Geographically distributed hybrid testing & collaboration between geotechnical centrifuge and structures laboratories

Distributed Hybrid Testing（DHT） is an experimental technique designed to capitalise on advances in modern networking infrastructure to overcome traditional laboratory capacity limitations. By coupling the heterogeneous test apparatus and computational resources of geographically distributed laboratories, DHT provides the means to take on complex, multi-disciplinary challenges with new forms of communication and collaboration. To introduce the opportunity and practicability afforded by DHT, here an exemplar multi-site test is addressed in which a dedicated fibre network and suite of custom software is used to connect the geotechnical centrifuge at the University of Cambridge with a variety of structural dynamics loading apparatus at the University of Oxford and the University of Bristol. While centrifuge time-scaling prevents real-time rates of loading in this test, such experiments may be used to gain valuable insights into physical phenomena, test procedure and accuracy. These and other related experiments have led to the development of the real-time DHT technique and the creation of a flexible framework that aims to facilitate future distributed tests within the UK and beyond. As a further example, a real-time DHT experiment between structural labs using this framework for testing across the Internet is also presented.

Effect of biopolymers on permeability of sand-bentonite mixtures

Application of biopolymer-modified geomaterials in waste disposal practices is gaining wide acceptance due to their superior tensile characteristics and improved crack resistance.Permeability is an important design parameter which determines the suitability of a material as a liner for construction of engineered landfills.Given this,the permeability characteristics of sand-bentonite mixtures amended with biopolymers was studied using a modified-falling head permeability apparatus under an accelerated gravity environment.Both distilled water and synthetic leachate were utilized as permeant liquid to assess the role of biopolymer amendment on the permeation behavior of sand-bentonite mixtures.Experimental results indicate that addition of biopolymers causes aggregation of the clay platelets,which in turn enhances the permeation behavior of the biopolymer-modified sand-bentonite mixtures.These mixtures meet the regulatory requirement of the liner.

Centrifuge experiments for shallow tunnels at active reverse fault intersection

Tunnels extend in large stretches with continuous lengths of up to hundreds of kilometers which are vulnerable to faulting in earthquake-prone areas.Assessing the interaction of soil and tunnel at an intersection with an active fault during an earthquake can be a beneficial guideline for tunnel design engineers.Here,a series of 4 centrifuge tests are planned and tested on continuous tunnels.Dip-slip suface faulting in reverse mechanism of 60°is modeled by a fault simulator box in a quasi-static manner.Failure mechanism,progression and locations of damages to the tunnels are assessed through a gradual increase in Permanent Ground Displacement(PGD).The ground surface deformations and strains,fault surface trace,fault scarp and the sinkhole caused by fault movement are observed here.These ground surface deformations are major threats to stability,safety and serviceability of the structures.According to the observations,the modeled tunnels are vulnerable to reverse fault rupture and but the functionality loss is not abrupt,and the tunnel will be able to tolerate some fault displacements.By monitoring the progress of damage states by increasing PGD,the fragility curves corresponding to each damage state were plotted and interpreted in related figures.