11. The rock mass classification system that considers 'active stress' factor is
12. The rock specimen obtained from the overlying strata in a coal mine were tested in uni-axial compression and the following results were obtained at 50% of average compressive strength
Longitudinal strain = 0.06 and Lateral strain = 0.012
The ratio of vertical to horizontal stress in the mine is
Longitudinal strain = 0.06 and Lateral strain = 0.012
The ratio of vertical to horizontal stress in the mine is
13. A rock specimen of average thickness 0.8 cm failed at an applied load of 1000 kg during determination of shear strength by the punch test. The diameter of the punch is 2.8 cm, The shear strength of the rock specimen in kg/ cm2 is
14. Rock mass parameters for a shale rock, mb, s, and a of the Hoek and Brown failure criterion as given in the equation are 2.4, 0.01 and 0.52 respectively. The uni-axial compressive strength (σCi) of intact sh!le is 50 MPa.
$${\sigma _1} = {\sigma _3} + {\sigma _{ci}}{\left( {{m_b}\frac{{{\sigma _3}}}{{{\sigma _{ci}}}} + S} \right)^a}$$
The global rock mass strength of shale in MPa is
$${\sigma _1} = {\sigma _3} + {\sigma _{ci}}{\left( {{m_b}\frac{{{\sigma _3}}}{{{\sigma _{ci}}}} + S} \right)^a}$$
The global rock mass strength of shale in MPa is
15. Below mentioned are some features or cases of roof bolting. Identify one of such case where use of roof bolting may be ineffective?
16. From the stress-strain diagram shown below, the tangent and the secant moduli of elasticity in GPa are
