The results of consolidated-undrained (R) triaxial compression tests with pore pressure measurements performed to determine the effects of strain rate on the strength and deformation characteristics of Vicksburg buckshot clay (CH) are presented and analyzed in this report. The 1.4-in.-dia triaxial specimens were compacted with a Harvard miniature compactor to 95 percent of maximum dry density derived from the standard effort compaction test with water contents 2 percentage points wet of standard optimum. Standard caps and bases (having the same diameter as the test specimen, with 1-in.-diam rigid porous inserts and drainage connections) were used in the triaxial tests. After back-pressure saturation and consolidation under effective confining pressures of 0.5 and 5.0 kg per sq cm, specimens with an without filter strips were axially loaded at rates of strain varying from 1.2 to 0.0012 percent per minute. Data presented include stress-strain curves, pore pressure observations, final water content distributions within the specimens, and shear strength envelopes based on total stresses. (Author).

The results of a series of consolidated-undrained (CU) triaxial compression tests performed on normally consolidated and overconsolidated specimes of two clays consolidated both isotropically (ICU tests) and anisotropically (ACU tests) are presented and analyzed in this report. The specimens were trimmed from samples of Vicksburg Buckshot clay (LL = 57) and a clay from the East Atchafalaya Basin Protection Levee (EABPL) project area (LL = 79), both of which had been consolidated from a slurry in large-diameter consolidometers under a maximum vertical consolidation pressure of 3.0 kg/sq cm. Data presented include stress-strain curves, pore pressure observations, final water content distributions within the specimens, and shear strength envelopes based on total and effective stresses. Test results indicate that the change in volume during consolidation and the water content at the end of consolidation are not a unique function of the vertical consolidation stresses but are related to the mean effective consolidation stress. Total stress envelopes based on Taylor's method of deriving strengths of anisotropically consolidated specimens from test results obtained from isotropically consolidated specimens slightly underestimate observed values. In this context, Taylor's method is an appropriate means of predicting strengths for various K sub c ratios from conventional ICU tests. Use of hyperbolic stress-strain relationships derived from ICU tests in finite element codes for ACU conditions will lead to erroneous results. Further testing of anisotropically consolidated soils under stress systems that better simulate in situ conditions is needed.

The paper first covers common problems with testing equipment and procedures that cause errors in the measured properties of the soil specimen, with emphasis on consolidated-undrained (CU) and consolidated-drained (CD) triaxial tests. These problems are divided into three categories: errors that can be handled via appropriate corrections; errors that must be avoided; and potential errors that must be evaluated when selecting test procedures or interpreting measured data, the most important being the nonuniform stresses and strains caused by frictional end caps. The paper then assesses the use of triaxial testing in practice to predict undrained stability and deformations for saturated cohesive deposits. Based on considerations of strain rate effects, soil anisotropy, disturbance from tube sampling, and results from case histories of failures, the authors make four recommendations. 1. UU compression tests should not be used as the principal means of estimating in situ undrained strengths because the values can be either significantly too high or too low. 2. CIU compression tests have little value because the measured undrained strength will be unsafe for stability analyses, and the stress-strain data do not simulate in situ behavior. 3. Therefore, more reliance should be placed on CKoU compression and extension tests, which would be aided by the availability of more reliable and less expensive automated "stress path" triaxial cells. 4. Oedometer tests should always be conducted to ascertain the stress history of the deposit.

This volume contains seven keynote lectures and over 100 technical contributions by scientists, researchers, engineers and students from more than 25 countries and regions worldwide on the subject of soft soil engineering.