The article analyzes how underground coal mining causes ground sinking, which harms the environment and structures. By using viscoelastic and random medium theories, the researchers studied the sinking boundaries of bedrock and loose soil. They found that bedrock sinking boundary is 1/4 of the pressure wave wavelength, while loose soil sinking boundary curves upward. The angle of sinking boundary in loose soil decreases from bottom to top, forming a convex curve. Combining both bedrock and loose soil, the overall sinking boundary is bowl-shaped. This study helps understand ground sinking and can support predicting future sinking in mines.