An image recognition method for the deformation area of open-pit rock slopes under variable rainfall

•An improved region growing segmentation method (IRGSM).•Deformation and failure characteristics of rock slopes in the time dimension.•The relationship between rainfall intensity, water content, pore water pressure, damage area and damage volume.•Analysis of failure mechanism of rock slope under variable rainfall. Due to human mining action, relatively fragile open-pit mine rock slopes are prone to instability induced by heavy rain. Accurately identifying the information and area of deformation features on rock slopes is a key step for landslide disaster warning and prevention. This study simulates the deformation process of a large and steep rock slope in Dexing City, Jiangxi Province, China, under a variable rainfall event. The test results show that 1) the increased deformation region has positive relationships with increasing pore water pressure and water content values for the open-pit mine rock slope affected by heavy rainfall. 2) The infiltration of variable rainfall on the rock slope softens the weak interlayers and leads to failure of the slope toe first. Due to the action of gravity, the middle and upper parts slide and fail in sequence. In addition, an improved region growing segmentation method (IRGSM) is proposed based on the combination of multipixel seed points and point cloud coordinates for the image recognition of the deformation area of open-pit mine rock slopes. An error comparison with the original region growing segmentation method (ORGSM) shows that the average identification error in the X and Y directions by the method is reduced significantly (6.56% and 5.32% in IRGSM; 13.37% and 11.29% in ORGSM). This method may be applied to identify rock slope deformation in complex scenes with high precision.