Coupling effects of natural fibre reinforcement and particle size on liquefaction of sands via strain- and energy-based cyclic failure criteria

Investigating the liquefaction mechanism in sands reinforced with randomly distributed natural fibres poses a substantial challenge in geotechnical earthquake engineering. This challenge becomes particularly pronounced when utilising cyclic direct simple shear (CDSS) tests to closely replicate earthquake loading conditions. In this study, a unique approach is taken to address this challenge by examining the coupling effects of fibre reinforcement and particle size on the cyclic behaviour of sands. Furthermore, the research investigates the cyclic simple shear responses of two categories of sandy soils with distinct mean particle sizes (D₅₀ = 0.63 and 1.00 mm) mixed with sisal fibre content (Fs) ranging from 0% to 0.6%. The samples underwent testing using a CDSS apparatus at three different cyclic stress ratios (CSRs = 0.13, 0.15 and 0.20). The outcomes of CDSS tests indicate that the content of fibres, along with the mean grain size of sands, significantly influence the cyclic liquefaction characteristics of tested specimens. Thus, the examination of the current findings confirms that the normalised dissipated energy parameter stands as a reliable indicator for articulating and forecasting the cyclic liquefaction phenomenon of sand–sisal fibres mixtures. In addition, novel correlations have been developed to forecast changes in the number of cycles (N), cyclic resistance ratio (CRR) and maximum normalised dissipated energy (W_nmax) based on the examined parameters (Fs, D₅₀ and CSR). The agreement between the predicted and measured characteristics affirms the effectiveness of these proposed relationships in reliably predicting N, CRR and W_nmax characteristics.