The mechanism involved in deep-seated landslide-debris flow disaster chains has been studied for many years, however, it is still not completely understood. This study aims to analyze the key factors that were involved and led to the geological disaster of Shaziba 62.0 m deep landslide-debris flow. Two extensive field investigations were conducted before and after the slope failure event. The study further used drilled cores, high-density resistivity method, and aerial photographs to obtain valuable insights into the disaster chain. It was found that opencast coal mining operations broke the locked segment of the front edge and heavy rainfall softened the slip zones along the faults. Mechanical calculations demonstrated that the coupling condition of the opencast coal mining and heavy rainfall triggered the landslide. A new evolution model was put forth to describe the complex mechanism of combining progressive retreat and tractive failure of hydraulic drive land-slide, which was governed by the bedding-plane rock layer. Surface runoff caused the mass of the landslide to liquefy throughout the sliding process, resulting in overlapping deposits, debris-flow-barrier-lake, and erosion. These new insights led to the indication of a different triggering mechanism of landslides-debris flows, as well as laid the foundation for the proposed physical and mechanical mechanism model based on progressive retreat soil-rock mixed landslides with an upper locked segment and lower weak interlayer under heavy rainfall.