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- 133-WMLTYPELOAD DIAGRAMSTABILITY CRITERIASLIDINGS - (W t + P vFs (sliding)tan>1.5a:oi.e. F.S. on any included ultimate passive > 3.0OVERTURNINGmMoments about the toe of the baseFs (overturning) • Homents Desisting overturning m MrMoments causing overturning Mo Hr*io•4->Oa:oLU>LU OLU 'VERTICALSTEMRANKINECASERANKfNECASEMr * W t aMo *Fs »H.8.W t a(Passive ResistancePp ignored)>2.0it is illogical to take vertical componentsof the disturbing forces and usethem as restoring moments in theexpression for F.S. See section 6,3.2Overturning may be ignored if R w lies withinmiddle third (soil), middle half (rock).For gravity type walls, overturning must bechecked at selected horizontal planes, theresultant must remain within the rriddlethird.LOCATION OF RESULTANTPoint where R w intersects base, from toe,W t a + P v f - PHy * U 1V C - U 1H d - U 2 eh * W t + P v + ^1V " U 2(Passive resistance Pp ignored)For soil foundation material, R w shouldwithin middle third of the baselieFor a rock foundation, R w should He withinmiddle half of the baseBEARING PRESSURESee section 6.4 for Calculation of factor ofsafety for bearing Fs (bearing) 3-0Wt = total weight of the wall including soilon toe plus soil above heel (forcantilever walls only)resultant of W tf 1*2SLOPE FAILURE SN SURROUNDING SOILWith shear surfaces passing under the wall,the factors of safety should comply withthe requirements of Table 5*2 of theGeotechnical Manual for Slopes.•z< oOWATER FORCESReference should be made to Chapter 5 forcases other than those shown here*STABILITY CRITERIA FOR RETAINING WALLS [FIGURE 22