PORT WORKS DESIGN MANUAL PART 5 Guide to Design of ...
PORT WORKS DESIGN MANUAL PART 5 Guide to Design of ...
PORT WORKS DESIGN MANUAL PART 5 Guide to Design of ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
31<br />
5. <strong>DESIGN</strong> METHODOLOGY<br />
5.1 General<br />
This chapter gives guidance on the estimation <strong>of</strong> beach dimensions, assessment <strong>of</strong> fill<br />
stability and design <strong>of</strong> sand retaining structures. It should be noted that the processes in<br />
nature which cause reshaping <strong>of</strong> the beach fill are complex, and quantitative formulation <strong>of</strong><br />
such deformations available nowadays are still not very accurate. Hence, the computations<br />
can only yield approximate figures. It is worthwhile <strong>to</strong> investigate the performance <strong>of</strong><br />
previous beach nourishment schemes under similar site conditions for reference in design.<br />
5.2 Fill Quantity<br />
Several analytical methods <strong>to</strong> estimate the fill quantity are given (CIRIA, 1996) for<br />
preliminary design purpose. These methods take in<strong>to</strong> account the reshaping <strong>of</strong> beach pr<strong>of</strong>ile<br />
and sediment losses. However, none <strong>of</strong> these methods should be used in isolation. Instead,<br />
they should be used <strong>to</strong>gether <strong>to</strong> indicate the potential range <strong>of</strong> fill volumes. General<br />
descriptions <strong>of</strong> the principles <strong>of</strong> these methods are given in the following paragraphs and<br />
details <strong>of</strong> the formulae are described in Appendix A. The estimated fill quantity may be<br />
used as a starting point <strong>of</strong> determining the construction pr<strong>of</strong>ile and equilibrium pr<strong>of</strong>ile <strong>of</strong> the<br />
beach. A worked example is given in Appendix B <strong>to</strong> illustrate the use <strong>of</strong> these methods.<br />
It should be noted that loss <strong>of</strong> fill may occur due <strong>to</strong> actions <strong>of</strong> waves and currents during fill<br />
placement. The actual fill quantity required may be more than the quantity estimated by<br />
these methods.<br />
5.2.1 Equilibrium Pr<strong>of</strong>ile Method<br />
Dean’s equilibrium pr<strong>of</strong>ile method (see Section A.2 <strong>of</strong> Appendix A) estimates the fill volume<br />
<strong>of</strong> a given grain size <strong>to</strong> produce a desired width <strong>of</strong> beach per unit length <strong>of</strong> the shoreline after<br />
the pr<strong>of</strong>ile has reached equilibrium. This method considers three types <strong>of</strong> nourished pr<strong>of</strong>ile<br />
that depends on the size <strong>of</strong> the fill and native beach sediment. Having determined the type<br />
<strong>of</strong> nourished pr<strong>of</strong>ile by means <strong>of</strong> the Dean formulae, the volume <strong>of</strong> fill can be calculated from<br />
the formulae given in the method.