The electrical resistance measurement system (ERMS) was tried to be developed. The first in-situ applications were carried out in A6 panel in GLİ underground coal mine. As perpendicular to the pillar face, two parallel boreholes with 4 m long and interval 30 cm were drilled. The copper plates with a width of 200 mm and a thickness of 0.5 mm was wrapped on the measuring rod with 50 cm intervals and also soldered with copper wires. Then two rods were separately inserted into boreholes named as ERMS-#. In this way, 5 stations were installed with 5 m intervals. Measurements were carried out by ohmmeter using each electrical wire coming from the copper plates located at the same depth of boreholes. ERMS values measured on pillar subjected to dynamic loading due to longwall mining operations were shown that there were unstable in the first 2.5 m region of the pillar side.
The electrical permittivity depends on the degree of freedom of the electrons or ions of the materials. Metallic materials are conductive due to their free orbital electrons. On the other hand, it is known that rocks behave like insulator materials because they show very high resistance to electron transfer. If a rock material is electrified, electric current cannot flow easily. Electrical conductivity in water-free or dried rock materials can be achieved at very high voltages such as 25-50 kV. However, electrical potential differences in rock materials containing water can occur even at normal voltages (110-220V). Electrical resistance behaviors may differ depending on the rock material properties and water content differences. Water is an important parameter that allows free movement of ions. Differences in water concentration in the rock cause uneven distribution of free ions in the rock material. Therefore, different parts of the same rock mass may show differences in electrical conductivity. Consequently, electrical resistance is an important material property that depends on the type of material being tested.
The water content of the rock material is respectively; it depends on material properties such as porosity, permeability, mineralogical and structural properties. In particular, discontinuities act as water passageways in the rock mass and contain more water than the bedrock blocks. This means that there are more free ions in and around the discontinuities, so low electrical resistance values in these sections are expected. Depending on this general structure, the explanations of which are given, the electrical conductivity measurement method today is respectively; It is used in mineral exploration, cavity localization, exploration of water-bearing formations and many other engineering applications. In a material that allows electric current to pass, the resistance (ohm) can be calculated by dividing the electric current flow rate (ampere) by the electric potential difference (volts) between the ends of the material.
