UNDRAINED CYCLIC SHEAR BEHAVIOR OF CLAY UNDER DRASTICALLY CHANGED LOADING RATE

Authors

  • Imran Khan
  • Kentaro Nakai
  • Toshihiro Noda

Keywords:

Clay, Cyclic loading, Loading rate, Excess pore water pressure

Abstract


The earthquake damage prediction is mainly focused on the seismic instability of sandy
foundations although the clayey foundation could also be vulnerable to earthquake damage. Moreover, it is
known that clayey soil shows a marked loading rate dependency in monotonic shear behavior due to its low
permeability. Therefore, this paper aims to determine the undrained cyclic shear behavior of clayey soil
under a drastically changed loading rate. Reconstituted clayey samples were subjected to undrained cyclic
triaxial compression/extension tests with loading rate from 1.0Hz to 0.0042Hz by stress control, and
0.01%/min by strain control. The cyclic loading was stopped when the double amplitude exceeded 5%. Then,
the specimen was left for a while in an undrained condition, until the value of pore water pressure converged.
Results revealed that as the loading rate decreases, the number of cycles that corresponds to DA=2% and 5%
also decreased. Therefore, the degree of strain evolution varies depending on the loading rate and the
undrained shear strength also varies depending on the cyclic loading rate. This is because when the cyclic
loading rate was high; the pore water did not migrate sufficiently, leading to the non-uniform distribution of
the excess pore water pressure inside the specimen. However, the final values of excess pore water pressure
after the homogenization process was the same regardless of the loading rate. This means that if sufficient
time is left after cyclic loading, the final mean effective stress value becomes equal regardless of the loading
rate

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Published

2020-02-26

How to Cite

Imran Khan, Kentaro Nakai, & Toshihiro Noda. (2020). UNDRAINED CYCLIC SHEAR BEHAVIOR OF CLAY UNDER DRASTICALLY CHANGED LOADING RATE. GEOMATE Journal, 18(66), 16–23. Retrieved from https://geomatejournal.com/geomate/article/view/430