Application of Borehole Camera Technology in Fractured Rock Mass Investigation of a Submarine Tunnel

Borehole camera technology can penetrate into the inner part of the rock mass, observe the characteristics of the fracture, measure the data of the fracture geometric parameters, and a reasonable statistical method is the key to analysis of structural characteristics of fractured rock mass. Based on the observation results of digital borehole camera technology, the principle and method of calculating the fracture parameters from borehole images are described. Taking the Qingdao Jiaozhou Bay Subsea Tunnel Drilling ZK3 as an example, the structure information revealed by borehole is obtained by borehole camera. The statistical analysis of geometry parameters is studied and the distribution of fracture is analyzed, including the dominant occurrence of calculation, aperture distribution and depth distribution etc.. The integrity index RWID of the borehole wall rock mass is established, and the integrity of the wall rock mass is evaluated according to this index. the main conclusions are as follows: (1) digital borehole camera technology provides an effective technical means for geological survey of fractured rock mass; (2) the evaluation index of RWID based on borehole wall integrity core length can reflect the integrity of rock mass, providing a good verification method for RQD method.