GPR Measurements for Engineering Damaged Zone (EDZ) Investigation

As a part of underground research of intermediate and low level radioactive waste disposal site in Bataapati geophysical measurements were carried out after the excavation immediately and one year later for determination of extension of the EDZ (Excavation Damaged Zone) evolved in the granite. The measurements of borehole radar have given very good, while the measurements on the wall (radar, acoustic and tomography) have given good results. The GPR method has proven itself to be the most usable obtaining valuable information about the rock. Several typical differences can be observed that have been arisen on the sections of the two (base and repeated) measurements. These are appearing and strengthening of new reflections and diffractions. New processing techniques were developed for examination of amplitude and phase changes of different wave types on the borehole radar sections. The physical changes of the surroundings of tunnel can be mapped by these results. These changes can be explained only by realignment of stress and enlargement of classical EDZ.