Civil Engineering ETDs

Publication Date

3-19-1974

Abstract

The densification behavior of 13 different types of materials was investigated by subjecting each material to vertical simple harmonic motion using an electromagnetic vibrator. A total of more than 1000 maximum density tests were performed. The soil parameters investigated were angularity, uniformity coefficient, percentage of fines and specific gravity. The vibration parameters investigated were frequency, acceleration, displacement and time of vibration. To study the effect of angularity, four different types of materials ranging from angular to rounded were tested. The effect of uniformity coeffi­cient, percentage of fines and specific gravity was investigated by varying the uniformity coefficient from 2 to 20, the percentage of fines from 1 to 30 and the specific gravity from 2.62 to 4.0. The ef­fect of initial saturation on densification was investigated by per­forming tests in dry, initially saturated undrained and initially saturated drained conditions. The frequency of vibration was varied between 20 and 60 cps, the acceleration was varied between 0.5 and 3,5g, the velocity was varied between 0.51 and 9.21 inch/sec and the dis­placement was varied between 0.00135 and 0.0733 inch. Preliminary tests were performed with durations of vibration ranging from 30 seconds to 5 minutes.

It was found that at the same value of uniformity coefficient, minimum and maximum densities decreased with increasing angularity. At the same value of angularity, minimum and maximum densities increased with increasing uniformity coefficient. Sends containing up to thirty percent fines could be successfully densified by vibrations. The minimum and maximum densities increased with increasing percentage of fines and increasing specific gravity. Highest densities for cohesionless soils were obtained by vibrating them in a fully saturated state. In general, the optimum frequency, acceleration, velocity and displacement were found to be different for every material. However, acceleration appeared to be the most important vibration parameter. A duration of vibration of two minutes was found to be adequate for producing complete densi­fication of cohesionless materials containing up to thirty percent fines.

On the basis of the present and other recent investigations, several modifications are suggested to the ASTM standard method for relative density determination of cohesionless soils. It is suggested that the vibrating table specified by the ASTM standard method be eliminated and the soil container-be rigidly attached to the moving core of an electromagnetic vibrator producing simple harmonic motion in vertical or horizontal direction. It is suggested that the tests for maximum density determination be performed under no surcharge and at various values of frequencies and accelerations. It is suggested that the dur­ation of vibration be reduced to about two minutes. It was found that the minimum densities obtained by using the ASTM standard method were much higher than those obtained by several other methods studied in this investigation. It is therefore suggested that the ASTM standard method for minimum density determination of cohesionless soils be care­fully examined and be replaced by the method used to obtain minimum den­sities in this investigation.

Document Type

Dissertation

Language

English

Degree Name

Civil Engineering

Level of Degree

Doctoral

Department Name

Civil Engineering

First Committee Member (Chair)

George Emmanuel Triandafilidis

Second Committee Member

Richard Hudson Clough

Third Committee Member

John Bryan Carney

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