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1. In-Situ Liquefaction Testing of a Medium Dense Sand Deposit and Comparison to Case History- and Laboratory-Based Cyclic Stress and Strain Evaluations

   https://doi.org/10.1007/978-3-031-11898-2_32  

   Stuedlein, A.W.; Jana, A. (September 2022, 4th International Conference on Performance Based Design in Earthquake Geotechnical Engineering)

   Wang, L.; Zhang, J.-M.; Wang, R. (Ed.)

   Observations of the dynamic loading and liquefaction response of a deep medium dense sand deposit to controlled blasting have allowed quantification of its large-volume dynamic behavior from the linear-elastic to nonlinear-inelastic regimes under in-situ conditions unaffected by the influence of sample disturbance or imposed laboratory boundary conditions. The dynamic response of the sand was shown to be governed by the S-waves resulting from blast-induced ground motions, the frequencies of which lie within the range of earthquake ground motions. The experimentally derived dataset allowed ready interpretation of the in-situ γ-ue responses under the cyclic strain approach. However, practitioners have more commonly interpreted cyclic behavior using the cyclic stress-based approach; thus this paper also presents the methodology implemented to interpret the equivalent number of stress cycles, Neq, and deduce the cyclic stress ratios, CSRs, generated during blast-induced shearing to provide a comprehensive comparison of the cyclic resistance of the in-situ and constant-volume, stress- and strain-controlled cyclic direct simple shear (DSS) behavior of reconstituted sand specimens consolidated to the in-situ vertical effective stress, relative density, and Vs. The multi-directional cyclic resistance of the in-situ deposit was observed to be larger than that derived from the results of the cyclic strain and stress interpretations of the uniaxial DSS test data, indicating the substantial contributions of natural soil fabric and partial drainage to liquefaction resistance during shaking. The cyclic resistance ratios, CRRs, computed using case history-based liquefaction triggering procedures based on the SPT, CPT, and Vs are compared to that determined from in-situ CRR-Neq relationships considering justified, assumed slopes of the CRR-N curve, indicating variable degrees of accuracy relative to the in-situ CRR, all of which were smaller than that associated with the in-situ cyclic resistance. 

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2. Quality Assurance Criteria for Cyclic Direct Simple Shear Tests for Evaluating Liquefaction Triggering Characteristics of Cohesionless Soils

   https://doi.org/10.32075/17ECSMGE-2019-0470  

   Ulmer, K.J. (September 2019, Proceedings of the XVII ECSMGE-2019)

   Undrained or constant volume direct simple shear (CDSS) tests are commonly used to evaluate the liquefaction triggering characteristics of cohesionless soils. However, while the American Society for Testing of Materials (ASTM) has developed standards for monotonic direct simple shear testing, they have not developed a standard for CDSS. As a result, herein the authors review their test database and assign “grades” A-D to different aspects of the tests, e.g.: accumulated shear strain and imposed shear stress on the specimen during the consoli-dation phase, and maximum axial strain that occurs during the cyclic phase of constant volume CDSS testing. Additional grades are also assigned to the tests based on unusual behaviors in the stress paths. Acceptance criteria based on the cumulative test scores are then proposed for “high” quality tests. The slope of the relationship between cyclic stress ratio (CSR) and number of cycles to liquefaction (NL) is influenced by the exclusion of tests using the acceptance criteria, even though the excluded tests were of sufficient quality to have been included in most published studies. 

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3. Excess Pore Pressure Generation and Liquefaction of Gravelly Soil

   https://doi.org/10.1061/JGGEFK.GTENG-13721  

   Jana, Amalesh; Stuedlein, Armin W (December 2025, Journal of Geotechnical and Geoenvironmental Engineering)

   This study outlines a probabilistic cyclic shear strain-based procedure for the determination of the minimum shear strain, γcl, required to initiate liquefaction in gravelly soils. The proposed formulation accounts for the influence of void ratio through the shear wave velocity and the grain size distribution through the coefficient of uniformity, Cu. Separate equations for γcl are derived considering four cyclic resistance models that rely on shear wave velocity as a measure of probabilistic liquefaction resistance. Similarities and differences in the resulting γcl for each of these models are identified. The accuracy and uncertainty of cyclic strain-based models in predicting liquefaction in gravelly soils are demonstrated using existing liquefaction case histories where grain size distributions are available. The excess pore pressure response of gravelly soils subjected to earthquake ground motions is evaluated using a subset of the available liquefaction case histories and the cyclic shear strain and energy-based frameworks and is compared to laboratory test specimens. Although the trends in excess pore pressure generation from critical layers in the case histories are comparable to laboratory-based responses, a greater rate of excess pore pressure generation is calculated for the field cases. The models presented in this study can help identify sites that have a high potential for ground failure when used together with other established models. 

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4. On Suitability of Element Tests to Represent Constitutive Response of Liquefiable Soils

   https://doi.org/ascelibrary.org/doi/abs/10.1061/9780784480779.227  

   Manzari, M.T.; Yonten, K.Y. (July 2017, Sixth Biot Conference on Poromechanics)

   Calibration and validation of constitutive models and numerical modeling techniques used in analysis of soil liquefaction and its effects are often based on extensive comparisons with the results of element tests and centrifuge experiments. While good quality experimental data are available to understand and quantify the stress-strain-strength response of liquefiable soils in monotonic and cyclic drained/undrained element (triaxial and direct simple shear) tests, the results of these experiments are often less repeatable when the soil approaches liquefaction state and relatively large deviatoric strains suddenly develop within a few cycles of loading. The main source of these less repeatable patterns of soil behavior appears to be instability rather than the attainment of a state of material failure. The goal of this paper is to investigate the role of instability on the stress-strain response of liquefiable soils by using a critical state sand plasticity model that is enriched with an internal length scale representing the potential shear bands that may develop during monotonic or cyclic loading conditions. Through a series of numerical simulations, it is shown that the global stress-strain response measured in the element tests is a good approximation of the soil constitutive response before an unstable condition such as shear banding or liquefaction develops in the soil specimen. 

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5. Stress-strain behavior of Ottawa sand in cyclic direct simple shear and modeling of cyclic strength using Artificial Neural Networks

   https://doi.org/10.1016/j.soildyn.2022.107585  

   Lbibb, Sarra; Manzari, Majid T. (January 2023, Soil Dynamics and Earthquake Engineering)

   The stress-strain behavior of Ottawa F65 sand is investigated through an extensive series of constant volume stress-controlled cyclic direct simple shear (CDSS) tests performed at different densities, overburden pressures, and static shear stresses prior to cyclic shearing to quantify their effects on the cyclic strength of Ottawa F65 sand. Results of the CDSS tests are used in the constitutive model calibration exercise for the Liquefaction Experiments and Analysis Project (LEAP-2022). The collected database of CDSS tests is used to develop an Artificial Neural Network (ANN) model capable of predicting Ottawa F65 liquefaction strength for a specified set of relative density, overburden pressure, static shear stress ratio, and cyclic shear stress ratio. After training, validation and testing, the ANN model is further assessed using blind prediction of the liquefaction strength in new CDSS tests for a relative density and overburden stress that are not available in the training dataset. CDSS tests under similar conditions were then carried out in the laboratory for validation of the ANN model. The comparisons of the predictions with the experimental results have demonstrated the ANN model predictive capability for liquefaction strength and its sensitivity to changes in relative density, overburden stress and cyclic stress ratio. 

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