Experimental Study on Damage Behavior of Porous Coral Limestone from the Zhongsha Islands, South China Sea

The damage characteristics of coral limestone are of great significance for guiding the design and construction of offshore engineering such as submarine tunnels and pipelines. The mechanical properties and damage behavior of coral limestone collected from the Zhongsha Islands, South China Sea were investigated based on the results of uniaxial compression tests. A theoretical porosity calculation method was put forward and applied to the coral limestone with a large number of closed internal pores. The failure characteristics of the coral limestone are very different from those of terrestrial rocks because the strength decreases gradually after failure. The threshold stresses of coral limestone were calculated based on the uniaxial compression tests and compared with that of terrigenous rocks. The crack initiation stress is 39-56% of peak strength, similar to that of most terrigenous rocks. The crack damage stress is 70-100% of peak strength, differing greatly from most terrigenous rocks. Coral limestone presents a pattern of shreds after failure due to its unique biological pore structure. In this paper, a new damage variable was proposed to quantitatively analyze the damage behavior of coral limestone. Because coral limestone contains numerous original pores, damage occurs to a large extent in the unstable cracking stage. Good linear correlations were identified between each threshold stress and peak stress, and corresponding empirical formulae were put forward. This paper analyzed the damage characteristics of coral limestone from the Zhongsha Islands, which can provide reference for damage analysis of other porous brittle rocks.