PORT WORKS DESIGN MANUAL PART 3 Guide To - The University ...

31requires checking of the equilibrium of the soil mass along a sufhciei:i Briber of arbitrarilyselected failure surfaces to find the minimum value of the factor of safety for eachreclamation stage.The principle of method is illustrated in Figure 5.selected failure surface Is defined by:The factor of safety associated with theF = - — (3.2)where R = Moment arm for r f .T f = Shear strength along the selected surface./ = Length of vertical slices along the selected surface.W = Weight of vertical slices.x - Moment arm for W.The slip surface in Figure 5 is for illustration only. Designers should consider all possibleslip surfaces, either circular or non-circular ones, in the analysis. Stability analysis isusually performed using a computer program. Several are available in the market.3.2 Drained Reclamation3.2.1 Stability during ConstructionThe stability of a reclamation during filling is particularly important where the underlyingsoft marine and alluvial deposits are left in place. Improper placement of fill on such soilcould lead to failure and have significant programming, financial and life consequences.Therefore, any proposed reclamation methodology and sequence, as well as subsequentchanges, must be subject to stability analysis before it is executed. Fill placement inshallow water onto thick marine mud is likely to cause mud wave formation unless it iscarried out carefully, and stability at each interim construction stage should be checkedduring the design phase.(1) Simplified Analysis Method for Short-term StabilityThe simplified stability analysis method described in this section may be used to provide aquick preliminary assessment of the stability of the leading edge of the reclamation.