TEM response characteristics of borehole in goaves of old coal mines

The transient electromagnetic (TEM) method is widely used in coalfield hydrogeological exploration and goaf investigation in China. However, due to the characteristics of the method itself, the vertical resolution of the ground device is low, and thus it is impossible to realize the fine detection of goaves. In a goaf exploration project of a coal mine in Shanxi Province, a simple goaf model of coal measure strata was established according to the study on cores and logging curves, as well as previous experience of electrical exploration. Based on this, numerical simulation was conducted for the ground TEM response of goaves with and without water in a homogeneous half-space and the ground-well TEM response of three-dimensional horizontal thin plates. As confirmed by the characteristics of the ground and ground-well TEM response of goaves in some practical cases, the ground-well TEM has high vertical resolution, which provides an idea for fine exploration of goaves.