A COMPARATIVE STUDY FOR STRENGTH CLASSIFICATION
The importance of providing a system for strength classification is emphasized by the diversity of testing methods, number of representative samples needed, and testing equipment required. In the present work three Egyptian types of rocks: Limestone, Sandstone and Granite with different specimen sizes are used to carry out a comparative study concerning the determination of the compressive strength using uniaxial compression, point-load, and Schmidt hammer techniques. Testing results are statistically analyzed and correlated with some physical properties like porosity, density and sound velocity. * Associate Professor, Mining Department, Faculty of Engineering, Cario University TÜRKİYE X I I I . M A D E N C İ L İ K K O N G R E S İ , 1 9 9 3
Influence of blast delay time on rock fragmentation: One-tenth scale tests
ABSTRACT The Bureau of Mines 1s studying blast delay timing influences on rock fragmentation in a series of tests that started in 3-ft concrete blocks and includes reduced-scale and full-scale bench blasts. This paper reports on the reduced-scale tests. In a 45-in high dolomite bench, 18 single-row blasts were fired with 15-in burdens. Spacings were 21 and 30 in. Delay intervals ranged from 0 to 45 ms, equivalent to 0 to 36 ms/ft of burden. Each shot was instrumented for strain and pressure for both in situ dynamics and interactions between blastholes. All fragmented rock was screened. The finest fragmentation occurred at blasthole delay intervals of 1 to 17 ms/ft of burden. In this range, stress-wave-induced strains interacted with longer lasting gas-pressure strains from earlier holes. Coarse fragmentation resulted from short delays ( <1 ms/ft), where breakage approached presplit conditions with a major fracture between blastholes and large blocks in the burden region. Coarse fragmentation also resulted...
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.