Evaluation on earthquake-induced cyclic weakening of liquefiable ground using shear wave velocity

Strong earthquake loadings will cause the generation of excess pore water pressure in saturated sandy soil grounds (i.e. the cyclic weakening) until the triggering of soil liquefaction, and the reliable evaluation of the cyclic weakening is crucial for evaluating the seismic performance of foundations and superstructures. A new term of cyclic resistance ratio for weakening ( CRR r u ) is defined as the cyclic stress ratio ( CSR ) required for soil to generate a specific excess pore water pressure ratio ( r u ) under a given number of loading cycles ( N ). Based on existing liquefaction resistance characterization models, a shear wave velocity-based cyclic weakening resistance characterization model (abbreviated as cyclic weakening model) of sandy soils was proposed. An engineering case study was conducted to illustrate the applicability of the proposed cyclic weakening model at a hydraulic power plant site. Firstly, the contour maps of depth-weighted average excess pore water pressure ratio for both unimproved and stone column-improved grounds were derived based on the proposed cyclic weakening model and field shear wave velocity. Secondly, the field response of excess pore water pressure in both unimproved and stone column-improved grounds was monitored during the 2022 M w 6.6 Luding earthquake. Using the derived contour maps, the excess pore water pressure ratio during this earthquake was predicted, and the proposed model was preliminarily validated by comparing the predictions with the field-monitored data.