군말뚝 주변의 국부세굴에 관한 연구)

  • Yun, Byeong-Man;Seo, Jeong-Pil;No, Yeong-Sin
    • Journal of Korea Water Resources Association
    • /
    • v.34 no.6
    • /
    • pp.641-649
    • /
    • 2001
  • This study analyzed the general scour characteristics around group pile foundations through laboratory experiments. The experiments were performed for the pile groups consisting of 4, 9, 15 and 35 piles to investigate the effects of pile number, mean velocity and the angle of attack on the scour hole shape, and the magnitude and the position of maximum scour depth. Results reveal that the maximum scour depth for 4 and 9 piles have almost same values with single pier case regardless of approach velocity. The scour depth for 15 and 35 piles, however, increases as the mean velocity increases and reaches up to 2.2 times of maximum scour depth for single pier case. As the number of piles increase, the single scour holes are superposed and the overall scour hole turned out to be rectangular shape. The experimental results for the case of 35 piles indicate that the scour depth has the maximum value at angle of attack of 35 degree and that the main scour hole is formed in diagonal direction.

  • PDF

The Evaluation of Dynamic Group Pile Effect by the Analysis of Experimental p-y Curves (실험 p-y 곡선을 이용한 동적 군말뚝 효과 분석)

  • 김성렬;김성환;정충기;김명모
    • Journal of the Korean Geotechnical Society
    • /
    • v.18 no.1
    • /
    • pp.127-132
    • /
    • 2002
  • Shaking table tests are performed on model group piles to investigate the mechanics of dynamic pile-soil interaction, and to evaluate the dynamic group pile effect. Tests are executed on a single pile as well as group piles($3\times3$) by varying a pile spacing from 3D to 8D. A lumped mass is located on top of piles to simulate a superstructure. Dynamic p-y curves of the single pile and the group piles are obtained from the tests and compared with the backbone slopes of API cyclic p-y curves. From the comparisons, dynamic pile group effects are evaluated in terms of a pile spacing, a shaking frequency, and a shaking intensity.

Downdrag on a Single Pile and on Pile Groups (단독말뚝과 군말뚝의 Downdrag)

  • Jeong, Sang Seom
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.13 no.4
    • /
    • pp.259-268
    • /
    • 1993
  • The downdrag on a single pile and on pile groups was examined by using a numerical analysis and an analytical study. The overall objective of the present study was given to the magnitude and distribution of the downdrag forces on piles within a group. The case of the single pile was analyzed by developing a closed form solution. Subsequently the response of groups was investigated by using a detailed numerical approach. Based on the results, it is found that the downdrag load of piles in a group is much smaller than that of a single pile. Also, a simple method is proposed to design groups of 9 to 25 piles with spacing-to-diameter ratios varying from 2.5 to 5.0 for downdrag loads.

  • PDF

Interaction Factors of One-Row Pile Groups Subjected to Lateral Soil Movements (측방 유동을 받는 일렬 군말뚝의 상호 작용 계수)

  • Jeong, Snag-Seom;Kim, Byung-Chul
    • Journal of the Korean Geotechnical Society
    • /
    • v.16 no.3
    • /
    • pp.157-162
    • /
    • 2000
  • 측발유동을 받는 일렬 군말뚝의 그룹효과를 파악하이 위해 3차원 유한요소해석을 수행하였다. 국내의 대표적인 화강풍화토 지반에 선단지지된 말뚝을 대상으로 측방으로 지반변위 발생시 말뚝 두부조건과 중심간격(2.5D, 5.0D, 7.0D, 단독말뚝) 및 말뚝주면의 접촉효과를 고려한 군말뚝의 상호작용계수를 산정하였다. 본 연구 결과, 단독말뚝과 비교하여 군말뚝의 간격이 좁아짐에 따라 상호작용계수는 현저하게 감소하였으며 말뚝 두부조건이 회전구속, 힌지,자유단의 순으로 감소정도가 크게 나타났다. 이는 실내모형실험을 통해 산정된 상호작용계수와도 비교적 잘 일치함을 보였다.

  • PDF

Three-Dimensional Computational Modeling of Scour around Pile Groups (군말뚝 주변의 세굴 3차원 수치모의)

  • Kim, Hyung Suk;Park, Moonhyeong
    • Journal of Korea Water Resources Association
    • /
    • v.47 no.10
    • /
    • pp.907-919
    • /
    • 2014
  • This study presents scour processes and its characteristics around the pile groups using the large eddy simulation (LES) coupled with sediment transport and morphodynamic models. The scour and deposition around pile groups were significantly influenced by the pile interval. In case the non-dimensional pile interval was less than 3.75, the local scours as well as the contraction scour were observed around the pile group. On the other hand, in case the non-dimensional pile interval was more than 3.75, the contraction scour disappeared and only local scours were developed at individual piles. Change in the scour depth at piles located in the upstream was similar with the case of single pile, but the scour depth around piles located in the downstream was lower and showed a significantly different tendency due to the presence of piles in the upstream. The non-dimensional maximum scour depth around the pile group decreased as the pile interval increased.

Lateral Behavior of Group Pile in Sand (사질토 지반에서 군말뚝의 수평거동에 관한 연구)

  • 김영수;김병탁
    • Journal of the Korean Geotechnical Society
    • /
    • v.16 no.1
    • /
    • pp.117-129
    • /
    • 2000
  • This paper discusses the lateral behavior of group pile in homogeneous and non- homogeneous (two layered) soil. In the group pile, the model tests were to investigate the effects on spacing-to-diameter ratio of pile, pile array, ratio of pile spacing, constraint condition of pile tip, eccentric load and ground condition. The group efficiency and lateral deflection induced in active piles were found to be highly dependent on the spacing-to-diameter ratio of pile, number of pile. Lateral bearing capacities in the group piles of fixed tip, in the case of 6D spacing and $3\times3$ array, were 40-100% higher than those in the group pile of free tip. Based on the results obtained, a spacing-to-diameter of 6.0 seems to be large enough to eliminate the group effect for the case of relative density of 61.8% and 32.8%, and then each pile in such a case behaves essentially the same as a single pile. However, in the case of dense sand, it can be estimated that a spacing-to-diameter of 8.0 seems to be large enough to eliminate the group effect. In this study the group efficiency is illustrated in experimental function with spacing-to-diameter, S/D, relative density and number of pile. The distribution of shear force in lead row piles, in the case of 3$\times$3 array group pile, was 41.6-52.4% for 3D spacing and 34-40% for 6D spacing, respectively. The shadowing effect for the parallel direction of lateral loading appears to be more significant than the one for the perpendicular direction of lateral loading.

  • PDF

Evaluation of Dynamic Group Pile Effect in Dry Sand by Centrifuge Model Tests (원심모형 실험을 이용한 건조토 지반에서의 군말뚝 효과 분석)

  • Yoo, Min-Taek;Cha, Se-Hwan;Choi, Jung-In;Han, Jin-Tae;Kim, Myoung-Mo
    • Journal of the Korean Geotechnical Society
    • /
    • v.28 no.1
    • /
    • pp.67-77
    • /
    • 2012
  • In this study, a series of centrifuge shaking-table tests for a $3{\times}3$ group pile and a single pile applied by sinusoidal wave was performed in dry sand for various pile spacings, ranging from three to seven times the pile diameter. A comparison of centrifuge tests of both single pile and group pile showed that the lateral ground response of the group pile was smaller than that of the single pile. In addition, the reduction in subgrade reaction for the group pile increased with decreasing pile spacing. The side piles, that is, the 1st row and 3rd row piles showed identical dynamic p-y behavior and the center pile in the 2nd row caused a lower reduction effect compared with the 1st and 3rd row piles. From the comparison between the p-y curves of the 2nd row piles, it was found that the lateral ground response of the outer pile in the 2nd row was less than that of the center pile in the 2nd row. The p-multipliers for the side piles, for the center pile and for the outer pile ranged from 0.28 to 0.77, from 0.55 to 1.0 and from 0.39 to 0.87, respectively.

Earthquake-resistance Analysis of Piles Using Dynamic Winkler Foundation Model (동적 Winkler 보 모델을 이용한 말뚝의 내진해석)

  • 장재후;유지형;정상섬
    • Journal of the Korean Geotechnical Society
    • /
    • v.18 no.2
    • /
    • pp.39-49
    • /
    • 2002
  • This paper describes a numerical method for pile foundation subjected to earthquake loading using dynamic Winkler foundation model. To verify the numerical method, shaking table tests were carried out. In shaking table tests, accelerations and pile bending moments were measured for single pile and pile groups with a spacing-to-diameter ratio of 2.5 under fixed input base acceleration. In numerical analysis, the input base and free field accelerations measured from shaking table tests were used as input base motions. Based on the results obtained, free field acceleration was magnified relative to input base acceleration, whereas pile head accelerations reduced relatively to free field acceleration for soil-pile interaction. Measured and predicted bending moments for both cases have maximum value within the distance 10cm(4d) from the pile top. However, there are some differences between the results of numerical analysis and shake table test below 10cm(4d) from the pile top.

Group Effects in Pile Group under Lateral Loading (수평력을 받는 군말뚝에서의 말뚝의 상호작용)

  • Ahn Kwang Kuk;Kim Hong Taek
    • Journal of the Korean Geotechnical Society
    • /
    • v.21 no.2
    • /
    • pp.47-55
    • /
    • 2005
  • This paper describes the results for a numerical analysis of'single piles and pile oops in clayey soils subjected to monotonous lateral loading using the ABAQUS finite element software. The investigated variables in this study include free head and embedded capped single piles, pile diameter (1.0 m, 0.5 m), pile length (7.0 m, 10.0 m), and pile groups. The 1$\times$3 pile group was selected to investigate the individual pile and group lateral resistance, the distribution of the resistance among the piles, the effects of lateral stresses in front of and on the sides of the piles, and the effect of a cap on the lateral resistance of the leading pile. The soil was modeled using Cam-clay constitutive relationship and the pile was considered as a elastic circular concrete pile. The results show that the size of the cap influences lateral capacity of sin pile. The results also show in pile groups, the pile-soil-pile interaction and the cap effect the resistance in the leading pile, and the p-multiplier for the leading pile of greater than 1.0 was able to be obtained.