Energy-based analysis of seismic damage identification and failure mechanism of bedding structure slopes using VMD-HT and instantaneous energy spectrum

Abstract

The accurate identification of the characteristics of joints, fractures, extensions, and slips within the slope under earthquake action is essential for understanding the potential failure modes of bedding rock slopes (BRS). In this paper, an innovative method for separating low-frequency seismic response signals (LFSRS) and high-frequency rock damage signals (HFRDS) using VMD-HT was developed, and an index for identifying BRS internal damage using HFRDS was proposed. Three typical BRS cases types-blocky, soft-hard interbedded, and weak intercalation-included in the high seismic intensity area of southwest China were selected to prove the proposed method for separating damage signals. The seismic discrete element numerical modeling was utilized to analyze the crack development and damage evolution characteristics, and illustrate the patterns of seismic instability evolution in BRS. Through a comprehensive analysis of the time-domain, frequency-domain, and time–frequency domain signal characteristics, it was confirmed BRS exhibit a combination of LFSRS and HFRDS resulting from rock structural plane cracking and rock block collisions. The damage identification capability of the peak of marginal spectrum amplitude was assessed for LFSRS, proving its capability in locating damage and evaluating the distribution of seismic energy but failed to detect minor damage and determine the timing of damage occurrence accurately. The instantaneous high-frequency energy level index (IEL_h) was introduced using HFRDS, enabling the identification of crack initiation and propagation locations within the slope and pinpointing the moment of crack appearance. A quantitative relationship between the IEL_h index and the damage degree was finally established. The findings of this study are highly significant for the in-depth exploration of the seismic failure mechanism of the BRS landslide from the perspective of energy-based transmission characteristics.