Micromechanics of soils

The soil can be considered as a collection of grains or aggregates with microstructures, aggregates are composed of particles with interparticle voids, and grains or particles are made of minerals with atomic structures. Thus, the origin of mechanical behaviours/properties of the soil can be investigated by downscaling, and the mechanical modelling of the soil can be conducted by upscaling.

Time-dependency of soft soils

Natural soft clays exhibit several features: (a) significant anisotropy developed during their deposition, sedimentation, consolidation history and any subsequent straining; (b) some apparent bonding which will be progressively lost during straining; and (c) time-dependent stress-strain behaviour which has a significant influence on the shear strength and the pre-consolidation pressure. Since all these features cannot be neglected, in the modelling we considered all above features. The application of the proposed model ANICREEP requires the same experimental information as needed for the Modified Cam Clay model, which makes the model attractive for geotechnical practice.

Grading-dependency of granular soils

Mechanical properties/behaviours are significantly affected by the grain size distribution of the granular soil, which is called “grading-dependency”. The grading change can be induced by grain breakage. Bigger sized grains are easier to be crushed. If the soil is gap-graded, the change of fines content can be induced by seepage force so-called suffusion/internal erosion. Currently, we focuses on how the soil grading evolves, what is mechanical consequence, and how to model the full coupling for engineering design.

SSI in Marine Geotechnics

Soil–structure interaction (SSI) consists of the interaction between soil (ground) and a structure built upon it, in which the foundation structures with their surrounding soils (in certain range which soil is disturbed) can be regarded as an entire system, so-called a macro-element, with global forces (or moments)-displacements (or rotations) responses. Currently, we focused on the design of caisson foundation by means of discrete element method, finite element method and mesh-free method for progressive failure analysis and failure envelope investigation, which have been later applied to establish “forces-displacements” models in structural level so-called macro-element models.

Practice of AI in Geotechnics

We have extensively performed the application of AI in geotechnics due to the strong capacity of solving non-linear and high-dimensional problem of AI. For example, the optimization and Bayesian-based methods can bridge the gap between advanced constitutive theories and engineering practice; ML-based surrogate model can also be applied in engineering practice as the alternative to experimental and numerical methods, saving expenses for engineering design. Currently, we focuses on the following four topics.

Large Deformation Analysis in Geotechnics

In geotechnical engineering, numerous problems involve large deformation, such as installation of foundations, tunnel face instability, landslides, etc.. Benefitted from the sustained development of computing power, numerical simulations have become standard methods in geomechanics and its related fields. Adequate simulations with large deformation analysis are helpful for geotechnical design and disaster protection.

Development of model tests

Hong Kong faces the severe scarcity of construction land. Hong Kong government approved a reclamation project namely Lantau Tomorrow vision to meet the increasing demand for housing. To reduce the expense of filling material and the environmental impact, sometimes the marine clays on the neighboring seabed would be used as filling material. However, the marine clay has high water content, low permeability and high compressibility. Another problem is that there are two stages during a whole reclamation process: sedimentation and consolidation. Traditional research focuses on primary consolidation only.