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Diplomsko delo obravnava laboratorijske preiskave nesaturiranih zemljin s poudarkom preiskovanja fenomena sukcije. Sukcija je merilo za energijo, ki v strukturo zemljine privlači vodo ali jo tam zadržuje. V geotehniki sukcijo merimo s pomočjo različnih metod, kjer nas zanimajo predvsem vrednosti matrične sukcije. Meritve sukcije so bile opravljene v Geomehanskem laboratoriju Zavoda za gradbeništvo Slovenije, kjer smo sukcijo merili s pomočjo Bishop-Wesley dvostenske triosne celice in s potenciometrom, z namenom določanja retencijske krivulje v fazi sušenja vzorcev. Preiskave so potekale na dveh različnih materialih: trdnih peščeno meljnih zemljinah in na vzorcih mulja. Trdni melji so pri gradnji v slovenskem prostoru prisotni izjemoma in zato v geotehničnem smislu deležni obsežnejših preiskav. Veliko skrb predstavlja spreminjanje trdnostnih lastnosti v odvisnosti od zasičenosti, saj so v primeru, ko so izpostavljeni močenju ali obremenitvam, podvrženi porušitvam (kolapsu). Na izbranih vzorcih so bile najprej izvedene osnovne klasifikacijske preiskave: sejalne analize, meritve vlažnosti in gostote. Poleg merjenja sukcije v fazi sušenja smo meritve sukcije izvedli tudi v fazi vlaženja zemljine. Izdelava retencijskih krivulj temelji na podlagi uporabe različnih matemačnih modelov za opis retencijskih krivulj. Dobljene krivulje smo primerjali med preiskovanimi zemljinami in med uporabljenimi modeli ter opazovali, kateri model se izmerjenim vrednostim najbolje približa. Rezultati so pokazali dobro prileganje retencijskih krivulj izmerjenim vrednostim in ujemanje izmerjenih vrednosti sukcije z že znami rezultati iz literature. The thesis deals with laboratory testing of unsaturated soils, with an emphasis on investigation of soil suction phenomenon. Soil suction is referred to as the free energy state of soil water. In geotechnics suction is measured using a variety of methods, with the chief interest in the values of matrix suction. At the Slovenian National Building and Civil Engineering Institute suction was measured using Bishop-Wesley doublewall triaxial cell apparatus and dew point potentiometer, where the measurements were carried out in order to determine soil water characteristic curve in the phase of drying samples. Research was performed on two different types of materials: very stiff sandy silt and on samples of silty clay. Very stiff silt is very rare at construction sites in Slovenia and such areas therefore receive extensive geotechnical research. Especially worrying is the change in strength properties in relation to saturation, since they are prone to crushing or collapse when wet or overloaded. Selected samples were first subject to basic soil classification tests: sieve analysis, measurements of humidity and bulk density. In addition to the measurement of suction in the drying phase, suction measurements were also carried out at the stage soil moistening. Soil water characteristic curve was based on the use of different mathematical models to describe retention curves. The resulting curves were compared to the trial earths and the models used in order to determine which model fits best the measured values. The results showed good fit of retention curves to measured values. Our results also corresponded to the measured values of suction in other research papers and scholarly articles. |
