Effect of Confining Pressure, Relative Density and Shear Strain on the Poisson’s Ratio of Clean Sand

摘要

In comparison to other dynamic properties of soil, Poisson’s ratio is mostly considered as an elastiudc udconstant. The effect of uddifferent paraudmeters on the Poisson’s ratio of soil is neglected in most of theudavailableudliterature. udProper estimation of the Poisson’s ratio is required as it signifies the stress and uddeformation characteristics of the soil. udIn udthis study a series of resonant column tests were performed to uddetermine the variation of Poisson’s ratio with confining pressure, relative density and shear straiudn. udClean udsand free from fines contentudwas used in this studyud. The tests were performed on saudnd sample of udsize 50 udud100 mm compacted at relative densities udof ud30%, 50% and 75ud%. udThe sample preparation udwasuddoneudby udusing a split mold. udBudy using a funnelud,udtudhe sand udwasudgently poured into the split mold. Then each udlayer udwasudcompacudted by means of a tamping rod which weighs 150udg. The sample preparation udwasuddone udin 5 equal thick layers. By udperformingudfew trial sample preudparationsud, the number of blows required per udlayer for a desired relative density udwasuddetermined. udA fixed free type udof resonant column was used in this udstudyud. By performing the resonant column test in torsional mode as well as flexural mode of excitationud, itudis possible to estimate the Poisson’s ratio of the soil. The confining pressure udwasudvaried from 100 kPa to ud800 kPuda. The shear strain udvariudedudfrom 10ud-ud4ud% to 10ud-ud1ud%. udFigure 1 gives the variation of Poisson’s ratio with confining pressure for various relative densitiudes. From udthe figure iudt is observed that there is uda udcontinuous decrease in Poisson’s ratio of the soil witudh udan udincrease udinudtheudconfining pressure as well as relative density. The percentage reduction in Poisson’s ratio obtainedudfor the soil subjected to a confining pressure of 800 kPa as compared to soil subjected to 100 kPa udconfining pressure is ud19 %, 21 % anudd 22ud% for 30 %, 50 %, 75 % relative densities of the soil.udIn addition,udthe percentageudsudreduction in Poisson’s ratio of sand prepared at 75 %udrelative densityudas compare udto ud30 % udrelative density udareud14 %, 15.7 %, 16.7 % and 17.6 % udfor sand subjected to 100udkPa, 400 kPa, 60ud0 kPa udand 800 kPa respectivelyud. It udcan be concluded udthat the percentage reduction in Poisson’s ratio increases udwith the increase in confining pressure as well as relative density.