Rate-dependency and Stress-Relaxation of Unsaturated Clays

Meghdad Bagheri, Mohammad Rezania, Mohaddeseh Mousavi Nezhad

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Abstract

This paper presents the experimental program conducted for evaluation of the rate-dependent and stress-relaxation behavior of unsaturated reconstituted London clay. A series of drained constant rate of strain (CRS) compression-relaxation tests with single-staged (SS-CRS) and multistaged (MS-CRS) loading modes was performed in an innovative CRS oedometer cell where soil suction evolutions were monitored using two high-capacity tensiometers (HCTs). Specimens were tested at two strain rates of 4.8×10−7 and 2.4×10−6  s−1 and over a suction range of 0–1,905 kPa. The coupled and independent effects of strain rate and soil suction on one-dimensional stress–strain and stress-relaxation responses, including the effects of prerelaxation strain, stress, and strain rate under both saturated and unsaturated conditions, were evaluated. An increase in suction and strain rate resulted in an increase of the yield vertical net stress (σp). Furthermore, it was observed that the rate and magnitude of the relaxed stresses increased with increases in prerelaxation strain, stress, and strain rate, and decreased with an increase in soil suction. At constant suction, an increase in the prerelaxation strain rate by a factor of five resulted in an increase of the relaxed stresses by a factor of 2.2–3.6. Moreover, the coefficient of relaxation (Rα) was found to be suction dependent, falling within a range of 0.011–0.019 and 0.017–0.029, respectively, for slow and fast strain rates during MS-CRS tests. Comparing these results with the Cα/Cc ratio obtained from conventional multistage loading (MSL) oedometer test results revealed the validity of Rα=Cα/Cc correlation for unsaturated reconstituted specimens.
Original languageEnglish
Article number04019128
JournalInternational Journal of Geomechanics
Volume19
Issue number12
Early online date11 Oct 2019
DOIs
Publication statusPublished - 1 Dec 2019

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stress relaxation
strain rate
suction
clay
London Clay
oedometer test
tensiometer
soil
rate
compression
unsaturated conditions
program evaluation
saturated conditions
tensiometers
testing

Bibliographical note

Copyright © and Moral Rights are retained by the author(s) and/ or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders.

Keywords

  • Strain rate
  • Stress relaxation
  • Suction
  • Unsaturated soils

ASJC Scopus subject areas

  • Soil Science

Cite this

Rate-dependency and Stress-Relaxation of Unsaturated Clays. / Bagheri, Meghdad; Rezania, Mohammad; Mousavi Nezhad, Mohaddeseh.

In: International Journal of Geomechanics, Vol. 19, No. 12, 04019128, 01.12.2019.

Research output: Contribution to journalArticle

Bagheri, Meghdad ; Rezania, Mohammad ; Mousavi Nezhad, Mohaddeseh. / Rate-dependency and Stress-Relaxation of Unsaturated Clays. In: International Journal of Geomechanics. 2019 ; Vol. 19, No. 12.
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