FAILURE OF SEABEDS WITH A HIGH MUD CONTENT: AN EXPERIMENTAL STUDY

Abstract

Seabed instability has been cited as the cause of failure for a number of coastal structures in recent years, stimulating an interest in understanding the interaction between waves, marine structures and the seabed upon which they are built. A series of experimental tests were carried out in a wave flume at the Engineering Institute of the National University of Mexico, to investigate the failure of seabeds with a high mud content and the interaction of the seabed with a scaled structure (vertical breakwater) and regular waves (T = 0.6, 0.8 and 1.0 s; H = 6, 8 and 10 cm), through the analysis of pore pressure distribution. Three different materials were tested: 100, 90 and 85 % mud content, mixed with natural sand and water. Pore pressure build-up was registered in the tests with 85 % of mud content, and knowing that a build-up precedes soil liquefaction, failure may have occurred. But in these cases the maximum pressure in the tests did not exceed the critical value and no liquefaction was observed. For soils of 90 and 100 % mud content, the pore pressure shows a homogeneous vertical behaviour and only pore pressure falls were registered. This phenomenon may be attributed to the cohesion effect in the mud particles and to the consolidation process.