Journal Published Online: 16 April 2020
Volume 44, Issue 4

Design and Development of an In-Flight Actuator for Modeling Dynamic Compaction in a Geotechnical Centrifuge



The objective of this article is to present the design details and performance of an in-flight actuator for simulating dynamic compaction (DC) at enhanced gravities in a geotechnical centrifuge. The developed actuator is equipped with an automatized lifting and dropping mechanism to induce repeated impacts on the soil surface at high gravities, with prototype energies varying from 50 to 400 t-m. In addition, the developed actuator encompasses a wide range of tamper shapes, tamper diameter, and mass coupled with variable drop heights during centrifuge testing, thereby simulating both low-energy impacts and high-energy DC processes adopted in the field. The various components and working mechanism of the developed actuator are discussed, with particular emphasis on measures taken for ensuring vertical alignment of tamper and for minimizing Coriolis acceleration generated during flight. In this article, the results of four calibration tests and four centrifuge model tests of DC on a typical loose granular deposit are discussed, conducted in a 4.5-m radius large beam centrifuge facility available at IIT Bombay, India. The calibration results indicate that the impact frequency can be regulated remotely by controlling the motor voltage to enable monitoring of pore water pressure build-up in saturated soils during impact and its subsequent dissipation. The average time interval between successive impacts, in this case, is observed to be uniform and approximately 1.4–2.3 min in prototype dimensions. Further, the analysis of data captured by pore water pressure transducers and accelerometers, coupled with GeoPIV-based image analysis, was employed to demonstrate the effectiveness of DC in granular soils using the developed actuator for various tamper energies and saturation levels. The results are interpreted in terms of pore water pressure variations during impacts, crater formations, surface settlements, induced ground velocities and peak accelerations, and increases in relative density of the soil after DC.

Author Information

Kundu, Saptarshi
Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India
Viswanadham, B. V. S.
Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India
Pages: 28
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Stock #: GTJ20190169
ISSN: 0149-6115
DOI: 10.1520/GTJ20190169