Low Energy Dynamic Compaction (LEDC) is a recently adopted approach for the rapid improvement of the mechanical behaviour of soil to a relatively shallow depth over a limited area. This method of compaction is termed `low energy' because the energy input per blow is low compared with that imparted by traditional dynamic compaction techniques. The field apparatus for this method was designed originally by BSP/DRA for the rapid repair of bomb damaged airfield runways, but later adopted as a method of ground improvement. This thesis describes the design and operation of a unique model compactor simulating the action of a low energy compactor in the centrifuge. The centrifuge study has been undertaken at 20g using a tamper mass of 0.875 kg falling through 100mm onto a stiff aluminium target, having a mass 0.268 kg and a diameter of 100mm. This simulated a field scale tamper mass of approximately seven tonnes falling through two meters onto a target having a base area of 3.14m2. This research required the development, for use in the centrifuge, of a process monitoring system proposed by Allen (1996), where the improvement in the ground characteristics may be evaluated with the execution of the improvement process. The procedure was based on the principles of the WAK test ( Briaud and Lepert, 1990 ) which was devised to provide, by means of a very simple test, an estimate of the static stiffness of a soil/footing system, thus removing the necessity for expensive pre- and post- test investigations. The monitoring system required the innovative deployment of miniature instrumentation on the pounder and the target to measure both input force and output accelerations In order to analyse the soil response to the impact it is necessary to obtain both the signature of the energy input and soil response in terms of acceleration and transient earth pressures for each impact. This was achieved by the use of a dynamic load cell mounted on the drop weight, an accelerometer on the target and accelerometers and dynamic earth pressure cells embedded within the soil mass.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:495952 |
| Date | January 1999 |
| Creators | Parvizi, Mansour |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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