Figure 12. Self-weight consolidation test device

This test is useful for determining the upper portion of the void ratio-effective

stress and void ratio-permeability relationships; it is presently the only method

available to determine this needed information.

The self-weight testing device is shown in Figure I2. This device consists of

an outer plexiglass cylinder that encircles a second plexiglass column composed

of either 0.25- or 0.50-in.-thick rings. The device allows consolidation testing

and subsequent incremental sampling of a specimen 6 in. in diameter and up to

12 in. high. The material tested in this device should consist of only the fine-

grained portion of the sediment, i.e., that portion passing the No. 40 sieve. Use

of only minus No. 40 material is necessary to prevent, or minimize, segregation

of the coarser fraction from the high void ratio slurry being tested.

The sediment is mixed with water from the dredging site to form a slurry. In

order to develop the entire e-)1 relationship, this slurry should always be at a

void ratio greater than the void ratio at zero effective stress, eoo, which is the void

ratio of the dredged material after sedimentation and before consolidation. The

initial void ratios usually used in this test range from approximately 10.0 to 16.0.

The slurry is placed in the consolidometer, and it is allowed to undergo self-

weight consolidation. Deformation versus time data are collected during the

consolidation process. After the completion of primary consolidation, the test

device is disassembled and the specimen is sampled at 0.25- or 0.50-in. intervals

throughout its depth to obtain the necessary data to calculate void ratio, effective

stress, and permeability values for the upper portion of the e-)1 and e-k curves.

Figure I2.

Self-weight consolidation test device

Appendix I Consolidation Testing