• Title/Summary/Keyword: ultimate soil resistance

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A Study on the Strength Evaluation of Micropile with Expanded Drill Hole (확공형 마이크로 파일의 강도 평가에 관한 연구)

  • Lee, Jae-Min;Kim, Doo-Hwan
    • Journal of the Korean Society of Safety
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    • v.29 no.5
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    • pp.74-81
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    • 2014
  • This study proposes an advanced type of a micropile system. The proposed micropile system consists of perfobond ribs installed steel rod to improve shear capacity between the thread and the grout, and partially expanded drill holes to increase resistance capacity between the grout and the ground. This study contains experimental evaluations on the proposed micropile system to verify the shear capacity of perfobond rib installed on the steel rod and the load-carrying capacity of shear key created by the partially expanded drill hole. Push-out tests were conducted on a rolled screw thread and steel rods which perfobond ribs are installed instead of rolled screw, in order to compare their load-carrying capacity and behavioral characteristics. As a result, it was confirmed that the perfobond-rib steel rods show much superior structural behavior in terms of initial stiffness, ultimate load, and ductile behavior.

Nonlinear response of laterally loaded rigid piles in sand

  • Qin, Hongyu;Guo, Wei Dong
    • Geomechanics and Engineering
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    • v.7 no.6
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    • pp.679-703
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    • 2014
  • This paper investigates nonlinear response of 51 laterally loaded rigid piles in sand. Measured response of each pile test was used to deduce input parameters of modulus of subgrade reaction and the gradient of the linear limiting force profile using elastic-plastic solutions. Normalised load - displacement and/or moment - rotation curves and in some cases bending moment and displacement distributions with depth are provided for all the pile tests, to show the effect of load eccentricity on the nonlinear pile response and pile capacity. The values of modulus of subgrade reaction and the gradient of the linear limiting force profile may be used in the design of laterally loaded rigid piles in sand.

Pull-out Test of Pulse Powered Underreamed Anchors (펄스방전 확공형 앵커의 현장시험)

  • Kim, Nak-Kyung;Ju, Yonh-Sun;Kim, Sung-Kyu;Seo, Hyo-Kyun;Kim, Tae-Hun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.1014-1021
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    • 2008
  • Ground anchor should not be used in soft clay, because anchor resistance can not be guaranteed. However, there is a way to increase the capacity of anchors. The pulse powered anchor is an underreamed anchor by using high voltage electrokinetic pulse energy. In this paper, conceptual introduction of the pulse powered anchor was presented. Anchor pull-out tests were performed at the Geotechnical Experimentation Site at Sungkyunkwan University in Suwon, Korea. Data were analyzed in order to verify the performance of pulse powered anchors.

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Constructing Database and Probabilistic Analysis for Ultimate Bearing Capacity of Aggregate Pier (쇄석다짐말뚝의 극한지지력 데이터베이스 구축 및 통계학적 분석)

  • Park, Joon-Mo;Kim, Bum-Joo;Jang, Yeon-Soo
    • Journal of the Korean Geotechnical Society
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    • v.30 no.8
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    • pp.25-37
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    • 2014
  • In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.

Evaluation of Dynamic p-y Curves of Group Piles Using Centrifuge Model Tests (원심모형실험을 이용한 무리말뚝의 동적 p-y 곡선 산정)

  • Nguyen, Bao Ngoc;Tran, Nghiem Xuan;Kim, Sung-Ryul
    • Journal of the Korean Geotechnical Society
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    • v.34 no.5
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    • pp.53-63
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    • 2018
  • Dynamic soil-pile interaction is the main concern in the design of group piles under earthquake loadings. The lateral resistance of the pile group under dynamic loading becomes different from that of a single pile due to the group pile effect. However, this aspect has not yet been properly studied for the pile group under seismic loading condition. Thus, in this study the group pile effect was evaluated by performing a series of dynamic centrifuge tests on $3{\times}3$ group pile in dry loose sand. The multiplier coefficients for ultimate lateral resistance and subgrade reaction modulus were suggested to obtain the p-y curve of the group pile. The suggested coefficients were verified by performing the nonlinear dynamic analyses, which adopted Beam on Nonlinear Winkler Foundation model. The predicted behavior of the pile group showed the reasonable agreement compared with the results of the centrifuge tests under sinusoidal wave and artificial wave.

An Experimental Study on Pullout Behavior of Shallow Bearing Plate Anchor (얕은 지압형 앵커의 인발거동특성에 관한 실험적 연구)

  • Hong, Seok-Woo;Kim, Hyung-Kong
    • Journal of the Korean Geotechnical Society
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    • v.30 no.2
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    • pp.5-18
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    • 2014
  • Depending on the underground load support mechanism, anchors are classified as friction anchors, bearing plate anchors and the recently developed combined friction-bearing plate anchors which combine the characteristics of both the friction and bearing plate type anchors. Even though numerous studies have been performed on bearing plate anchors, there were only few studies performed to observe the failure surface of bearing plate anchors. Furthermore most of the soil materials used on these tests were not real sand but carbon rods. In this study, sand was placed in the soil tank and laboratory tests were performed with bearing plate anchors installed with an embedment depth (H/h) ranging from 1~6. The variation in the pullout capacity and the behaviour of soil with the embedment depth (H/h) were observed. Ground deformation analysis program was also used to analyze soil displacement, zero extension direction, maximum shear strain contours. It was determined from the analysis of the results that at ultimate pullout resistance the deformation was 5 mm and the failure surface occurred in a narrower area when compared with results of the previous researches. It was also observed that the width of the fracture surface gradually becomes wider and expands up to the surface as the deformation increases from 10 mm to 15 mm.

Evaluation of Lateral Pile Behavior under Cyclic Loading by Centrifuge Tests (원심모형 실험을 이용한 반복하중을 받는 모노파일 거동 평가)

  • Lee, Myungjae;Yoo, Mintaek;Park, Jeongjun;Min, Kyungchan
    • Journal of the Korean Geotechnical Society
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    • v.35 no.6
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    • pp.39-48
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    • 2019
  • This study investigated the lateral behavior of monopile embedded in the dry sand through cyclic lateral loading test using a centrifuge test. The sand sample for the experiment was the dry Jumunjin standard sand at 80% relative density and the friction angle of $38^{\circ}$. In the experimental procedure, firstly, it was determined the static lateral bearing capacity by performing the static lateral loading test to decide the cyclic load. This derived static lateral bearing capacity values of 30%, 50%, 80%, 120% were determined as the cyclic lateral load, and the number of cycle was performed 100 times. Through the results, the experiment cyclic p-y curve was calculated, and the cyclic p-y backbone curve by depth was derived using the derived maximum soil resistance point by the load. The initial slope at the same depth was underestimated than API (1987) p-y curves, and the ultimate soil resistance was overestimated than API (1987) p-y curves. In addition, the result of the comparison with the suggested dynamic p-y curve was that the suggested dynamic p-y curve was overestimated than the cyclic p-y backbone curve on the initial slope and soil resistance at the same depth. It is considered that the p-y curve should be applied differently depending on the loading conditions of the pile.

A Study of Point Selection for Loading Cells in Bi-directional Pile Load Test (양방향재하시험에서 재하장치 위치 선정에 관한 연구)

  • Yoon, Minseung;Kim, Junwoo;Kim, Myunghak
    • Journal of the Korean GEO-environmental Society
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    • v.14 no.10
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    • pp.11-16
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    • 2013
  • Success or failure of the bi-directional pile load test for drilled shaft depends on point selection for loading cells, that is balanced location both uplift force and downward force. Methods to evaluate the ultimate unit side resistance in rockmass layer in both domestic and foreign are based on the uniaxial compression strength of rock core, which can hardly be obtained in domestic rockmass layers which are weathered rockmass layer and soft rockmass layer with very low RQD. Therefore, this study suggested the relation charts between the revised SPT N values and developed unit side resistance of each different layers, which were obtained from bi-directional pile load tests in various domestic sites. To evaluate the appropriateness of the relation charts, the developed unit side resistances from the relation charts were used to select the loading cell position and compared with the measured unit side resistances from field pile load test. Results showed that the developed side resistance from relation charts and the measured side resistance of weathered soil layer and weathered rock layer were very close. Average developed side resistance($1,325kN/m^2$), which are average of upper soft rock layer of loading device($1,151kN/m^2$) and lower($1,500kN/m^2$), was similar with the estimated value ($1,250kN/m^2$).

A Study on the Characteristics of Bearing Capacity for Rammed Aggregate Pier in Sand (사질토지반에서 짧은 쇄석다짐말뚝의 배치형태에 따른 지지력특성에 관한 연구)

  • Chun, Byung-Sik;Kim, Young-Hun;Yoo, Woo-Hyun;Kim, Jong-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.195-198
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    • 2009
  • Rammed Aggregate Pier method is intermediate foundation of deep and shallow foundation, it has been built on world wide. But the investigation and research in domestic is not accomplished. In this paper, examined details of different spacing of piles, bearing capacities, respectively, conclude with recommendations on how RAP can be used in future needs. This documentation further provides comparisons of the laboratory test results which were obtained from differenciate the spacing of piles, namely installed rammed aggregate pier. Strain control test was conducted to determine the bearing capacities of the piers; 20mm, 30mm and 40mm diameter drilling equipment to drill holes were installed in sand at initial relative densities of 40%. By comparing different spacing of piles, in this experiment, piles are spaced structually span, form a ring shape, narrowing the distance of each other, to the center. the result shows that as diameter of pier is bigger in diameter, bearing capacity also dramatically increased due to raised stiffness. Also, the space between each piers narrowed, settlement rate of soil was decreased significantly. From the test results, as the space between each piles were getting closer, allows greater chances to have resistance to deformation, shows improved stability of structures.

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Axial Behavior of Non-Displacement Tapered Piles in Sand (모래지반에서 비배토 테이퍼말뚝의 연직거동 특성)

  • Paik, Kyu-Ho;Lee, Jun-Hwan;Kim, Dae-Hong
    • Journal of the Korean Geotechnical Society
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    • v.23 no.8
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    • pp.35-45
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    • 2007
  • It is known that the response of piles is affected by the shape of pile as well as soil conditions. In order to investigate the characteristics of the axial responses and bearing capacities of non-displacement tapered and cylindrical piles in sands, 12 model pile load tests using a calibration chamber were conducted on model tapered and cylindrical piles, which were specially manufactured to measure the base and shaft load capacities independently. Results of the model tests showed that the shaft load of tapered piles continuously increased with pile settlement, whereas the shaft load of cylindrical piles reached ultimate values at a settlement equal to 4% of pile diameter. Therefore, taper piles have greater shaft loads than cylindrical one at the same settlement. It is also observed that the total load capacity of tapered piles is lower than cylindrical piles for dense sand but is greater than that of cylindrical piles for medium sand. The ultimate unit base resistance of tapered piles was greater than that of cylindrical piles for lateral earth pressure ratio greater than 0.4, and the shaft resistance was greater than that of cylindrical piles irrespective of lateral earth pressure ratio.