EGEL
Energy GeoEngineering Laboratory

Park, J. and Santamarina, J.C, 2018

Sand response to a large number of loading cycles under zero-lateral-strain conditions: evolution of void ratio and small-strain stiffness

Park, J. & Santamarina, J.C, 2018  Sand response to a large number of loading cycles under zero-lateral-strain conditions: evolution of void ratio and small-strain stiffness , Géotechnique [https://doi.org/10.1680/jgeot.17.P.124]
Park, J. & Santamarina, J.C, 2018
compressibility; creep; deformation; settlement; stiffness; vibration
2018
​Geotechnical structures often experience a large number of repetitive loading cycles. This research
examines the quasi-static mechanical response of sands subjected to repetitive loads under
zero-lateral-strain boundary conditions. The experimental study uses an automatic repetitive loading
frame operated with pneumatic pistons. Both vertical deformation and shear wave velocity are
continuously monitored during 10 000 repetitive loading cycles. The void ratio evolves towards the
terminal void ratio eT as the number of load cycles increases. The terminal void ratio eT is a function of
the initial void ratio e0 and the stress amplitude ratio Δσ/σ0. The number of cycles N* required to reach
half of the final volume contraction ranges from N*!1 for densely packed sands (e0!emin) to N!103
for loosely packed sands (e0!emax). As the soil approaches terminal density at a large number of cycles,
peak-to-peak strains are dominated by elastic deformations, and the minute plastic strains that remain
in every cycle reflect local and sequential contact events. The shear wave velocity increases during cyclic
loading with data suggesting a gradual increase in the coefficient of earth pressure K0 during repetitive
loading. Changes in shear wave velocity track the evolution of the constrained modulus M; in fact, the
constrained modulus can be estimated from the shear wave velocity to compute soil deformation in a
given cycle. A simple procedure is suggested to estimate the potential settlement a layer may experience
when subjected to repetitive mechanical loads.​