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Key research themes
1. How can probabilistic reliability methods improve the assessment of soil liquefaction potential compared to deterministic approaches?
This research theme focuses on developing and applying probabilistic reliability-based methods to quantify and better capture the uncertainties inherent in soil liquefaction potential evaluation. Traditional deterministic methods often rely on safety factors that do not provide liquefaction probabilities, limiting risk-informed decision-making. Reliability analyses incorporate variabilities in soil properties, seismic loading parameters, and testing uncertainties to estimate liquefaction probabilities, thus enabling more nuanced hazard assessment and engineering design.
Key finding: Developed a reliability-based framework using advanced first-order second-moment (AFOSM) methods to compute liquefaction probability as a continuous function of factor of safety, based on analysis of 190 field records from... Read more
Key finding: Applied the first-order second-moment (FOSM) probabilistic method to a large dataset of 1510 boreholes in Kathmandu Valley, incorporating uncertainties in seismic parameters (peak ground acceleration, earthquake magnitude)... Read more
Key finding: Conducted a comparative reliability analysis incorporating uncertainties in Standard Penetration Test (SPT) measurements alongside various empirical liquefaction evaluation methods (Seed et al., Japanese Highway Bridge... Read more
2. What role does soil spatial heterogeneity and field property variability play in influencing liquefaction resistance and hazard assessment?
This theme explores how intrinsic spatial variability and heterogeneity of soil properties affect the mechanical behavior under seismic loading and consequently the liquefaction potential. Traditional deterministic analyses often assume uniform soil properties, which can underestimate failure probability and liquefaction-induced deformation. Experimental centrifuge studies combined with advanced stochastic numerical simulations investigate how variability in properties such as Standard Penetration Test N-values, shear wave velocity, and internal friction angle modify pore water pressure development and failure mechanisms.
Key finding: Demonstrated through centrifuge experiments and stochastic finite element modeling that heterogeneous soils develop greater excess pore water pressure under cyclic loading compared to homogeneous soils of equivalent average... Read more
3. How do advanced laboratory and field testing techniques, including shear wave velocity and cone penetration tests, contribute to improved evaluation and mapping of liquefaction potential?
This research area centers on refining liquefaction potential assessment through integration of geotechnical field testing methods such as Shear Wave Velocity (Vs), Standard Penetration Test (SPT), Cone Penetration Test (CPT), and geostatistical mapping tools. These methods offer more direct, continuous measures of in situ soil properties affecting liquefaction resistance. Correlations between Vs, peak strength, soil grading (uniformity coefficient), and cyclic resistance ratios facilitate more accurate identification of liquefiable layers. Spatial interpolation techniques such as kriging enable development of liquefaction potential maps identifying vulnerable zones for infrastructure planning and hazard mitigation.
Key finding: Used shear wave velocity measurements combined with Seed and Idriss simplified procedure to evaluate liquefaction potential at six borehole sites near Kalyani, India. This method was preferred over SPT/CPT due to... Read more
Key finding: Conducted paired CPT and SPT tests in six locations in Sanur area, Bali, analyzing soil resistance against liquefaction with respect to earthquake magnitudes Mw=4.0 and 5.0. Results showed soil layers remained safe at Mw=4.0,... Read more
Key finding: Integrated multiple CPT-based empirical liquefaction models with geostatistical techniques—specifically kriging interpolation within a GIS framework—to spatially estimate and map liquefaction potential at the Airport of... Read more
Key finding: Through undrained triaxial testing augmented by shear wave velocity measurements on sands, silty sands, and silts with varying grading coefficients (Cu), established that the ratio of initial shear wave velocity (Vs0) to peak... Read more
4. What is the influence of soil saturation degree, particularly partial or unsaturated conditions, on liquefaction resistance and triggering?
Research in this theme examines how variations in soil saturation, including partial saturation and induced desaturation, alter liquefaction resistance by modifying pore water pressure generation, matric suction, and volumetric stiffness during cyclic loading. Laboratory cyclic triaxial tests on partially saturated sands demonstrate increased liquefaction resistance compared to fully saturated states. Theoretical interpretations based on equivalent viscous damping and volumetric strain mechanisms explain these effects, suggesting that partial saturation can be a practical mitigation strategy and must be accounted for in liquefaction models.
Key finding: Laboratory cyclic undrained triaxial tests on three types of fine-grained sands with varying degrees of saturation showed that liquefaction resistance increases markedly as saturation decreases. The study introduced an... Read more