Automated rock slope monitoring system has been established and the characteristics of slope behavior is analyzed with consideration of field rock structure by virtue of borehole information of joint orientations and positions acquired from Discontinuity Orientation Measurement (DOM) drilled core log. Regarding the core axis as a scanline, structural properties of rock mass has been assessed. Anticipated failure modes of rock slope and the regional instability is inspected by tracking down the hazardous joint planes the traces of which are projected on the cut-face. Formation of potential wedge blocks and their stability are also analyzed. Cross section has been set to include DOM borehole and traces of failure-inducing joint planes. These information of rock structure and the location of risky joint planes is used, together with the monitoring data acquired from the inclinometer installed inside DOM borehole, to illustrate the aspect of internal slope behavior and to delineate the detailed triggering mechanism of slope movement.
Structural characteristics of rock mass for the construction of cut-slope has been generally investigated by performing window or scanline survey on the exposed rock mass and/or by implementing borehole image-taking instruments to acquire the orientations of discontinuity planes (Haller & Porturas, 1998; William et al., 1997; Hornby et al., 1992). Recently, Yoon et al. (2003) and Cho et al. (2004) developed DOM (Discontinuity Orientation Measurement) drilling system which can determine the relative positions and orientations of discontinuity planes intersecting the drilled core log. Combined information of both orientation and position of each discontinuity constitutes the plane equation in three dimensional space and the joint trace map can be constructed by numerically projecting discontinuity planes on the anticipated cut-face of rock slope. To elucidate the applicability of DOM borehole information for rock slope monitoring potential modes of failure and the anticipated slope behaviour have been investigated. Joint planeswhich may cause plane or toppling failure are inspected and their traces on the cut-face are envisioned by manipulating the plane equations of both relevant joints and cut-face. Formation of potential blocks on the cut-face is also analyzed. Directions of joint intersection lines are calculated and their sliding potentiality with respect to the orientation of cut-face and the internal friction angle of joint plane is examined. By tracking down the joint planes which mutually intersect the block base-forming joint planes on the slope surface, three dimensional geometry of individual block has been precisely defined. This process is repeated to detect every possible potential block and the posture of block formations inside the slope model is depicted. Inclinometer has been installed inside DOM drilled borehole and slope behaviour has been monitored. To illustrate the significance of internal structure on the behaviour of rock slope cross section, the direction of which is normal to the slope face, has been set and the posture of sliding joints and the extent of tetrahedral blocks on the section are algebraically calculated. Information of rock structure has been efficiently used for more realistic interpretation of monitoring data.
