Research on Anti-Foundation-Displacement Performance and Reliability Assessment of 500 kV Transmission Tower in Mining Subsidence Area

The performance of resisting foundation displacement of typical single return circuit and double return circuit transmission towers under all kinds of load conditions including foundation horizontal displacement, foundation vertical uneven downward displacement were analyzed by finite element modeling. Results showed that stability failure of single steel angle represents tower's limit state under foundation displacement. The corresponding foundation displacement limits were calculated. And the towers' reliability were assessed by comparing the calculated earth surface deformation in advance to the towers' earth surface deformation permissibility. Result indicates that tower does not fail when foundation displacements are smaller than 0.5% of tower root distance. The assessment result revealed that under coal mining deformation conditions, complex foundation and measures adjusting the length of bolts between towers' legs and foundations can ensure all object towers' safety. The complex foundation is more effective than single foundation in resisting coal mining deformation.