Shearing Characteristics of The Hydraulic-filled Sands With Flat Particle

• Main Authors: Jeng, Ching-Jiang, 鄭清江
• Other Authors: John C. Li
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/31273077610745966264

博士 === 國立中央大學 === 土木工程學系 === 84 === The fabric orientation of hydraulic-filled sand with flat particles is quite different from the general compacted sand. This difference will affect their shearing characteristics. In this research, a sand-water mixture transportation device was developed to prepare testing specimens. The microanalysis of thin sections on soil fabric is conducted to observe the arrangement of particles under different conditions. Then, a series of static and dynamic shearing tests on wet-tamped sand specimen and hydraulic-filled sand specimen are performed to find out various influence factors of steady state. The steady state lines for each condition are obtained from static shearing tests. State parameter of each specimen is then calculated based on its corresponding steady state line. The correlation between state parameter and shearing characteristics is investigated. Finally, cyclic simple shearing tests and cyclic triaxial tests are carried out to evaluate the liquefaction resistance and cyclic deformation. The results observed from microanalysis is used to verify and discuss the phenomenon of shearing behavior. Refer to all results obtained, the following conclusions can be achieved : (1)A sand-water mixture transportation device was developed to study the hydraulic-filled sand. This testing device can also be used to simulate the natural deposition in similar researches, such as riverbed, reservoir or sedimentation basin. (2) In this study, the particle characteristics of the tested soil is obtained and the results are validated by comparing with geological references. For a specific shape and particle stacking behavior during hydraulic deposition, a particular fabric orientation can be found. Consequently, a better suggestion about sample formulation and testing method can be proposed. (3)The results of the simulated hydraulic-filled sand with flat particles obtained from this research may clarify the contradiction between other researches caused by different sample preparation. (4)In this research, a better understanding on the mechanism and shearing behavior of hydraulic-filled sand has been observed. Moreover, valuable reference are also provided to the analysis and planning in hydraulic reclamation project. (5)The steady state lines for each condition of testing soil are obtained. The correlation between state parameter and shearing properties is proved to be applicable in such flat-particle sand. Moreover, the correlation curves showed in this research can be a reference in engineering practice. (6)This study has overcome the obstacle of resin impregnation in moist specimen. The process for microanalysis of thin section on sand specimen was developed and can be a reference for the further research of granular soil. In addition, it is indicated that the variation of initial void ratio, drainage conditions, stress state, anisotropic consolidation ratio and pore fluid has no significant effect on the achievement of steady state line. On the other hand, the compressibility of the specimen will increase with respect to fines content. Therefore, the slope of the steady state line would be steeper. Moreover, both sample preparation method and stress path (compression or extension) conditions do influence the results of steady state, this might be attribute to the difference of fabric orientation with respect to principal stress direction. Although fines content, initial fabric and stress path conditions affect the results of steady state line, but it is indicated that the state parameter calculated based on each steady state line is a dependent of undrained shearing strength and pore water pressure parameter. Similar trend can be obtained when compare with the results of other references using different kinds of testing sand. In other words, the state parameter can be used as a definite correlation factor for undrained shearing strength and pore water pressure parameter in various conditions. Consequently, the application of state parameter to evaluate the shearing characteristics of hydraulic filled sand are prospective. In cases of cyclic simple shearing tests, the liquefaction resistance of hydraulic transportation specimen is lower than that of wet-tamped specimen. However, in dynamic triaxial test, the liquefaction resistance of formal specimen is higher than the latter. These phenomena demonstrate that the anisotropic characteristics of the testing soil will also influence the liquefaction resistance and dynamic deformation behavior. For hydraulic transportation specimen, the particle orientation during stacking process tends to be in horizontal direction. This makes the liquefaction resistance obtained from simple shearing test, which also applys shear force in horizontal direction, becomes lower than the liquefaction resistance obtained from cyclic triaxial test which applys force in vertical direction. Consequently, the fabric orientation and the direction of applying shearing stress should be considered adequately for flat shaped hydraulic-filled sand in engineering application. Although these two specimens are equal in relative density but its liquefaction resistance is different because of their fabric discrepancy. When comparison based on state parameter is made between these two specimens, a consistent tendency can be obtained that the lower the state parameter is the higher the liquefaction resistance will be. Therefore, state parameter can provide help in evaluation of liquefaction potential for the flat shaped hydraulic- filled sand.