Seminar - Anirban De - Use of a Geotechnical Centrifuge to Study the Effects of Surface Explosions

Wednesday 19 August 2009, 1.10 pm - 1.55 pm
Civil Engineering Lecture Theatre 3

The School of Civil Engineering is pleased to welcome Anirban De, from Manhattan College, NY, USA.

Abstract:
Explosions on the ground surface have the potential of causing significant damage to structures located on or close to the ground surface. Such structures may include earth dams and levees as well as underground tunnels and pipelines. The extremely transient nature of a blast load, coupled with the mechanism of crater formation and transfer of a blast excitation through soil, makes it a challenging task to model such events. Physical model tests involving full-scale explosions are expensive and pose significant risks. Numerical models must be calibrated against actual observations before their results can be used in practice.

Centrifuge model testing offers a unique opportunity to study soil-structure interaction phenomena using reduced scale physical models. A relatively small mass of explosives can be used under a high gravity, to model the same effects as produced under normal gravity when a much larger quantity of explosives is used. Results from centrifuge model tests on earth embankments and underground tunnels will be presented and discussed.

The tests on earth embankments investigated the effectiveness of a surface blast located on the crest of a dam in causing a breach. The tests on underground tunnels investigated the levels of strain that a surface blast could induce on a tunnel located at some depth underground. The results indicate that significant axial and circumferential strains may be generated on the body of an underground tunnel due to surface explosions located above the crown of the tunnel. The level of strain depends on the nature of the intervening soil medium and material of the tunnel.

Results of these experiments provide valuable understanding of the effects of surface blasts. These results will be useful in designing new embankments and underground structures as well as for developing protective retrofits for existing structures.