Typescript. / Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

Includes bibliography. / The thesis consists of a literature review and a limited experimental investigation in a soils laboratory. The objective of the literature review is to determine what standard laboratory test methods based on vibration exist for the control of compaction, to what soil types these tests are applicable and what the factors are which affect laboratory vibratory compaction. The study revealed that extensive research has been carried out in the USA and Europe, where standard laboratory compaction tests exist for the determination of the maximum dry density of cohesionless, free-draining soil. The US methods are based on the use of a vibratory table, while the European practice is based on the use of a vibratory tamper. No standard tests appear to exist for soil exhibiting cohesion, though limited research has been carried out in the USA into the behaviour of such soils under laboratory vibratory compaction. The factors; frequency, amplitude, mould size and shape surcharge intensity and manner of application, soil type, time of vibration, number of layers and moisture content are all reported to have an effect on the maximum dry density achievable. It has been recognised that significant interaction occurs between the factors affecting vibratory compaction, but the extent of the interaction appears to be only partly understood. The objective of the limited experimental program was to determine whether a specific graded crushed stone could be compacted to Modified AASHTO maximum dry density with a laboratory vibratory compaction technique using a vibratory table, and how this could best be achieved. The effects on dry density of changing the frequency, the time of vibration, mould size, surcharge pressure, grading and moisture content were investigated. It is concluded that the graded crushed stone in question can be compacted to Mod. AASHTO maximum dry density but that before reliable reproducible results can be achieved with this type of test further work is necessary. Such research should be aimed at investigating the interaction effect between the amplitude of vibration, the soil type and the type and intensity of the applied surcharge pressure.

In developing a constitutive model that could predict the settlement due to the collapse, several goals needed to be met. These were to gain an understanding of the collapse phenomenon, knowing the soil properties at the natural water content and how they change after collapse, and develop and test the new model. It was felt that laboratory testing could be of use. The types of test conducted included use of the Oedometer, Pressuremeter, and Triaxial tests. The material that was used for the testing was a "generic" soil manufactured out of diatomite. In all of the tests the soil was tested dry and saturated in order to establish state limits of the soil. Next, the soil was loaded dry then inundated which initiated the collapse of the soil. The stress and strains were continually recorded. From the testing it was concluded that there is a stress-strain region where after collapse the soil looses considerable strength. With increasing stress and strain the soil eventually becomes stronger. From the triaxial tests, the stress-strain data from this "region of collapse" was used in a constitutive model. Stress paths from the Oedometer and Pressuremeter tests were then successfully applied to the model. The constitutive model used was an elasto plastic model. The elastic and plastic strain components were provided using functions for yielding, hardening, plastic potential, and failure as proposed by Paul Lade in his work on cohesionless, frictional materials. Results from the conventional triaxial shear tests and isotropic compression tests were used to derive the values of the functions for the model. The end result was three dimensional surfaces for failure, yielding, plastic work and plastic potential for the dry and saturated soil in the zone of collapse.