Analysis and evaluation of coral reef integrity based on borehole camera technology

At present, very few drilling surveys have been conducted on coral reefs, and comprehensive geological info on coral reefs is difficult to obtain. However, research on coral reefs is of great importance to development and exploitation of maritime resources. In the survey of Chenhang Island in Paracel (Xisha) Islands, we applied the digital borehole camera technology the first time in China, which resulted in a large amount of first-hand geological data. We utilized the rock mass integrity index (RMDI) method in our analysis of coral reef integrity, and the value of coefficient α in the RMDI was determined to evaluate the size effect of cavities on coral reefs. We then developed the correlation between RMDI values and coral reef integrity with references to the rock mass classification standard, which enabled the engineering evaluation of coral reef integrity. By statistical analysis of camera data gathered along the CK2 borehole for approximately 1-km length, we performed an integrity evaluation of the entire borehole length using the RMDI classification and created a coral reef stratum development diagram that was consistent with the actual cores. The results indicated: (1) the RMDI is a feasible approach for the analysis of coral reef integrity, (2) the classification system based on RMDI is feasible in the integrity evaluation of coral reefs, (3) the values of coral reef integrity obtained using the RMDI method are accurate, and (4) borehole camera survey and statistical analysis are important in the study of coral reefs.