Exploring the mechanisms of shear wave propagation in granular materials using DEM

Shear wave propagation and associated velocity Vs, are fundamental in characterising the small-strain response of soils. In addition, the shear wave velocity is essential input information in the characterisation of soils under static and dynamic conditions and eventually, in the design of geotechnical structures. 

The present study aims in exploring the mechanisms of wave propagation in dry and (ultimately) saturated granular materials on an interparticle level through the use of DEM. In particular, the first attempt to capture the problem with the use of DEM is going to be based on simple assumptions, which will gradually increase in complexity to incorporate more information with regards to the micro- and the macro- mechanics of the problem at hand, and link to actual soil conditions. The initial simulations will consist of cylindrical and/or cubical samples of granular materials, which will be subjected to a shearing excitation at one end. The shear wave velocity will be measured by means of the time required for the excitation to arrive at the other end of the specimen of known length. In this initial exercise, the granular material will consist of spherical smooth particles of standard size (single fraction in PSD curve terms). Dry conditions will be considered initially, and the effect of different levels of confining stress will be investigated. Depending on the associated computational time and numerical-related challenges (e.g., appropriate selection of boundary type, etc), the parametric investigation will be extended into considering the effects of particle shape, roughness (rough spherical particles), particle size (smaller and larger particles) and void ratio (loose and dense state) upon the magnitude of the shear wave velocity. 

The ultimate long-term purpose of the present work, which does not fall withing the scope of the present paper, is to continue increasing the complexity of the DEM simulations and expanding the research in order to fully understand wave propagation in granular materials. In particular, exploring how the shear wave velocity is affected under a liquefaction regime and identifying the controlling parameters in this condition is of interest. Being able to evaluate the shear wave velocity of the liquefied soil by means of DEM simulations and under various soil and excitation conditions is going to provide valuable insight into the behaviour of liquefied soils and allow us to potentially revisit some of the provisions of the existing design codes with regards to the considered shear wave velocity. 

Academic qualifications

A first-class honours degree, or a distinction at master level, or equivalent achievements in the following subject areas – Civil Engineering  

English language requirement

If your first language is not English, comply with the University requirements for research degree programmes in terms of English language.

Application process

Prospective applicants are encouraged to contact the supervisor, Dr Vasiliki Dimitriadi ([email protected]) to discuss the content of the project and the fit with their qualifications and skills before preparing an application. 

Contact details

Should you need more information, please email [email protected].

The application must include: 

Research project outline of 2 pages (list of references excluded). The outline may provide details about

• Background and motivation, explaining the importance of the project, should be supported also by relevant literature. You can also discuss the applications you expect for the project results.
• Research questions or
• Methodology: types of data to be used, approach to data collection, and data analysis methods.
• List of references

The outline must be created solely by the applicant. Supervisors can only offer general discussions about the project idea without providing any additional support.

• Statement no longer than 1 page describing your motivations and fit with the project.
• Recent and complete curriculum vitae. The curriculum must include a declaration regarding the English language qualifications of the candidate.
• Supporting documents will have to be submitted by successful candidates.
• Two academic references (but if you have been out of education for more than three years, you may submit one academic and one professional reference), on the form can be downloaded here.

Applications can be submitted here. To be considered, the application must use:

• the advertised title as project title 

Download a copy of the project details here