Abstract
This thesis examines the influence of the stress paths and consolidation history on the results of dynamic penetration tests and on the deformation behaviour of a sand, and the implications of the results on settlement predictions in granular material. For this purpose, specimens of saturated Leighton Buzzard sand were prepared in the laboratory inside a triaxial chamber 435 mm in diameter x 660 mm high, by sedimentation in water. After prestressing through different stress paths, dynamic penetration tests were performed on the specimens, penetration from each blow was recorded, and pore water pressure developed under the tip and at two different levels along the side of the penetrometer with elapsed time was measured by connecting the transducers inside the penetrometer to a system which enable a desk-top computer to store the results on cartridges with two channels. The results can be processed at any time using the same computer. Attempts to measure the acceleration and the velocity of the penetrometers were made by fixing an accelerometer inside the penetrometer and connecting it to the same system to be recorded and processed. High speed photography was used to find the elapsed time required for the penetrometer under each blow. The scale effect on the penetration resistance was examined by running tests using different sized penetrometers. In the second phase of testing a large number of stress path tests were carried out on the same sand having the same density under computer control in Bishop Wesley cell, following the stress paths used in the large triaxial chamber. At the end of each stress path a standard increment of sigmav' = 100 kN/m2, sigmah' = 30 kN/m2 was applied to simulate the stress increase on an element of soil beneath a foundation. Vertical strains under this standard increment were used to calculate a tangent deformation modulus (Mt) where Mt = Different available laboratory methods were tried to find the value of the coefficient of earth pressure at rest (KO) for the same sand at same density. A computer programme was prepared to find KO under computer control in the Bishop-Wesley cell, and a new technique for finding Ko was developed with a new transducer using the (Hall effect) phonomenon which enabled the operater to control the lateral pressure by means of a desk-top computer. The results showed-that the stress level has a great effect on the penetration resistance and a small effect on the compressibility of the sand, while the prestressing of the sand has a large effect on the compressibility and very small effect on the penetration, resistance.