Anisotropic Consolidation Behavior of Ariake Clay from Three Different CRS Tests

Abstract

Three types of constant rate of strain (CRS) consolidation tests were conducted on samples of undisturbed Ariake clay, using a newly developed consolidometer, to investigate the anisotropic consolidation behavior of the clay. CRS tests conducted using vertically cut specimens (with respect to the in situ condition) tested with vertical (or end) drainage (with respect to test condition) were designated as CRS-V-V tests. Specimens cut vertically but with radial drainage were designated CRS-V-R, whereas those cut horizontally and tested with vertical drainage were designated CRS-H-V. The test results show that the ratio of the consolidation yield stress of a horizontally cut specimen (pch) to that of a vertically cut specimen (pcv) is in a range from 0.5 to 1.0. Both pcv and pch increased about 15 % with a tenfold increase in strain rate, but there was no clear difference in the degree of strain-rate dependency for pcv and pch. Values of the coefficient of consolidation obtained from CRS-H-V (chh) and CRS-V-R (chv) test are larger than those measured in CRS-V-V (cv) tests, and it has been identified that these differences arise mainly from the anisotropy of hydraulic conductivity (k). The ratio of k in the horizontal direction (kh) measured in a CRS-V-R test to that in the vertical direction (kv) from a CRS-V-V test is about 1.65, and the ratio of chv/cv is about 1.54. The value of kh from a CRS-H-V test is generally smaller than that from a CRS-V-R test.