The detection of abandoned mineshafts by railway track bed using transmitted seismic waves using broadside shot gathers

The practical challenges of mineshaft detection under railway
embankments are discussed, together with typical mineshaft properties
over the centuries. The paper focuses on the broadside shot seismic
transmission method to detect abandoned mineshafts, with the potential to
be used in the vicinity of embankments. A numerical model was developed,
using a new type of absorbing boundary condition, which is referred to as
the Recursive Integration Perfectly Matched Layer. From a series of
simulations using this model, a series of practical outcomes were
identified regarding the feasibility of the broadside seismic
transmission method. These include the layout of the geophones, the
frequency of the shot source together with ways of improving the signal
to noise ratio. The results from a field trail in East Lothian, Scotland
are compared with the output from the numerical model and good agreement
was identified.