الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This research presented a new concept to conduct a quality control on backfill by ’nag the free vibrating frequency of the soil and calibrate it with the dry unit weight three methods, laboratory tests, numerical model and field work. from the results of all the three methods, the following can be concluded: •There is a linear correlation between the dry unit weight of the soil and its free vibrating frequency regardless of the type of the soi I.
•In similar soil type and accelerometer mounting system, the linear relation coefficient is almost identical.
•Accelerometer mounting system effect on the correlation results is insignificant on measuring the free vibrating frequency of the soil.
•Free vibrating frequency of the soil represents the overall stiffness of the soil rather than the dry unit weight. This fact is confirmed from the visual observations during the field tests.
•Modulus of elasticity of soil is more significant in measuring the free vibrating frequency of the soil. Modulus of elasticity of soil is strongly correlated to the dry unit weight of soil, and in many cases, more important to evaluate than the dry unit weight but until now, it is difficult to measure accurately and swiftly in the field.
•The effect of the method of generating the exciting waves though the soil and its energy on the free vibrating frequency is insignificant. The current research show that when varying the energy of the shock in the different tests conducted throughout the research program, the free vibrating frequency of the soil is almost unchanged as long as other conditions are kept similar.
•The in-situ dry unit weight can be determined by means of calibrating the recorded in-situ free vibrating frequency against values of in-situ dry unit weight determined by other means such as sand cone or balloon tests.