Assessment of Design Alternation via 2D Physical Modelling in the Main Breakwater of Colombo Port Expansion Project

Abstract

Colombo Port Expansion Project was initiated with the recognition of increment in demand for container throughput in future. Construction works of the project are in progress. The toe of the main breakwater contains 8 - 12 T large boulders. Whilst the construction of main breakwater is in progress, contractor faced difficulties to find the 8 - 12T rock boulders from queries for toe. Hence, application of 20 T CORE-LOC instead of 8-12T was proposed by the contractor. Two dimensional (2D) physical model testing was carried out to assess the stability of toe in main breakwater with two or three CORE-LOC (20T) rows instead of 8 - 12T boulders. Model scale was determined considering flume dimensions, sea bed profile, available CORE-LOC miniatures and wave heights to be tested and dimensions of the breakwater section etc. Scaling down of the prototype to model was done according to the Froude’s Similarity and model units (armour units, CORE-LOC) were scaled down based on Hudson’s Stability Criterion. Several alternative design sections were subjected to the testing and higher emphasis was set to maintain the specified rock gradations. Study determined the adequate number of CORE-LOC rows to replace the existing 8 - 12T large boulders layers while considering overall stability of the breakwater.

Keywords

CORE-LOC, Froude’s Similarity, Hudson’s Stability Criterion, Model Scale