A set of saturated Ottawa sand models were treated with Microbially Induced Calcite Precipitation (MICP) and subjected to repeated shaking events using the 1-m radius centrifuge at the UC Davis Center for Geotechnical Modeling. Centrifuge models were constructed to initial relative densities (DR0) of approximately 38% and treated to light, moderate, and heavy levels of cementation (calcium carbonate contents by mass of approximately 0.8%, 1.4%, and 2.2%, respectively) as indicated by shear wave velocities (light ≈200 m/s, moderate ≈325 m/s, and heavy ≈600 m/s). The cemented centrifuge models are compared to a pair of uncemented saturated Ottawa sand models with initial DR0s of ≈38 and ≈53% and subjected to similar levels of shaking. Cone penetration resistances and shear wave velocities are monitored throughout shaking to investigate (1) the effect of cementation on cone penetration resistance, shear wave velocity, and cyclic resistance to liquefaction triggering and (2) the effect of shaking on cementation degradation. Accelerometers, pore pressure transducers, and a linear potentiometer are used to monitor the effect of cementation on liquefaction triggering and consequences. Cone penetration resistances and shear wave velocities are sensitive to light, moderate, and heavy levels of cementation (increases in penetration resistance from 2 to 5 MPa, 2 to 10 MPa, and 2 to 18 MPa and shear wave velocity from 140 to 200 m/s, 140 to 325 m/s, and 140 to 660 m/s, respectively), and are able to capture the effects of cementation degradation.

The effects of shaking history on CPT based liquefaction triggering correlations for clean saturated sand are examined using cone penetration resistance and cyclic strength data pairs from dynamic centrifuge model tests. Three model tests on a 9-m radius centrifuge examine liquefaction responses of level profiles of saturated Ottawa F-65 sand subjected to multiple (17 to 29) shaking events that produced successive changes in density and model response characteristics. Inverse analysis of data from dense accelerometer arrays are used to define time series of cyclic stress ratios and shear strains throughout the profile. Cyclic resistance ratios against triggering of ~100% excess pore pressure ratio in 15 equivalent uniform cycles are computed at multiple depths based on weighting of the cyclic stress ratio time series up to the time of triggering. Cone penetration tests performed at select times during each model test are used to define the variation in cone tip resistances with depth and shaking history. The resulting data pairs, with normalized cone tip resistances ranging from 20 to 340 and cyclic resistance ratios ranging from 0.1 to 2.0, show that both quantities progressively increase as a result of recurrent liquefaction events, and generally follow the trends predicted by case history based liquefaction triggering correlations. Three 1-m radius centrifuge tests of similar configurations produced consistent results. Implications for the interpretation of case histories and engineering practice are discussed.

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.

A set of saturated Ottawa sand models were treated with Microbially Induced Calcite Precipitation (MICP) and subjected to repeated shaking events using the 1-m radius centrifuge at the UC Davis Center for Geotechnical Modeling. Centrifuge models were constructed to initial relative densities (DR0) of approximately 38% and treated to light, moderate, and heavy levels of cementation (calcium carbonate contents by mass of approximately 0.8%, 1.4%, and 2.2%, respectively) as indicated by shear wave velocities (light ≈200 m/s, moderate ≈325 m/s, and heavy ≈600 m/s). The cemented centrifuge models are compared to a pair of uncemented saturated Ottawa sand models with initial DR0s of ≈38 and ≈53% and subjected to similar levels of shaking. Cone penetration resistances and shear wave velocities are monitored throughout shaking to investigate (1) the effect of cementation on cone penetration resistance, shear wave velocity, and cyclic resistance to liquefaction triggering and (2) the effect of shaking on cementation degradation. Accelerometers, pore pressure transducers, and a linear potentiometer are used to monitor the effect of cementation on liquefaction triggering and consequences. Cone penetration resistances and shear wave velocities are sensitive to light, moderate, and heavy levels of cementation (increases in penetration resistance from 2 to 5 MPa, 2 to 10 MPa, and 2 to 18 MPa and shear wave velocity from 140 to 200 m/s, 140 to 325 m/s, and 140 to 660 m/s, respectively), and are able to capture the effects of cementation degradation.

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.