Imaging And Charcacterizing Fractures In A Rock Slope

This paper describes that a Seismic reflection survey and logging were quite useful to image and<br>characterize fractures inside of crystalline rock slope.<br>Until now, rock slope stability has been qualitatively evaluated from the surface observation data on a<br>rock slope. However, it is very diflicult to estimate fracture extension inside of a rock slope only from the<br>surface evidence in quantity. The main feature contmlling the slope stability should depend on the spatial<br>distribution of fractures in a rock mass. For the first step to delineate the fractures in a rock slope, we<br>performed a seismic reflection survey and leggings.<br>A test site is located on Shikoku Island, western part of Japan. The rock slope consisted of schist, which<br>was hctured with a large number of joints and fissures. It was predicted to cause rock slide.<br>We set receivers spaced 0.5 meters apart in length and width lines along the slope surface. For imaging<br>the fractures oblique to the survey lines, we adopted pre-stacked depth migration technique. Some fractures<br>were imaged and detected in the interior of the rock slope. Locations and directions of the fractures were<br>consistent with the surface observation data.<br>leggings were carried out in a borehole drilled from the top of the slope body into the back side of the<br>surface. Borehole camera mapped thirty-six fractures. Besides natural gamma spectrum, temperature and<br>VSP characterized and revealed that all fractures were not open and conductive. We interpreted that the slope<br>would be stable.