INSTRUMENTAL PROJECTILES IN CENTRIFUGE MODELLING OF SEABED CONCENTRATION.
The paper discusses the design and construction of instrumented model projectiles and of the experimental installations for simulation of penetration to clay several km under the sea. The CESTA centrifuge was used at a length scale of 1/50 to reproduce a site of 40 m depth, 25 m diameter, using a minimum size instrumented model projectile of 1,3 cm diameter. The 10 m radius of the centrifuge minimized Coriolis effects as the projectile was shot by an airgun into the soft clay. The large clay sample could only be consolidated by the hydraulic gradient method, which took one to four months. The resulting cohesion was measured by a custom built apparatus for vane tests in centrifugation. Strain rate influences on strength were tested by shock triaxial tests in a specially built cell. Accelerations and forces on the projectile were measured and signals transmitted by unwinding thin wires. Stresses and accelerations were measured in the clay. Results from the projectile predicted quite well velocity and penetration depths measurements of projectiles dropped into the Atlantic Ocean during other European programs demonstrating the similarity. This main result was supported by the shock triaxial tests showing no appreciable viscous effects at strain rates up to 8 000 % S**-1. Vane tests showed the suitability of the consolidation method. Instrumented projectile tests using large centrifuges at low g levels can from now on be used in modelling the behaviour of the sea-bed for nuclear waste disposal feasibility studies, as has been done in contractual work with the Commission of the European Communities in the present case.
Bibliographic Reference: 2ND INTERNATIONAL CONFERENCE ON SOIL DYNAMICS AND ENGINEERING, ON BOARD OF THE LINER QUEEN ELIZABETH 2, JUNE 28-JULY 4, 1985 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 31863 ORA
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Record Number: 1989123067400 / Last updated on: 1987-01-01
Available languages: en