Abstract
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 eTas the number of load cycles increases. The terminal void ratio eTis a function of the initial void ratio e0and 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→103for 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 K0during 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.
Highlights
Geotechnical structures often experience repetitive loading cycles
This paper extends a previous study by the authors (Chong & Santamarina, 2016) to address a large number of load cycles (i.e. N = 104), various stress amplitude ratios Δσ/σ0 and the analysis of elastic cyclic deformation and the accumulation of plastic strain
The ratio M/Gmax is explored, between the constrained modulus M preferred for 1D deformation analysis and the maximum shear stiffness Gmax obtained from shear wave velocity
Summary
Geotechnical structures often experience repetitive loading cycles. Previous studies have explored the soil response to all kinds of repetitive loads, including: mechanical cycles associated with wind, waves, pavements, railroads and foundations (Monismith et al, 1975; Poulos, 1989; Jardine, 1991; Brown, 1996; White & Lehane, 2004; Wichtmann et al, 2005, 2010a; Andersen, 2009; LeBlanc et al, 2010; Indraratna et al, 2013; Wu et al, 2017; Guo et al, 2018); chemical cyclic changes in pore fluid (Di Maio, 1996; Musso et al, 2003); thermal cycles (Viklander, 1998; Pasten & Santamarina, 2014; Di Donna & Laloui, 2015); drying and wetting sequences (Albrecht & Benson, 2001; Alonso et al, 2005; Tripathy & Rao, 2009); freeze–thaw cycles (Chamberlain et al, 1990; Viklander, 1998; Qi et al, 2008); and repetitive changes in pore water pressure (Orense et al, 2004; Nakata et al, 2013; Huang, 2016).The design of geo-structures needs to consider the influence of repetitive loads on long-term performance, serviceability and safety. This paper extends a previous study by the authors (Chong & Santamarina, 2016) to address a large number of load cycles (i.e. N = 104), various stress amplitude ratios Δσ/σ0 and the analysis of elastic cyclic deformation and the accumulation of plastic strain.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
