In-Flight Density Profiling System

Mechanical Design

of an

In-flight Density Profiling System

"SUMMARY"

Prepared for

Andy Fisher

Faculty of Engineering & Applied Science

Memorial University of Newfoundland

Prepared by:

CCCC Engineering

Jordan Cooper (9134339)

Jason Cole (8147720)

Elvis Chippett (9152067)

Richard Croucher (9165713)

Design of an In-flight Density Profiling System

Design of an In-flight Density Profiling System

Supervisor: Dr. Ian McDermott, C-CORE, St. John's

Team Members: Jason Cole (Team Leader), Jordan Cooper, Elvis Chippett, Richard Croucher

Design of an In-flight Density Profiling System

C-CORE's geotechnical centrifuge is used for testing physical models of soil/structure interactions at stresses equivalent to those found in situ, this centrifuge relies on the rotation of the sample to impart stress upon the sample. The rotating arm of the geotechnical centrifuge is 5.5 meters in radius and can impart accelerations of 200 gravities on the models. At present, density measurements can only be made on the centrifuge soil samples when the apparatus is stationary.

A need exists for the current stationary point measurement system to be upgraded to a system capable of vertically scanning the soil model to provide a density profile. The objective of this project is to provide C-CORE with such a system. The density profiler would be required to withstand accelerations of up to 120 gravities.

The system will be designed to meet the following criteria:

- the gamma source and detector must:

- be capable of synchronized vertical movement of 1 meter

- not rotate in the horizontal plane to ensure accurate alignment and readings

- the proposed design must:

- withstand accelerations of up to 120 gravities

- interface smoothly with existing instrumentation on the test column

- the components inside the test column must withstand the highest pressures generated at 120 gravities ( approximately 2.4 MPa)

- the gamma source must be placed in the test column last to minimize exposure time

- the linear actuator cannot be a dedicated component of the proposed design

To assist in this design problem, the project team would draw upon existing motorized profiling systems which are in frequent use in C-CORE centrifuge experimentation. The proposed system will incorporate a radioactive gamma source, a geiger tube detector a modified one meter test column, an existing linear actuator, and a cable/pulley system to facilitate synchronized vertical movement of the source and detector. The one meter test column will be filled with a sediment slurry and flown in C-CORE's geotechnical centrifuge. During flight, the gamma source and detector will vertically scan the test column sending and receiving gamma rays through the soil sample. As the centrifugal forces acts upon the slurry, the soil will settle to the bottom causing changes in density. The density profiles made during flight will give valuable information regarding the settling of soils over time. This is the basis of the sensing principle that will be utilized by the mechanical prototype that our group will design.

This system will be prototyped and tested in February of 1998.