• Title/Summary/Keyword: Pullout deformation

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Discrete element modelling of geogrids with square and triangular apertures

  • Chen, Cheng;McDowell, Glenn;Rui, Rui
    • Geomechanics and Engineering
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    • v.16 no.5
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    • pp.495-501
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    • 2018
  • Geogrid application that has proved to be an effective and economic method of reinforcing particles, is widely used in geotechnical engineering. The discrete element method (DEM) has been used to investigate the micro mechanics of the geogrid deformation and also the interlocking mechanism that cannot be easily studies in laboratory tests. Two types of realistically shaped geogrid models with square and triangle apertures were developed using parallel bonds in PFC3D. The calibration test simulations have demonstrated that the precisely shaped triangular geogrid model is also able to reproduce the deformation and strength characteristics of geogrids. Moreover, the square and triangular geogrid models were also used in DEM pull-out test simulations with idealized shape particle models for validation. The simulation results have been shown to provide good predictions of pullout force as a function of displacement especially for the initial 30 mm displacement. For the granular material of size 40 mm, both the experimental and DEM results demonstrate that the triangular geogrid of size 75 mm outperforms the square geogrid of size 65 mm. Besides, the simulations have given valuable insight into the interaction between particle and geogrid and also revealed similar deformation behavior of geogrids during pullout. Therefore, the DEM provides a tool which enable to model other possible prototype geogrid and investigate their performance before manufacture.

Development Strength of Headed Reinforcing Bars for Steel Fiber Reinforced Concrete by Pullout Test

  • Kim, Seunghun;Paek, Sungchol;Lee, Changyong;Yuk, Hyunwoong;Lee, Yongtaeg
    • Architectural research
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    • v.20 no.4
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    • pp.129-135
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    • 2018
  • In order to compare the development performance of headed reinforcing bar and straight reinforcing bar in tension for steel fiber reinforced concrete (SFRC), pullout test of specimens with reinforcing bar which was anchored on simple beam perpendicularly was conducted. The experimental variables were steel fiber volume ratio ($V_{Rsf}$), concrete compressive strength, and existence of head. As the result of test, splitting failure of concrete in the development direction of reinforcing bar in most specimens was observed. For development detail of headed reinforcing deformation bar, specimens with 1% $V_{Rsf}$ showed approximately 63%~119% increase in pullout strength compare to specimens with 0% $V_{Rsf}$. Test result shows that SFRC is more effective in increasing pullout strength for headed reinforcing bars than increasing pullout strength of straight bars.

Evolution of pullout behavior of geocell embedded in sandy soil

  • Yang Zhao;Zheng Lu;Jie Liu;Jingbo Zhang;Chuxuan Tang;Hailin Yao
    • Geomechanics and Engineering
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    • v.38 no.3
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    • pp.275-284
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    • 2024
  • This paper aims to explore the evolution of the pullout behavior of geocell reinforcement insights from three-dimensional numerical studies. Initially, a developed model was validated with the model test results. The horizontal displacement of geocells and infill sand and the passive resistance transmission in the geocell layer were analyzed deeply to explore the evolution of geocell pullout behavior. The results reveal that the pullout behavior of geocell reinforcement is the pattern of progressive deformation. The geocell pockets are gradually mobilized to resist the pullout force. The vertical walls provide passive pressure, which is the main contributor to the pullout force. Hence, even if the frontal displacement (FD) is up to 90m mm, only half of the pockets are mobilized. Furthermore, the parametric studies, orthogonal analysis, and the building of the predicted model were also carried out to quantitative the geocell pullout behavior. The weights of influencing factors were ranked. Ones can calculate the pullout force accurately by inputting the aspect ratio, geocell modulus, embedded length, frontal displacement, and normal stress.

Charateristics of the Jointed Steel-Grid Reinforcement and the Application (결합강그리드보강재의 특성 및 적용)

  • Han, Jung-Geun
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.5 no.3
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    • pp.15-22
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    • 2002
  • To analysis of the embanked slope stability using a jointed reinforcement, the internal stability and the external stability have to be satisfied, respectively. But, because the lengths of ready-made steel-grid were limited, the reinforcements must be connecting themselves to the reinforcing. In this study, the mechanical test was carried out to investigate the tensile failure and the pullout failure at the joint parts of them, which was based on the analysis of reinforced slope in field. Through the tensile tests in mid-air for the jointed steel-grid, the deformation behavior was seriously observed as follows : deformation of longitudinal member, plastic deformation of longitudinal member and of crank part. Those effects were due to the confining pressure and overburden pressure of the surrounding ground. The bearing resistance at jointed part of jointed steel-grid was due to the latter only. The maximum tensile forces were higher about 20kN~27kN than ultimate pullout resistance, but, the results of those was almost the same in mid-soil. The failures of steel-grid occurred at welded point both of longitudinal members and transverse members and of jointed parts. The strength of jointed parts itself got pullout force about 20kN, which was about 65% for ultimate pullout force of the longitudinal members N=2. To the stability analysis of reinforced structure including the reinforced slope, the studying of connection effects at jointed part of reinforcement members must be considered. Through the results of them, the stability of reinforced structures should be satisfied.

A Study on the Behaviour Mechanism of Jacket Anchor (자켓앵커 거동특성에 관한 연구)

  • Kim, Dong-Hee;Kim, In-Chul;Kong, Hyun-Seok;Lee, Woo-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.1240-1249
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    • 2008
  • Jacket anchor was developed to increase the pullout resistance of general ground anchor in soft ground, and the mechanism of pullout resistance of jacket anchor was analyzed. Also, the ultimate bond stress of jacket anchor was estimated by ultimate resistance which is determined by field tests. Grout milk was injected into the jacket to make grout bulb of jacket anchor. The formation of grout bulb of jacket anchor increases the diameter of grout bulb, ground strength and confining pressure between anchor grout and soil. From the twelve field test results, it was observed that the pullout resistance of jacket anchor is 15.38~295.02%(average 83.53%) greater than that of general ground anchor, and plastic deformation of jacket anchor is 20.78~1,496.45%(average 288.78%) smaller than that of general ground anchor at the same load cycle. Especially, it was investigated that the increase of ultimate resistance over 200% and the reduction of plastic deformation over 600% was obtained in gravel layer. It means that the jacket anchor is superior to the general ground anchor in gravel layer. Finally, the ultimate bond stress was proposed to design jacket anchor.

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Evaluations of load-deformation behavior of soil nail using hyperbolic pullout model

  • Zhang, Cheng-Cheng;Xu, Qiang;Zhu, Hong-Hu;Shi, Bin;Yin, Jian-Hua
    • Geomechanics and Engineering
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    • v.6 no.3
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    • pp.277-292
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    • 2014
  • Soil nailing, as an effective stabilizing method for slopes and excavations, has been widely used worldwide. However, the interaction mechanism of a soil nail and the surrounding soil and its influential factors are not well understood. A pullout model using a hyperbolic shear stress-shear strain relationship is proposed to describe the load-deformation behavior of a cement grouted soil nail. Numerical analysis has been conducted to solve the governing equation and the distribution of tensile force along the nail length is investigated through a parametric study. The simulation results are highly consistent with laboratory soil nail pullout test results in the literature, indicating that the proposed model is efficient and accurate. Furthermore, the effects of key parameters, including normal stress, degree of saturation of soil, and surface roughness of soil nail, on the model parameters are studied in detail.

The Pullout Behavior of a Large-diameter Batter ]Reaction Piles During Static Pile Load Test for a Large Diameter Socketed Pipe Pile (대구경 말뚝의 정재하시험시 대구경 경사반력말뚝의 인발거동)

  • 김상옥;성인출;박성철;정창규;최용규
    • Journal of the Korean Geotechnical Society
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    • v.18 no.1
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    • pp.5-16
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    • 2002
  • The pullout behavior of large-diameter steel pipe piles(diameter = 2,500mm, length = 38~40m), which were designed as compression piles but used as reaction piles during a static compression load test on a pile(diameter = 1,000m, length = 40m), was investigated. The steel pipe piles were driven by 20m into a marine deposit and weathered soil layer and then socketed by 10m into underlying weathered and soft rock layers. The sockets and pipe were filled with reinforced concrete. The steel pipe and concrete in the steel pipe zone and concrete and rebars in the socketed zone were fully instrumented to measure strains in each zone. The pullout deformations of the reaction pile heads were measured by LVDTs. Over the course of the study, a maximum uplift deformation of 7mm was measured in the heads of reaction piles when loaded to 10MN, and 1mm of residual uplift deflection was measured. In the reaction piles, about 83% and about 12% of the applied pullout loads were transferred in the weathered rock layer and in the soft rock layer, respectively. Also, at an uplift force of 10MN, shear stresses due to the uplift in the weathered rock layer md soft rock layer were developed as much as 125.3kPa and 61.8kPa, respectively. Thus, the weathered rock layer should be utilized as resisting layer in which frictional farce could be mobilized greatly.

Analysis of Load Capacity and Deformation Behavior of Suction Pile Installed in Sand (모래지반에 근입된 석션파일의 인발저항력 및 변위거동 분석)

  • Kim, You-Seok;Jang, Yeon-Soo
    • Journal of the Korean Geotechnical Society
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    • v.27 no.11
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    • pp.27-37
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    • 2011
  • A series of centrifuge model tests to investigate the suction pile pullout loading capacity in sand have been performed. The main parameters that affect the pullout loading capacity of a suction pile include the mooring line inclination angle and the padeye position of the suction pile. With respect to the padeye position, the maximum pullout loading capacity is obtained when the padeye position is near 75% of the pile length from the top. The direction of the pile rotation changes when the padeye position reaches somewhere near 50~75% for all mooring line inclination angles. The translation displacement of suction pile to develop the time of maximum pullout loading capacity decreased as the mooring line inclination angle increased. In addition, the vertical displacements of the center of a suction piles for all cases appeared to develop toward the ground surface.

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.

Failure Modes of Vertical Ground Anchor in Plane Strain (평면변형률 상태에 있는 연직지반앵커의 파괴모-드)

  • Im, Jong-Cheol;;Park, Seong-Jae
    • Geotechnical Engineering
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    • v.6 no.1
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    • pp.43-58
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    • 1990
  • In order to get ultimate pullout resistance of ground anchor, the position of failure surface, normal stress and friction angle on the failure surface should be known. In this study, the position of failure surface is obtained by observing deformation of ground around anchor, and stresses on the anchor surface are analyzed by measuring normal and shear stresses on the anchor surface through model anchor test in plane strain. In addition, the relationship between lateral earth pressure and the position of failure surface is analyzed and the formula for calculating ultimate pullout resistance of anchor is proposed by using non-dimensional coefficient of ultimate pullout resistance.

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