An approach to evaluation of strength characteristics of rocks in boreholes

Conclusions

• 1. An approach to shock contact-strength (SCS) evaluation is proposed that allows, on the basis of the instrument package developed, fairly rapid measurement of the pertinent strength characteristics of rocks in borenhole and blasthole sections.

• 2. Laboratory and field test data have revealed a pronounced statistical link of the SCS data with several well-known parameters and features of the mechanical properties of rocks.

• 3. The proposed method can be employed most efficiently in those cases where core test data are not available at all or are available partially, in particular for assessing strength of rocks in blastholes as well as in engineering and geological drill holes when the yield of core suitable for mechanical tests is low. If there are appropriate grounds, the method may be applied for petrographic zonation of rocks and delineation of productive areas.

In view of the complicated mechanism of stress pulse generation at the SCS sensor output (dependence on the moduli of elasticity and deformation, piezoelectric transducer conversion function, design of the shock device, etc.), the functions of the relationship of SCS signals with specific features of the mechanical properties of rocks should be determined by the correlations analysis method. The stability of the mechanoelectrical conversion factor may be monitored with the help of samples specially prepared from homogeneous materials (concrete, duralumin, epoxy compounds, etc.).