SEISMIC WAVES VELOCITIES AS AN INDICATOR FOR ASSESSING EXCAVATABILITY OF SEDIMENTARY ROCKS

The selection of excavation technology is one of the very important and demanding tasks when planning excavation in solid rocks, whether on a surface mine or construction pit. The variety of rock mass characteristics greatly influences the application efficiency of a particular excavation technique and technology. The discontinuous rock mass is easier to excavate compared to solid rock mass. Discontinuity is a well-known characteristic of rock masses, especially sedimentary ones, and this feature is very successfully investigated using non-invasive, fast and relatively inexpensive seismic geophysical methods. The results of seismic investigations are the velocities of compression or primary P-waves and shear or secondary S-waves. Some of the methods from the literature use the mentioned seismic wave velocities as the primary indicator for assessing the possibility of rock excavation. This paper presents the application of several such methods on the example of rock mass categorization for excavation in the ferry port Žigljen on the island of Pag. During field measurements, geophysical methods of shallow refractive seismic (SRS) and multichannel analysis of surface waves (MASW) were used. Based on the measured seismic wave velocities, the rock mass at the investigation site was categorized as a non-mechanically excavated material according to all classification methods employed. Therefore, blasting with the use of blast holes and explosives is recommended for excavation.