• Geomechanics and Engineering
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• 제14권3호
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• pp.233-240
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• 2018

Pullout tests are usually employed to determine the ultimate bearing capacity of reinforced soil, and the load-displacement curve can be obtained easily. This paper presents an analytical solution for predicting the full-range mechanical behavior of a buried planar reinforcement subjected to pullout based on a bi-linear bond-slip model. The full-range behavior consists of three consecutive stages: elastic stage, elastic-plastic stage and debonding stage. For each stage, closed-form solutions for the load-displacement relationship, the interfacial slip distribution, the interfacial shear stress distribution and the axial stress distribution along the planar reinforcement were derived. The ultimate load and the effective bond length were also obtained. Then the analytical model was calibrated and validated against three pullout experimental tests. The predicted load-displacement curves as well as the internal displacement distribution are in closed agreement with test results. Moreover, a parametric study on the effect of anchorage length, reinforcement axial stiffness, interfacial shear stiffness and interfacial shear strength is also presented, providing insights into the pullout behaviour of planar reinforcements of MSE structures.

• Geomechanics and Engineering
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• 제34권6호
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• pp.623-636
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• 2023

This study utilized small-scale physical model tests to investigate the impact of different types of geosynthetics, including geocell, planar geotextile, and wraparound geotextile, on the behaviour of strip footings placed on 0.8 m thick soil fills and backfills with a slope angle of 70°. Bearing capacity and settlement of the footing and failure mechanisms are discussed and evaluated. The results revealed that the bearing capacity of footings situated on both unreinforced and reinforced slopes increased with a greater embedment depth of the footing. For settlement ratios below 4%, the geocell reinforcement exhibited significantly higher stiffness, carrying greater loads and experiencing less settlement compared to the planar and wraparound geotextile reinforcements. However, the performance of geocell reinforcement was influenced by the number and length of the geocell layers. Increasing the geocell back length ratio from 0.44 to 0.84 significantly improved the bearing capacity of the footing located at the crest of the reinforced slope. Adequate reinforcement length, particularly for geocell, enhanced the bearing pressure of the footing and increased the stiffness of the slope, resulting in reduced deflections. Increasing the length of reinforcement also led to improved performance of the footing located on wraparound geotextile reinforced slopes. In all reinforcement cases, reducing the vertical spacing between reinforcement layers from 100 mm to 75 mm allowed the slope to withstand much greater loads.

• 한국주조공학회지
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• 제16권6호
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• pp.537-549
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• 1996

This study aims at investigating the correlation of microstructure and mechanical properties of the AZ91 Mg/Al borate whisker composites fabricated by squeeze csting technique with a variation of applied pressure. Microstructure observation and in-situ fracture tests were conducted on the composites to identify the microfracture process. Detailed microstructural analyses indicated that the grain refinement could be achieved with applied pressure and the little change in volume fraction on reinforcing whiskers could be carried out. It was also found clearly from in-situ observation of crack initiation and propagation that in the composite processed by the lower applied pressure, microcracks were initiated earily at whisker/matrix interfaces, thereby resulting in the drop in strength. In the composite processed by the higher applied pressure, on the other hand, planar slip lines were well developed in the matrix, and then propagated through whiskers without whisker/matrix decohesion. Thus, the effect of the applied pressure on microstructure and mechanical properties can be explained by grain refinement, increased amounts of reinforcements, and improvement of whisker/matrix interfacial strength as the applied pressure in increased.

• Composites Research
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• 제22권5호
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• pp.15-23
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• 2009

가압주조법으로 제조한 $Al_2O_3$ 섬유와 SiC 입자 혼합 보강 금속복합재료(MMCs)의 상온과 고온에서 윤활마모특성을 조사하였다. 마모시험은 거리와 온도의 변화에 따라 속도를 고정시켜 25Kgf의 하중하에서 수행하였으며 MMCs의 시험편은 가압의 수평(PR)방향과 수직(N)방향에서 채취하였다. 혼합비의 영향을 관찰한 결과 상온에서는 20%섬유만 보강한 PR방향 MMCs의 마모거동은 N방향 보다 우수한 결과를 보였으나, 혼합보강 MMCs는 반대로 나타내었다. 고온($100^{\circ}C$)에는 모든 MMCs에서 PR방향의 마모거동이 N 방향보다 우수한 결과를 보인 것은 보강재와 마찰면간 윤활필름이 강호작용에 기인한 것으로 밝혀졌다. $150^{\circ}C$에서는 혼합 MMCs의 마모거동은 온도영향으로 PR이 N 보다 우수한 결과를 보였다.