Abstract: To assess the engineering application potential of coral mud, a model test was conducted on cracking in the surface layers of polyvinyl alcohol (PVA) fiber-modified coral mud using particle image velocimetry (PIV) technology. The displacement and velocity fields of the coral mud surface layer were obtained, revealing the cracking and crack inhibition mechanisms from the perspective of multi-physical field interactions and energy dissipation. The interaction mechanisms between multi-physical fields and soil moisture evaporation, shrinkage, and cracking were discussed, providing a new perspective on crack dynamic behavior. The results indicate: (1) Under gravity, the trajectories of surface particle movement in the coral mud surface layer show a clockwise vortex-like contraction direction. Soil particles in the coral mud surface layer reach maximum velocity at crack locations. As cracks initiate, develop, and stabilize, particle velocity accelerates, peaks, and then decelerates. (2) Carbonate mineral components in the coral mud undergo chemical hardening, crystallization, and cementation. Cementation occurs between PVA fibers and coral mud particles and between coral mud particles, enhancing the strength of coral mud. Optimal performance occurs at a fiber content of 0.5%, with minimal cracks on the coral mud surface. (3) Coral mud cracking occurs in three forms: tensile failure, shear failure, and tensile-shear mixed failure. (4) From the perspective of multi-physical field interactions and energy dissipation, the mechanisms of cracking and crack inhibition in the coral mud surface layer are elucidated, offering new insights into the interaction between multi-physical fields and soil evaporation, shrinkage, and cracking are proposed. The interaction of moisture, displacement, velocity, and stress fields during soil cracking collectively influences the formation and development of soil cracks. These interactions form a complex system affecting soil stability and mechanical behavior.

Key words: coral mud surface layer, fiber modification, PIV technology, shrinkage and cracking, multi-physical fields, crack inhibition mechanism