The Geotechnical Group group has been active in geotechnical research since 1994. In its current form it maintains a strong focus in the fields of numerical modelling and the laboratory testing of unsaturated soils. Its current main work themes are:
Unsaturated soils (i.e. soils whose voids contain both water and air) are at the forefront of current geotechnical and geoenvironmental engineering research, as they are linked to a number of topical problems. For example, waste disposal facilities, flood dikes and dams, mudflows and slope failures, cyclic changes in soil properties due to extreme climatic changes, swelling and collapse of soils/fills, CO2 storage. Testing techniques for unsaturated soils are not trivial and appropriate constitutive models (to be used for the numerical modelling of such soils) are the focus of continuous research and development worldwide
The group has been involved in a number of projects on unsaturated soils and associated PhD studies since 1995. This has resulted into the pioneering development of state of the art experimental apparatus. Amongst other activities the group is currently working on the constitutive modelling of unsaturated soils and the development of numerical software tools that can model and predict the behaviour of this type of soil in a variety of situations and engineering problems, and the development of an improved volume change measurement tool for unsaturated soil testing.
Chemical treatment of soils is an attractive technique of ground improvement as it allows the use of "in situ" soils without the need to remove and replace unsuitable soil material. This saves in construction time and costs (including landfill taxes) and reduces emissions from vehicles. It therefore emerges as a more sustainable alternative to exporting and landfilling unsuitable in situ soil, and replacing it by imported, more suitable fill. For this reason such techniques are now increasingly considered for a wider range of civil engineering applications than those originally suggested.
The need has therefore emerged for predictive numerical tools able to describe the behaviour of chemically treated soils for a variety of problems. Such engineering tools are not available at the moment for this type of soil. Current EPSRC-funded research undertaken by the group aims at developing such a predictive tool based on new experimental data on lime-treated UK clay soils. Specifically the strength of the soil in drained conditions, the stiffness (including investigation of the yielding characteristics), the permeability and water retention characteristics are measured.
An additional novelty of the research is that lime-treated soils under both saturated and unsaturated conditions are tested using suction-controlled triaxial apparatus. Moreover, the experimental results are interpreted using an especially formulated novel constitutive model for cemented saturated and unsaturated soils. The outcome of the research is the implementation of the constitutive model into commercial Finite Element software, to provide engineers with analytical tools able to model the behaviour of chemically treated (cemented) soils in a variety of civil engineering applications. Future research of the group aims at applying the experimental and numerical tools for research on biologically treated soils.
Most geotechnical applications involve to one extent or another interaction between the soil and civil engineering structures. The analysis of such type of problems, both existing and at design stage is complex and necessitates the development of sophisticated numerical tools.
Led by Prof MJ Gunn, the group has carried out a number of research and consultancy projects in the area of the numerical modelling of soil-structure interaction problems (including tunnelling, retaining walls and building foundation subject to static and dynamic loading), many of which were related to now completed PhD studies. Current EPSRC-funded research in the field addresses the adequate assessment of the long-term stability of historic London Underground retaining structures.
In addition to standard geotechnical testing apparatus (shear boxes, ring-shear, standard triaxial testing systems, permeameters, standard oedometer/Rowe cell devices) the group benefits from unsaturated soil testing facilities (three fully equipped stress path triaxial testing systems and pressure plate apparatus) automated using TRIAX and GDSLab software.
Members of the geotechnics group have also been involved in the continuous improvement and development of novel experimental tools for soil testing. We use and further develop state-of-the art geotechnical modelling software. This includes mainly the geotechnical program CRISP, whose original co-author is Prof M.J Gunn, as well as the commercial Finite Element program ABAQUS. Members of the group have also developed other own simulation models and techniques for unsaturated soil modelling (e.g. FUSS: Flow in Unsaturated-Saturated Soils).
Throughout our research we have been liaising with a number of companies (e.g. GDS Ltd, Metronet, GCG, Jacobs) and academics from other UK groups. The team welcomes any opportunity for academic/industrial collaboration including multidisciplinary research networks, Knowledge Transfer Partnerships and consultancy activities.
The group is currently involved in two EPSRC-funded projects with a total grant funding of approximately £310,000.
Dr Maria Mavroulidou
Tel: 020 7815 7646
Email: mavroum@lsbu.ac.uk
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