197_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

197_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 -...

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SL23 Critical Slip Surface - Minimum Factor 01 Safety a Analysis of circular faHure surfaces must be repeated for different circles until the-critical lip sudace is found, i.e~the:slip surface with the smallest factor ofsafety. a First choose a radius value or fix a starting point for the slip circle (say the toe). o Then develop a contour map, using a grid, which shows the calculated safety factor for each slip circle plotted at the circle center (similar to an elevation contour plot) o Identify zone of minimum safety factor from FS contours. Moment axis "b" (FS '" 1.5 lor momont aXiS\"b") Moment axis "a" • ., (FS = 1.1 for momont rb •••• \....... ' IDeIS "a") ~ C:;-~~'""T''''-','~' "'"" ... ~ .' , . , , \ :"a . , , . , . .. .. " , Slip surface fO( moment axis "a" Most critical slip surface (least FS) , . . , , . Moment axis for slip surface having least FS (a) location of moment axis arlecls FS (b) Use of grid 10 establish FS contours to help Iocato most critical slip surface
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Unformatted text preview: Sand Drain Effects of moment axis location on calculated factor of safety and melhod to establish mOst critical slip surface. o Choose another radius or staring point and repeat the FS contour map. o From a series of FS contour maps, identify a critical zone where FS is minimal. o Calculate the minimum safety factor for a slip circle centered in this critical zone. Typically require FSmin = 1.5. o Computer programs use a search technique to locate the critical zone. Water Pressure by Flow Nets (use with method of slices) o Draw slope to scale and divide into slices o Construct tlow net with tlow lines and equipotential lines (they are perpendicular) ~-.. \ . ..... '/- FlowLines .. "(. . \ f .. \ \ \..-~ __ J,--~ Equipotential Lines , ,/1/1'_ ~~::;;'0>;r};;N;:~;.: l I I __ .J - - -----_.--_ ..----...
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This note was uploaded on 02/10/2012 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.

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