Research on surface movement and deformation characteristics of loess gully landform in Northern Shaanxi

In order to study the surface movement and deformation characteristics of the collapsible loess gully landform in the northern Shaanxi mining area in the middle reaches of the Yellow River Basin, the N1212 working face in the loess gully area of the Ningtiaota Mine has been systematically monitored for surface subsidence to analyze the high-intensity mining conditions Deformation characteristics of the ground surface subsidence, determine the maximum surface subsidence speed and the maximum subsidence speed lag angle, surface movement time and dynamic surface movement parameters. The results of the study show that the discontinuous deformation and destruction of the surface in high-strength coal mining in the collapsible loess layer in northern Shaanxi are severe, and the loess surface is easily affected by the combined effects of movement and deformation and topographic conditions, resulting in uneven settlement. Under high-strength mining conditions, the surface movement and deformation are severely developed , The maximum surface subsidence value is 5255 mm, the maximum horizontal movement value is 2680 mm, the maximum subsidence speed is 187.4 mm/d, the maximum subsidence coefficient of single coal seam mining is 0.63, the maximum subsidence coefficient of oblique repeated mining is 0.84, the active period is about 55 d, and the period of subsidence is about 55 d. The amount accounts for 97% of the total subsidence, the maximum lagging distance of the down-town velocity is 74 m, and the maximum lagging angle of the sinking velocity is 67°. The above results verify that in the high-intensity mining of shallow coal seams, the surface subsidence is proportional to the geological mining factors when the ground subsidence is severe, the activity period is short, and the mining is repeated. The surface deformation of high-intensity mining in the valley terrain has the characteristics of fast speed, large collapse and heavy damage.