Study on the effects of liquefaction soil layer thickness and depth on site surface acceleration response spectra pre- and post-liquefaction

Dongsong Song , Hongshuai Liu

Abstract

Soil liquefaction is a key factor leading to building instability and foundation failure during earthquakes. To reveal the influence mechanism of the liquefiable soil layer on surface acceleration response spectra during the "pre-liquefaction" and "post-liquefaction" stages, this study established a 30 m total thickness liquefaction site soil column model using OpenSees. The "surface response spectrum intensity ratio" served as the core indicator to quantitatively analyze the effects of soil layer parameters and ground motions. The results indicate that: (1) Spectra differences between sites are minimal per-liquefaction but become significant post-liquefaction, showing a clear isolation effect. (2) Post-liquefaction site, regardless of the soil layer distribution, the spectra intensity ratios for both short-period (0.01-0.3 s) and long-period (0.8-10 s) ranges are less than 1, reflecting an isolation effect. (3) The spectra intensity ratio increases with the relative density of the liquefiable soil layer and decreases as a power function with increasing thickness and depth. When the thickness ratio (liquefiable soil layer thickness/total soil layer thickness) and depth ratio (liquefiable soil layer depth/total soil layer thickness) are less than 0.1, the growth rate of the isolation effect is the fastest; when the ratios exceed 0.4, the isolation effect stabilizes and reaches its maximum. (4) As the peak ground acceleration (PGA) of the input ground motion increases, the spectra intensity ratio gradually decreases under non-pulse ground motions, while it first decreases and then increases under pulse ground motions. The findings of this study can provide some reference for the seismic design of liquefiable sites.

Key Words

liquefaction soil layers; nonlinear numerical analysis; post-liquefaction surface response spectra; surface response spectra intensity ratios

Address

Dongsong Song — 1) Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China; 2) Key Laboratory of Earthquake Disaster Mitigation, Ministry of Emergency Management, Harbin, China; 3) State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structure, Shijiazhuang Tiedao University, Shijiazhuang, China
Hongshuai Liu — 1) Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China; 2) Key Laboratory of Earthquake Disaster Mitigation, Ministry of Emergency Management, Harbin, China; 3) College of Civil Engineering and Architecture, Hebei University, Baoding, China

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