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

53Ye et al (1997), the data set Ah, A8 H and h can be used to estimate the maximum allowableheight of fill. There is a consistent relationship between Ah/A8 H and h as shown inFigure 13. When h is small, Ah/AS H is large. As h gets larger, the relationship betweenAh/AS H and h will tend to become linear. If this straight portion is projected towards the h-axis, the intercept will give the predicted maximum height of filling. The height of fillshould not exceed this value until after consolidation of the mud layer (checked bymonitoring pore pressures).5.3.3 Verification of Settlement Based on Field Monitoring DataThe principle of verification of settlement involves back-analysis of field monitoring data.This can be carried out by fitting different values of coefficient of consolidation (vertical andhorizontal) into the consolidation equations and comparing the resultant settlement-timerelationships with the actual settlement-time curve plotted from field settlement data. BothTerzaghi's one-dimensional consolidation theory and Barren's radial consolidation theory forvertical and horizontal drainage respectively can be applied in the back-analysis (seeAppendix B). The process of curve fitting is a trial and error process which can be speededup with the use of computer programmes incorporating the appropriate consolidationequations and assumptions. Wai and Lam (2001) may be referred to for more details ofback-analysis by curve fitting.Alternatively, a method developed by Asaoka (1978) also enables utilization of the settlementmonitoring data, through simple graphical means, to verify the settlement due to primaryconsolidation calculated in the design stage. The principles and details of application of themethod are given in Appendix C. The results provide additional information for thedesigner to assess the settlement condition of the reclamation.Asaoka's method is based on observational settlement prediction. Field settlement datameasured by settlement plates at the seabed or, if not practicable, at the surface of thedrainage blanket, are plotted in accordance with the method given in Appendix C. Theplotted results give an estimate of total primary consolidation settlement of the soil beneaththe seabed, which can then be compared with the total primary consolidation settlementpredicted at the design stage. The residual settlement can also be re-assessed with referenceto the ultimate primary consolidation settlement estimated from Asaoka's Method and thefield settlement data measured at a particular time, say, at the time of completion of fillingworks or handing over the site.Asaoka's method has the advantage that it is simple to use.However, it relies very much on