This work introduces a scaling analysis of sub-aerial axisymmetric column collapses of glass beads and Newtonian glycerol-water solutions mimicking some of the behaviours of debris flows. The beads were in a size range where their inertia partly decouples their collapse behaviour from the water column. Experiments explored a range of viscous, surface tension and particle inertia effects through systematic variation of particle size and fluid viscosity. Crucially a geotechnical centrifuge was used to access elevated effective gravitational accelerations driving the collapse, allowing field-scale viscous and surface tension effects to be replicated. Temporal pore pressure and run out front position evolution data was extracted using a pressure transducer and high speed imaging, respectively. A least-squares fitted scale analysis demonstrated that all characteristic dimensionless quantities of the acceleration phase could be described as a function of the column-scale Bond number $$\text{ Bo }$$ Bo , the Capillary number $$\text{ Ca }$$ Ca , the system size $$r^*$$ r ∗ , and the grain-fluid density ratio $$\rho ^*$$ ρ ∗ . This analysis demonstrated that collapses as characterised by pore pressure evolution and front positions were controlled by the ratio of $$\text{ Bo}/\text{Ca}$$ Bo / Ca . This indicates that grain-scale surface tension effects are negligible in such inertial column collapses where they may dominate laboratory-scale granular-fluid flow behaviour where geometric similarity between grain and system size is preserved. Graphical abstract

Geotechnical centrifuge models necessarily involve simplifications compared to the full-scale scenario under investigation. In particular, structural systems (e.g. buildings) generally cannot be replicated such that complex full-scale characteristics are obtained. Hybrid testing offers the ability to combine capabilities from physical and numerical modelling to overcome some of the experimental limitations. In this paper, the development of a coupled centrifuge-numerical model (CCNM) pseudo-dynamic hybrid test for the study of tunnel–building interaction is presented. The methodology takes advantage of the relative merits of centrifuge tests (modelling soil behaviour and soil–pile interactions) and numerical simulations (modelling building deformations and load redistribution), with pile load and displacement data being passed in real time between the two model domains. To appropriately model the full-scale scenario, a challenging force-controlled system was developed (the first of its kind for hybrid testing in a geotechnical centrifuge). The CCNM application can accommodate simple frame analyses as well as more rigorous and non-linear simulations using Abaqus. A novel data-exchange method between Abaqus and LabView is presented, which provides a significant enhancement compared with similar hybrid test developments. Data are provided from preliminary tests which highlight the capabilities of the system to accurately model the tunnel–building interaction problem.

Tsinidis, Grigorios and Pitilakis, Kyriazis and Madabhushi, Gopol and Heron, Charles (2015) Dynamic response of flexible square tunnels: centrifuge testing and validation of existing design methodologies. Geotechnique, 65 (5). pp. 401-417. ISSN 1751-7656 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/34819/1/2016%20-%20Tsinidis%20-%20Geotechnique%20-%20Dynamic%20Response%20of%20Flexible%20Square%20Tunnels%20Centrifuge %20Testing%20and%20Validation.pdf

A new macro-element model encapsulating the dynamic moment-rotation behaviour of raft foundations. Geotechnique, 65 (5). pp. 442-451. ISSN 1751-7656 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/34863/1/2015%20-%20Heron%20-%20Geotechnique%20-%20A%20new%20macro-element%20model%20encapsulating%20the%20dynamic %20moment-rotation%20behaviour%20of%20raft%20foundations.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractThe interaction of shallow foundations with the underlying soil during dynamic loading can have both positive and negative effects on the behaviour of the superstructure. Although the negative impacts are generally considered within design codes, seldom is design performed in such a way as to maximise the potential beneficial characteristics. This is, in part due to the complexity of modelling the soil-structure interaction. Using the data from dynamic centrifuge testing of raft foundations on dry sand, a simple moment-rotation macro-element model has been developed which has been calibrated and validated against the experimental data. For the prototype tested, the model is capable of accurately predicting the underlying moment-rotation backbone shape and energy dissipation during cyclic loading. Utilising this model within a finite element model of the structure could potentially allow a coupled analysis of the full soil-foundation-structure system's seismic response in a simplified manner compared to other methods proposed in literature. This permits the beneficial soil-structure interaction characteristics, such as the dissipation of seismic energy, to be reliably included in the design process resulting in more efficient, cost-effective and safe designs.In this paper the derivation of the model will be presented including details of the calibration process. In addition, an appraisal of the likely resultant error of the model prediction will be presented and visual examples of how well the model mimics the experimental data will be

Tsinidis, Grigorios and Pitilakis, Kyriazis and Madabhushi, Gopol and Heron, Charles (2015) Dynamic response of flexible square tunnels: centrifuge testing and validation of existing design methodologies. Geotechnique, 65 (5). pp. 401-417. ISSN 1751-7656 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/34819/1/2016%20-%20Tsinidis%20-%20Geotechnique%20-%20Dynamic%20Response%20of%20Flexible%20Square%20Tunnels%20Centrifuge %20Testing%20and%20Validation.pdf