The importance of seismic methods application for geological reconstruction of rockslide threatened open pit

Abstract

The significance of otherwise not frequently applied seismic methods in area of open pits increases by occurrence of unpredictable phenomena threatening the deposit during mining operation. Recognizing natural hazards as rockslide, its arrangement and examination of its formation may prevent the otherwise negative impact on economy of the mining and the mining safety. In this paper synthetic methodological approach including application of seismic refraction, seismic tomography, ground vibration monitoring and geological documentation in dolomite open pit Kraľovany-Rieka (Western Carpathians, Slovakia), where large rockslide covering area of 96,952 m2(Šimeková etal., 2013) evolved, is presented. Four 138 m long profiles were measured using Terraloc Mk8 24 channel seismograph with 10 Hz vertical geophones and geophone offset 6 m and processed by ReflexW Sandmeier scientific software. Seismic velocities and frequencies were during two blasts measured by three-channelled seismographs -UVS 1504, Vibraloc and VMS 2000 MP seismograph at four fixed standpoints to derive the ground transmission coefficient K, referring about the changes of the physical characteristics of the rock environment (Bongiovanni etal., 1991). Geological documentation included mapping and description of the basic lithological units. Results of the methods were integrated into the final model constructed by the Petrel modeling software. The case study revealed complicated geological-structural composition of the area with basement from granodiorites passing upward into thick-bedded carbonates, which are locally covered by Quaternary deposits. Primary factor influencing the rockslide triggering by steep inclination of the basement and faults formation is tectonics. Dense spatial distribution of two fault systems caused a segmentation of the carbonates into several, independently moving blocks. Further agents weakening the rock mass stability were climatic conditions and additional mining activity contributing to gravity driven independent movement of blocks. Seismic refraction and seismic tomography proved as valuable method for geological and structural reconstructions of the open pit and rockslide that are necessary preconditions for the rockslide movement prediction and suggestions of the effective landslide control.