Asymptotic behaviour of sand in plane-strain compression tests

• Autorzy: Wanatowski, D.

Warianty tytułu

PL

Asymptotyczne zachowanie się piasku w płaskim stanie odkształcenia podczas próby ściskania

• Języki publikacji: EN

Abstrakty

EN

Experimental data are presented, which allows the asymptotic behaviour of sand under plane-strain conditions to be studied. K0 consolidated plane-strain tests were conducted using a new plane-strain apparatus under strain path-controlled conditions. The stress-strain behaviour of sand in very loose and medium dense states undcr plane-strain conditions was characterized. The results show that thc strcss-strain behaviour of sand under plane-strain conditions is strain path-dependent. When the strain incremcnt ratio imposed on specimens (dEv/dEl)i; is higher (i.e., more positivc) than a threshold value, strain hardening behaviour will prevail. On the other hand, when the(dEv/dEl)i is lower (i.e., more negative) than a threshold value, strain softening will occur. The threshold strain increment ratio is defined as (dEv/dEl)i, that is the strain increment ratio at failure as measured in a drained test. It is also observed that the asymptotic behaviour of sand cannot be predicted by the Cam clay moclels or the Rowe's stress-dilatancy equation. This is consistent with the observations made by other rcsearchcrs undcr axisymmetric conditions.

PL

Przedstawione dane doświadczalne umożliwiają badanie asymptotycznego zachowania się piasku w warunkach płaskiego stanu odkształcenia. Badania przeprowadzono w warunkach kontrolowanego płaskiego stanu odkształcenia z konsolidacją w jednoosiowym stanie odkształcenia, korzystając z nowo zaprojektowanego aparatu dwuosiowego ściskania. Scharakteryzowano zależności pomiędzy naprężeniami i odkształceniami dla piasku w stanie luźnym i średnio zagęszczonym. Otrzymane wyniki świadczą, że zależności między naprężeniami i odkształceniami próbek piasku w warunkach płaskiego stanu odkształcenia zależą od kontrolowanej ścieżki naprężeń. Jeśli współczynnik przyrostu odkształcania (dEv/dEl)i któremu poddano próbki, przekracza wartość graniczną (tzn. jest bardziej dodatni), to próbki ulegają wzmocnieniu. Jeśli zaś wartość tego współczynnika jest niższa od wartości granicznej (tzn. jest bardziej ujemna), to próbki ulęgają osłabieniu. Graniczny współczynnik przyrostu odkształcenia jest zdefiniowany jako (dEv/dEl)i tjźwspółczynnik przyrostu odkształcenia zmierzony w momencie ścięcia próbki w badaniu wytrzymałościowym metodą ścinania powołanego z odpływem wody. Na podstawie przeprowadzonych badań stwierdzono również, że asymptotycznego zachowania się piasku nie można przewidzieć ani opierając się na modelach gliny Cam, atli na równaniu Rowe'a opisującym zależność naprężenia od dylatacji. Jest to zgodne z obserwacjami poczynionymi przez innych badaczy w warunkach symetrii osiowej.

Słowa kluczowe

PL

piasek; próba ściskania

EN

sand; campression test; plane strain

• Czasopismo: Studia Geotechnica et Mechanica
• Rocznik: 2007
• Tom: Vol. 29, nr 3-4
• Strony: 19-44
• Opis fizyczny: bibliogr. 41 poz.

Twórcy

autor

Wanatowski, D.

• Lecturer, Nottingham Centre for Geomechanics, School of Civil Engineering

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