Abstract:
Conventional engineering geological survey methods are often difficult to apply when studying high and steep rock slopes. In such conditions, the use of drilling equipment is difficult and even dangerous, especially when there are weak, strongly weathered sections on the slopes, creating a potential danger of self-collapse of rock fragments. In many cases, the slopes are close to roads or railways, a circumstance that creates extra danger.
The possibilities for mapping zones affected by weathering and secondary alteration in the near-surface parts of rock complexes by the application of ERT (Electrical Resistivity Tomography) method are presented. The high efficiency of this non-invasive method is based on the large differences between the electrical resistivity values typical for the unaltered rock varieties and for those affected by weathering processes. The sharp differences in ionic conductivity are due to the presence of a high percentage of gas or liquid phase between the altered particles, as well as to the presence of fine-grained, fine-dispersed or decomposed to clay materials.
In the presented article are illustrated the results of a geoelectrical survey for mapping weathered zones in the upper parts of rock slopes along the route of the Struma highway, Southwestern Bulgaria. The results of the study are of great practical importance for the development of a project for optimal strengthening and securing of the hazardous slopes, which has been successfully implemented.