Energy evolution and damage failure mechanism of coral sand grouted stone bodies under different stress paths

In practical applications, coral sand grouted stone bodies (CSGSB) may undergo multiple cycles of loading. To investigate the failure mechanism of CSGSB under different loading paths, this study conducted triaxial compression tests under three different loading paths. Using a combination of supervised and unsupervised learning algorithms, a Kmeans–SVM clustering model was developed. Acoustic emission (AE) non-destructive testing technique was employed to analyze the internal energy evolution and damage failure mechanisms of CSGSB. The results showed that increased loading path complexity led to lower peak strength and greater deformation at failure. Under stepwise cyclic loading, the specimens exhibited creep-like cumulative deformation characteristics. During cyclic loading, the energy density showed a distinct quadratic growth trend with increasing axial stress, accompanied by a linear energy storage behavior. Path-dependent differences in energy storage capacity were observed, with stepwise cyclic loading being less favorable for elastic energy accumulation. The AE signals demonstrated a clear Kaiser effect during cyclic loading, and clustering results from the Kmeans–SVM algorithm indicated an increasing proportion of shear microcracks with higher cycle numbers and confining pressures. The evolution trends of the damage variable under different stress paths were generally consistent, while more complex paths led to reduced axial load-bearing capacity and increased internal damage. These findings enhance the understanding of the damage evolution mechanism of grouted coral sand materials, and provide a methodological and data-driven basis for disturbance response analysis and damage warning studies of grouted structures in island and reef engineering.