Compressive Mechanical Behavior of Seawater Coral Concrete Subjected to Axial and Biaxial Loading

With the advancement of marine engineering, coral concrete—comprising coral coarse aggregate, coral sand, and seawater—has garnered increasing research interest. To further investigate its compressive mechanical behavior under axial and lateral biaxial stress states, a total of 9 prismatic specimens under axial loading and 45 cubic specimens under biaxial loading were prepared, encompassing three strength grades (C20, C30, and C40) and five lateral stress ratios (0, 0.25, 0.5, 0.75, and 0.9). The failure modes and corresponding axial and biaxial stress–strain curves were meticulously recorded. The axial mechanical response was systematically analyzed, leading to the establishment of a compressive damage constitutive model based on the Weibull distribution. Additionally, the influence of the lateral stress ratio on both peak stress and peak strain was examined, and multiple biaxial failure criteria were formulated. Experimental results reveal that the failure modes of coral concrete specimens are analogous to those of natural coarse aggregate concrete and are significantly affected by the lateral stress ratio. Specifically, an increase in the lateral stress ratio results in higher peak stress, while the absolute value of peak strain exhibits a linear variation. Finally, the proposed axial damage constitutive model and the biaxial failure criteria are rigorously validated against the experimental data.