Evaluation of liquefaction-induced lateral spread displacement based on ensemble learning

Liquefaction-induced lateral spread is a kind of ground deformation caused by soil liquefaction, which is a danger to houses, roads and other infrastructures. In order to systematically investigate the influence law of different parameters on lateral displacement, this paper establishes a numerical model of the seismic responses of gently sloping grounds through the open-source finite element software OpenSees and carries out a large number of calculations considering various working conditions. Based on the calculation results, eXtreme Gradient Boosting (XGBoost) and random forest (RF) regression are used to build the proxy models for lateral spread displacement prediction. The finite element model was verified by using the multiple VELACS No. 2 centrifuge experiments. Finally, the model was interpreted using SHapley Additive exPlanation (SHAP) method. The results of the model training showed that both models were able to achieve a good fit to the numerical calculation results, with the RF model having a smaller prediction error for the centrifuge experiments. The model interpretation results showed that the modified cumulative absolute velocity (CAV₅) was the most important input variable in the model, and the importance of ground slope (S), relative density (D_r) and thickness of liquefiable soil layer (H_L) was relatively high. In addition, the influence of each parameter on the lateral displacement is consistent with the actual situation, reflecting the rationality of the model prediction process. In addition, the results showed that there is a threshold for the modified cumulative absolute velocity (CAV₅) and Arias intensity (I_a) that leads to a significant increase in lateral displacement. The thresholds of CAV₅ and I_a are 1.3 g s and 1.0 m/s, respectively. These thresholds are in good agreement with the thresholds for triggering the overall initial liquefaction of the soil layer determined by related studies, which provides a reference for the evaluation of liquefaction-induced lateral displacement.