## 4 Case Analysis
### Data Processing  
Digital image processing is performed on the video image acquired by this technology; after the coordinates of the center of the circle in the image are determined, the origin of the computer coordinate system is transformed to the center of the circle image. The video images of different depths are tangentially expanded, and the images are radially expanded to form the borehole wall expansion image as shown in Figure 9. The horizontal direction of the image in Figure 8 represents the depth of the borehole, and the depth of the borehole gradually increases from left to right. The left side of the image represents the rock wall image at a depth of 28.5 m, and the right side of the image represents the rock wall image at a depth of 29.5 m. From top to bottom, Figure 8 represents that the borehole is unfolded from north to anticlockwise, that is, the borehole image represents the rock wall azimuth image of \"North West South East North\" borehole from top to bottom.  
During the analysis of the hole wall characteristics of the image, the image was divided into 360 \(\times\) 1000 basic units, that is, the number of scanned lines in the borehole rock wall  
Figure 8: Partial data collected. (**a**) Video image screenshot of rock wall, (**b**) rock wall acoustic wave scanning data.  
Figure 9: Rock wall expansion image.  
was 360, and the angle between the two adjacent scanning lines was \(1^{\circ}\). In the borehole depth direction, the distance between the two adjacent foundation units was 1 mm. In this paper, the image of hole wall texture feature response function TF and the hole wall integrity feature response function IF were calculated, respectively. The results of the image after the matrix are shown in Figure 10a. The results of the image corresponding hole wall integrity feature matrix are shown in Figure 10b. The acoustic scan data acquired using the present technique was transformed into matrix information and f\({}_{1}\) = 0.2 MHz, f\({}_{2}\) = 2 MHz are selected. The acoustic characteristic function was calculated separately for the transmit signal and the received echo signal respectively. The acoustic features of the hole wall at 28.5-29.5 m are shown in Figure 11a. The profiles of the hole wall at 28.5-29.5 m are shown in Figure 11b.  
After completing the calculation of hole wall texture feature response function TF, IF, hole wall acoustic feature response function AF and CF, the matrix to form hole wall texture feature, hole wall integrity feature, hole wall acoustic feature and hole wall profile feature image, the four images were fused according to the weights of 0.25, 0.25, 0.25, 0.25 and 0.25 to reconstruct a new borehole rock wall expansion image, as shown in Figure 12a. Subsequently, the borehole rock wall reconstruction image FI, considering a variety of hole wall features, was binarized to form a binary image, as shown in Figure 12b. From the binary image, we can distinguish between the weak interlayer and realize the identification of the weak interlayer. The black area is used to indicate the weak interlayer in the geological borehole of the landslide, and the white area is used in the landslide geological borehole, so as to provide a reference for judging the sliding surface of the landslide. The technical method in this paper shows that there is a weak interlayer at  
Figure 11: Acoustic scanning characteristics of rock walls. (**a**) Hole wall acoustic feature image, (**b**) hole wall contour feature image.  
Figure 10: Rock wall optical image characteristics. (**a**) Hole wall texture feature image, (**b**) hole wall integrity feature image.  
the borehole depth of about 29.1 m, which needs special attention. The thickness of the sandwich is about 5 cm.