Abstract: The mining of metal mines by sublevel caving often results in excessive surface deformation and damage to the buildings on the ground. Scholars mostly study the boundary of the acceptable deformation (movement curve) and the angle of the boundary of the acceptable deformation on the surface of the metal mine. The curve is the boundary of area where normal living or use is not ensured due to damage of surface buildings or structures, but the area outside of the line is still affected, which is lack of studies on it. Therefore, studying mining influence range and limit angle is of great significance to mining theory. Taking the west area of Chengchao Iron Mine in Ezhou, Hubei as an example, based on the results of monitoring data of horizontal surface displacement in the past 4 years (from May 2016 to May 2020), measuring error is taken into account and the threshold value is set. The influence curve can be obtained through Kriging interpolation, and the limit angle is determined. Comparing with the movement curve and moving angle, the results show that there is a sudden change in the range of the influence curve of the hanging wall, and the mining level plays a dominant role in the extension of the influence curve. The influence curve can be a warning sign of the extension of the boundary of the dangerous deformation zone. A large structural crack will cause a wide range of influence curve in local footwall area, the limit angle outside the structural crack has the same change pattern as the movement angle. The difference in the mining boundary of different levels has an important impact on the limit angle in the hanging wall, which indicates that the boundary difference effect of the upper and lower layers should be considered when studying the limit angle and deformation prediction caused by metal mining. The stability of the limit angle depends on whether the mining level has major changes. Due to the existence of the pillar, the limit angle in the end area is about 6o smaller than the movement angle.

Key words: mining engineering, metal mine, the influence curve, limit angle, the boundary of the acceptable deformation, movement angle