Centrifuge modelling of wave-induced seabed response in clay

This paper describes a programme of centrifuge tests on the behaviour of clayey seabed under wave loading using an in-flight wave loading system. Three model seabeds of kaolin clay capturing typical un-consolidated, normally-consolidated and over-consolidated soil responses, were considered; and each seabed experienced several episodes of wave loading and resting. Data acquisition measures included pore pressure transducers, accelerometer, bender elements and T-bar penetrometers. The depth-wise distribution of excess pore pressure, soil strength and modulus, as well as the motion of liquefied layer of seabed, was monitored throughout to enable a thorough investigation into the liquefaction and reconsolidation feature of the soil. For the un- and normally-consolidated soils, remarkable development of residual pore pressure was observed, and there was evidence that strength/modulus recovery cannot be achieved by the surficial soil within a prototype time of 15 days. Within a certain depth below this surficial layer, there was drastic increase in undrained strength, and this phenomenon was carefully examined by a modified moving-boundary model. For the over-consolidated soil, build-up of residual pore pressure was rather limited but discernible amplification of oscillatory pore pressure amplitude was observed. Implications for practice in offshore engineering were then discussed based on the experimental findings.