Pile penetration and loadings modelled by the Discrete Element Method
Dr (Helen) Yi Pik CHENG is Associate professor in soil mechanics at UCL. Before her appointment at UCL, Helen received his PhD at the Cambridge University about the micromechanical investigation on soil plasticity affected by particle crushing, under the supervision of Prof. Malcolm Bolton (Fellow of the Royal Academy of Engineering). Helen has currently mentored 19 PhD students and researchers (8 at UCL) and has published more than 60 journal and conference articles, including a few in the International Journal of Geotehnique. Her i10-index is 23 (h-index is 16) from Google scholar. She has served in the advisory panels including the journal of Getechnique, Geotechnique Letters, and also as guest editor in the journal of Computers and Geotechnics. She is also a member of the International Committee of TC105 Geo-mechanics from Micro to Macro. Helen’s research interests are on applications of the Discrete Element Methods in various geotechnical problems to understand the micro-mechanisms of soil systems, e.g. crushable soil mechanics, transitional soils, sand-silt soil mixtures, soil liquefaction, pile foundation and installations, and mechanical behaviour of methane hydrate bearing soils, soil reinforcement, and also sustainable applications such as the uses of waste tyres, recycled crushed glass and soilbags etc.
With a rising demand for renewable, sustainable and green energy sources, offshore wind industry is experiencing a rapid expansion. The most common type of support structure for offshore wind turbines are large-diameter monopiles. With this initial motivation in mind, a model pile was carefully created using the two-dimensional discrete element method. This numerical method is capable of modelling large strain particles movement around the pile. The grid method with an increased level of gravity was proposed in order to successfully and efficiently reproduce the uniformly increasing stresses ground condition of the granular sand.
The behaviour of pile penetration was then investigated, revealing the inter-relationship between volume change of the granular mass, the horizontal stress reversal and the friction degradation at pile shaft at different relative distance from the pile tip. After pile installation, the subsequent axial loading behaviour was also investigated, in which the distinct behaviour of different pile types will be highlighted. The monotonic horizontal loading simulations data matched well with a set of published centrifuge experimental data, showing non-linear load-displacement responses of the pile. Further investigations on the cyclic horizontal loadings will be also shown and explained.