Static Penetration Test of Button Chip for Rock Drill Focused on Effect of Spacing

Seisuke OKUBO, Katsunori FUKUI and Akinori OTA

J. of MMIJ, Vol.115, No.9 ,pp.661-667 (1999)

A proper testing method to examine the effect of spacing on penetration depth has not been established up to now. In this study, a simple testing method was proposed in which a button chip was penetrated on flat surface of a sample rock, 25 times in five by five square pattern. When applied force was relatively small, solitary penetration holes on rock surface were made at pre-determined spacings or intervals. When higher force was applied, rock between holes was chipped away or broken completely and holes were connected each other to produce a large excavated region covering all testing area.

Through comprehensive testing schedule, followings were found;

1. Required force to penetrate a certain depth is proportional to square root of the chip diameter.

2. For Sanjome andesite and Kimachi sandstone, penetration depth approximately follows an equation with three constants 'a' , 'n' and 'c';
(depth) = a (force)/(chip diameter)0.5 - b(spacing)sn - c,
where 'n' takes a value between 1.5-2.0.

3. For Inada granite, penetration depth follows an equation;
(depth) = a (force)/{(chip diameter)0.5 (spacing)0.5} - c .

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