The mechanism of inhibiting swelling deformation and slope instability of expansive soils by replacement method

Za padine od ekspanzivnih tala, zamjena glinom koja ne nabrekne je uvijek najučinkovitija mjera. Ipak, još uvijek postoje neriješeni problemi u načinu zamjene, uključujući kako odrediti optimalnu debljinu zamjene i da li dolazi do nestabilnosti padina ekspanzivnih tala. U ovom je radu primijenjen "Stress Path Triaxial Testing System" (GDS) za istraživanje troosnog omjera izdizanja. Predložen je troosni model omjera izdizanja za ekspanzivna tla i taj je model razvijen u ABAQUSu. Nanesena je zamjenska glina različite debljine pri ispitivanju padina sastavljenih od čvrstog, srednjeg i slabog ekspanzivnog tla. Provedena je i analiza osjetljivosti primjenom metode konačnih elemenata. Za padinu od čvrstog ekspanzivnog tla s prirodnim sadržajem vlage od 27,5 % faktor sigurnosti bez zamjene glinom bio je 0,73. Faktor sigurnosti bio je 0,85; 1,08 i 1,33 uz odgovarajuću debljinu zamjene od 1 m, 2 m i 3 m. Rezultati su potvrdili da se metodom zamjene može ne samo spriječiti izdizanje ekspanzivnih tala već se može i odgovarajuće poboljšati stabilnost padine. Uz to, različitim debljinama zamjene mogu se postići različiti omjeri povećanja faktora sigurnosti padine. Rastući omjer se nelinearno promijenio. Konačno, pokazan je mehanički mehanizam učinaka smanjenja metodom zamjene na nestabilnost padine od ekspanzivnog tla. Rezultati istraživanja mogu pružiti teoretsku osnovu za praktično inženjerstvo u tretiranju opasnosti od izdizanja kod padina od ekspanzivnog tla.For expansive soils slope, replacement with non-swelling clay is always the most vital treatment measure. However, there are still many unsolved problems in the replacement method, including how to determine the optimal replacement thickness, and whether there was inhibition effect on slope instability of expansive soils. In this study, a "Stress Path Triaxial Testing System" (GDS) has been applied for exploring triaxial swelling rate. It proposed a triaxial swelling rate model for expansive soils, and this model was secondary developed and embedded in ABAQUS. Different thicknesses of replacement clay have been applied in treating slopes composed by strong, medium and weak expansive soil respectively. Sensitivity analysis also has been carried out with finite element method. For the strong expansive soil slope with natural moisture content 27,5 %, the safety coefficient without clay replacement was 0,73. The safety coefficient was 0,85; 1,08 and 1,33 with the replacement thickness of 1 m, 2 m and 3 m, respectively. The results validated that the replacement method could not only effectively inhibit the swelling of expansive soils, but also correspondingly improve the slope stability. In addition, the different replacement thicknesses could bring varied increasing rate of slope safety coefficient. The increasing rate was nonlinearly changed. Finally, it demonstrated the mechanical mechanism of inhibiting effects from existing replacement method on slope instability of expansive soils. The research results are able to provide theoretical basis for practical engineering. It could be conductive to treating swelling danger from expansive soil slope