Research on the Resistance of High-Low Leg Transmission Towers to Surface Horizontal Deformation in Mining Affected Areas

In order to evaluate the impact of mining-induced surface deformation on the safety of transmission towers with high and low legs， this study investigates a typical 220 kV tower. Finite element models of the tower were established for both equal-leg and high-low leg configurations （with a 2 m leg height difference）. The influence of types and directions of horizontal surface deformation on the force variation characteristics of the tower structure was studied and analyzed， and the capacity of the tower to resist surface horizontal deformation was obtained. The results indicate that buckling of the primary or secondary X-bracings or diaphragms is the primary failure indicator under horizontal surface deformation. The tower's resistance to deformation in oblique directions （30°， 45°， 60°） is significantly lower than in the 0° or 90° directions， with the 60° direction exhibiting the poorest deformation resistance， only 21.8%-29.9% in the 0° direction and 18.1%-31.4% in the 90° direction. Furthermore， the tower's resistance to tensile deformation is lower than its resistance to compressive deformation. The high-low leg tower exhibits significantly lower resistance to surface horizontal deformation than the equal-leg tower under the same conditions， with a maximum difference of 40.0%. Therefore， when constructing high-low leg transmission towers in mining areas， the direction of surface deformation must be considered， and the anti-surface-deformation performance， particularly in oblique directions， requires specific evaluation.