Measuring the orientations of hidden subvertical joints in highways rock cuts using ground penetrating radar in combination with LIDAR

Mapping discontinuities in rock cuts and measuring their orientations is crucial in assessing the stability of rock masses. This can be done usually using manual methods such as scanline or advanced techniques such as LIDAR. However, these methods are used only to map exposed discontinuities which may cause underestimation for slope stability. Accordingly, ground penetrating radar (GPR) has been recently used to detect such hidden discontinuities.;The used 400 MHz monostatic GPR antenna was significantly able to detect and map hidden subvertical joints within 4 m depths in five sandstone highways rock cuts and within 3 m depths in two ignimbrite highways rock cuts in the State of Missouri. Manual 2D migration was done to estimate, in 2D and 3D radiograms, "the slope face-perpendicular depths" which was measured from three coplanar etched points, "the three index points", at each rock cut surface to the corresponding points on each plane of the detected subvertical joints.;The orientations of the detected hidden joints were then determined based on the 3-point equation and using the calibrated LIDAR coordinates. Some of these measurements were confirmed by very close-results of field verification measurements. The results of this GPR-and-LIDAR based investigation demonstrate that our new proposed approach using these techniques is straightforward, understandable, and can be valuable in some rock engineering applications and rock cuts design in terms of the orientations of joints, in addition to the number of joint sets which may build a more clear view about the rock cut stability than before.