Centrifuge study of the mechanisms of rubble mounds sinking into soft clay seabeds in the construction stage

Abstract

The construction of a rubble mound breakwater over a soft clayey seabed is a challenging issue in marine engineering. Excessive settlement and the sinking of such structures into the seabed sludge impose high costs on a project and can cause operational problems. The present study evaluated the mechanisms contributing to the large deformation that can occur during the construction of a breakwater using the results of four centrifuge tests. The result showed that the penetration of individual pieces of rubble and the flow of soft clay into the rubble pores were the leading mechanisms contributing to material loss during the construction of the breakwater. According to the conducted tests, the amount of material loss contributing to the penetration of individual rock particles for Cu = 3.2, 4.1, 11.2 kPa, equal 10.3, 7.6 and 2% of the initial breakwater section respectively. Also, the amount of material loss caused by the flow of sludge into rock pores for the three mentioned undrained shear strengths are equal to 15.1, 10.4 and 5.9% of the initial section respectively. So current study indicates that failing to account for these two mechanisms can lead to considerable underestimation of the required material for construction.