Elmira Khaksar Najafi - Geotechnical Engineer Ayandegan Institute of Higher Education Iran-Mazandaran

long-term stability of slopes in clay is an importantand challenging aspect of civil engineering. Determining of mainreason for instability is the first step to control the slopeinstability which can threat the performance of roads, railways,bridges, canals and so forth. Among different reasons ofinstability in clay excavations, delayed failure caused by softeningis the most important factor because of its destructive effectsafter passing some years on apparently stable slopes. Thus, inthis research, in addition to introduce delayed failurephenomenon, some examples damaged by this factor have beenmentioned, after that for more details fundamental reason of alandslide in a canal has been investigated in a case study. For thisreason, numerical study using Geo-Slope software has been doneto determine stability coefficient of cutting in two sides of canal.Finally, numerical analysis and available evidences showed theimportant factor for instability in one side of canal was related todelayed failure after passing more than forty years.

slope stability; negative pore pressure; canal; stiff clay; numerical study