Effect of Partial Drainage on Cyclic Strengths of Saturated Sands in Dynamic Centrifuge Tests

Abstract

The effects of partial drainage on the cyclic strength of saturated sand in a set of dynamic centrifuge model tests were evaluated. Three models of level profiles of saturated Ottawa F-65 sand with initial relative densities of 25, 43, and 80% were tested using a 9-m radius centrifuge.Models were subjected to multiple sinusoidal shaking events with acceleration amplitudes ranging from 0.03 to 0.55g. The cyclic resistance ratios (CRR) obtained from inverse analyses of dense accelerometer and pore pressure transducer arrays were correlated with cone penetration resistances (qc1N) from in-flight cone penetration tests. Time histories of volumetric strain and surface settlement due to partial drainage were determined by inverse analyses of the array data and compared with measured surface settlements. The effect of volumetric strain on cyclic strength is examined through single element simulations using the constitutive model PM4Sand (version 3). Results of these simulations are compared to prior laboratory and numerical studies investigating the effect of partial saturation on cyclic strength. The magnitude of the volumetric strains developed in the centrifuge models due to partial drainage and their effects on the centrifuge CRR-qc1N correlation are examined.

Closure to “Simplified Procedure for Prediction of Earthquake-Induced Settlements in Partially Saturated Soils” by Abdülhakim Zeybek and Santana Phani Gopal Madabhushi

“…Partial drainage is explained by a rapid increase in the permeability of the sands at very low effective stresses typically below 0.1 kPa (Haigh et al 2012). The degree of partial drainage may increase with a more pervious boundary, increased hydraulic conductivity, and decreased compressibility (Darby et al 2019). Based on an extensive centrifuge study, Zeybek and Madabhushi (2017c) identified the prevailing deformation mechanisms at play in saturated and partially saturated sands.…”