Date of Award


Degree Type


Degree Name

Master of Science in Ocean Engineering


Ocean Engineering

First Advisor

Armand J. Silva


The objective of this investigation.was to study the strength and stress-strain properties of "undisturbed" and reconstituted-reconsolidated (remolded) samples of two Pacific (MPG-1) deep-sea sediments; illite and smectite. Isotropically consolidated undrained (CIU) triaxial tests were conducted on eleven series of samples, from which the basic soil parameters of effective cohesion () and effective angle of friction (ø) were determined.

An undisturbed smectite series (LL-44 GPC-3 1800 cm) had a friction angle of 35.5° and two undisturbed illite series (MA-02 GC-04 100 and 200 cm) had friction angles of 33. 0° and 34.8°. Friction angles for the smectite sediments were apparently not significantly affected by the type of remolding-reconsolidation process used in the test program, while illite samples exhibited a 30% reduction in friction angle due to remolding. Compared under the same conditions, undisturbed samples had greater drained and undrained strengths than the remolded samples, and smectite samples had greater drained and undrained strengths than the illite samples.

Using a hyperbolic stress-strain theory, the tangent Young's moduli and hyperbolic deviator stresses were determined for the samples . With the exclusion of samples which exhibited strain softening behavior, there was an excellent correlation between the experimental and hyperbolic values.

A new lateral strain gauge was built to measure lateral deformations of the samples during uniaxial compression. From these measurements, values of Poisson's ratio were calculated assuming a parabolic deformational shape. For a majority of samples, the standard area correction underestimated the true area of the samples.