TDR technology was used to detect the cable faults in CATV industry, and it was firstly applied with geomaterials in the 1970s. This technology is employed in geotechnical engineering and environmental engineering recent decade.
You may take 1D radar as a early form of TDR, and you can read reference listed below or read "Introduction to TDR" if you want to know furthermore.
A. TDR Penetrometer Development
B. Landslide Monitoring
C. TDR Autmation: System Establishment and Programming
D. Electrical Conductivity Measurement Using TDR
E. Suspended Sediment Measurement Using TDR (Fig.1)
F.Subsidence Measurement Using TDR (Fig.2)
Fig.1 TDR concentration
Fig.2 TDR Subsidence monitoring
Here is a profile to introduce the main idea of the electrical properties of soils.
"Basic electrical properties of soils (PDF)"
Disaster Prevention Management
Study of Disaster Information Integration between Central Government and Local Government