Mining-induced ground deformation in tectonic stress metal mines: A case study

• Tectonic stress metal mines may be subjected to regional horizontal movement.
• Stress release will make the ground deformation undergo significant changes.
• Failure mechanism in deep rock mass can be revealed by time–displacement curves.

In situ monitoring data of ground deformation in the western area of Chenchao Iron Mine were collected over eight years. Results were analysed to conduct a preliminary investigation into the ground movement induced by underground mining: (1) in the northeastern area, the ratios of horizontal to vertical displacement increase gradually, and the horizontal displacement may be as much as an order of magnitude larger than the vertical displacement at a large distance, which induces regional horizontal movement. Curves of the ratio of horizontal to vertical displacement with respect to time can be categorised as: fluctuation-, fallback-, convergence-, and increase-types; (2) in the mine road, stack-site, and southern area around the high-voltage tower, ground deformation can be divided into two stages: stable deformation and rapid deformation. While in the southeastern area of the transport tunnel, service shaft, and road tunnel, it can be divided into three stages: stable deformation, rapid deformation, and subsequent stable deformation. Three categories are found in the time–displacement curves: folding-, S-, and linear-types. (3) The ground deformation of the footwall underwent a significant change in January 2010, because the large horizontal tectonic-stress in the mine was released at that time. Surrounding rock masses were subjected to toppling deformation along the major structural plane in the northeastern area, while tensile deformation occurred perpendicular to the major structural plane in the northern area.