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2018, vol. 61, br. 1, str. 47-61
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Statičko i dinamičko vrednovanje elastičnih svojstava peska iz Sofije i Tojoura sofisticiranim triaksijalnim opitom
Static and dynamic evaluation of elastic properties of Sofia sand and Toyoura sand by sophisticated triaxial tests
aYoda Ltd., Parter, Pavlovo, Sofia, Bulgaria bJunichi Koseki, University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
e-adresa: n.milev@yoda-bg.com, koseki@civil.t.u-tokyo.ac.jp
Sažetak
Osnovni cilj ovog rada jeste da pokaže prednosti i nedostatke vrednujući krutosti pri malim deformacijama nekoherentnog tla pomoću različitih tipova laboratorijske opreme. Serija konsolidacionih nedreniranih cikličkih triaksijalnih opita na uzorcima je peska iz Sofije i Tojoura, koji su imali različite gustine u suvom stanju. Relativno mali ciklusi rasterećenja i ponovnog opterećenja urađeni/izvedeni su na uzorcima s ciljem određivanja 'statičkog Jungovog modula'. Osim toga, korišćena su dva postupka prostiranja talasa radi određivanja 'dinamičkog Jungovog modula': jedan je korišćenje 'bender' link elemenata u poprečnom preseku uzorka, a drugi je korišćenje 'trigger' elemenata u podužnom preseku uzorka da bi se izazvali smičući talasi i dva akcelerograma koji hvataju/registruju dolazeće talase u dve tačke. U radu su analizirane razlike između ova dva tipa dinamičkog merenja i statičkog merenja, kao i zavisnosti između prethodno pomenutih pristupa.
Abstract
The main purpose of the presented paper is to show the advantages and disadvantages of evaluating the small strain stiffness of cohesionless soils by means of different types of laboratory equipment. A series of consolidated undrained cyclic triaxial testes have been performed on saturated specimens made of Toyoura sand and Sofia sand having various dry densities. Relatively small unloading-reloading cycles have been applied on the specimens in order to obtain the 'static' Young's modulus. Furthermore two types of wave propagation techniques have been adopted for the sake of a 'dynamic' Young's modulus determination: one is using bender elements in the cross section of the specimen and the other is using trigger elements in the longitudinal section of the specimen to excite shear waves and two accelerometers which capture the waves' arrival in two points. On one hand the difference between the two types of dynamic measurements and static measurements is discussed and on the other hand some relationships between the abovementioned approaches are given.
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