The effect of shaking history on cone penetration resistance, cyclic resistance ratio, and their correlation to each other for saturated sand is examined using centrifuge model tests. Prior laboratory and centrifuge modeling studies have shown strain history can have a strong effect on the cyclic strength of sand, but data describing how these effects track with cone penetration resistance are lacking. The effects of shaking history on cone penetration resistance and cyclic strength are investigated using centrifuge models of saturated Ottawa sand on a 1-m radius centrifuge with a 6-mm diameter cone penetrometer. The centrifuge models are subjected to a series of shaking events at progressively increasing amplitudes until liquefaction is triggered. This motion is repeated until the sand no longer liquefies. Cone penetration tests are performed before any shaking, after liquefaction is triggered, and after liquefaction no longer occurs. Inverse analyses of accelerometer array data are used to compute profiles of dynamic shear stresses and strains. The results are used to examine the effects of prior strain history on cone penetration resistance, cyclic resistance ratio, and their correlation to each other. The centrifuge test results are also compared with a case history-based liquefaction triggering correlation.
Mechanistic approaches for developing cone penetration test-based liquefaction triggering correlations are presented and evaluated with an application to Ottawa sand. The mechanistic approaches utilize combinations of data from: undrained cyclic direct simple shear tests, dynamic geotechnical centrifuge tests with in-flight cone penetration profiles, and cone penetration simulations. Cyclic direct simple shear tests on Ottawa sand characterize the relationship between cyclic resistance ratio ( ) and relative density ( ). Relationships between cone tip resistance ( ) and are developed from geotechnical centrifuge tests and cone penetration simulations. Penetration simulations using the MIT-S1 constitutive model with three different calibrations for Ottawa sand examine the role of critical state line shape and position on simulated values. The − relationship from laboratory tests is composed with measured and simulated − relationships via common values to develop − relationships. An alternative − relationship is developed from inverse analyses of centrifuge test sensor array data (i.e., arrays of accelerometers and pore pressure sensors). The results of these different approaches are compared to case history-based correlations for clean sand and their relative merits discussed.Recommendations are provided for future application of these mechanistic approaches for developing liquefaction triggering correlations of poorly characterized or unique soils.
The effect of prior strain history on cyclic strength and cone penetration test (CPT) tip resistance of nonplastic silica silt is evaluated. Undrained cyclic direct simple shear (DSS) tests with multiple cyclic shearing and reconsolidation stages are performed to characterize the evolution of cyclic strength with strain history. Cyclic strengths are evaluated for maximum shear strains of 1% and 3% in 15 cycles. Drained CPT tip resistances are estimated from simulated cavity expansion limit pressures. Cavity expansion simulations allowing for changes in density from multiple cyclic loading and reconsolidation stages are performed in the finite difference program FLAC (Itasca 2014) using a modified version of the MIT-S1 elasto-plastic constitutive model (Pestana et al. 2002, Jaeger et al. 2012). Calibrations of MIT-S1 are performed using drained and undrained monotonic DSS tests as well as high stress one-dimensional compression testing. Leblanc and Randolph's method (2008) for projecting cavity expansion limit pressures onto a cone face is used to estimate CPT tip resistances. The progression of cyclic strength and simulated CPT tip resistance during a series of cyclic loading and reconsolidation stages is presented. The developed relationships between cyclic strength and CPT tip resistance are shown to track the curvature of corresponding semi-empirical qc1Ncs-CRR triggering curves. Dependence of the presented relationships on failure criterion (maximum shear strain) is shown to be qualitatively consistent with the literature.
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