Rock Mechanics And Roof Supporting — Part 1 MCQs with Explanations

The load-bearing capacity (LBC) of a timber prop depends on its dimensions and the type of wood used. For a 2.5 m long timber prop with a diameter of 15 cm (which is approximately 0.15 m), the expected range of LBC typically falls within 50 to 60 kN (kiloNewtons). This assumes a standard load capacity for timber props used in mining and construction to support roofs or walls. Let's analyze each option: Option A: "5 - 10 kN" - This range is too low for a timber prop of this size and diameter. Option B: "15 - 20 kN" - This range is still too low for a timber prop of this size and diameter. Option C: "50 - 60 kN" - This range is within the expected load-bearing capacity for a timber prop of this size and diameter. Option D: "120 - 130 kN" - This range is too high for a timber prop of this size and diameter. Therefore, the correct answer is Option C: 50 - 60 kN .

layers thickness is the correct answer to “Which of the following is not considered in Bieniawski's geo-mechanics classification”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

point load test is the correct answer to “Which of the following test may be used to provide an indirect estimate of uniaxial compressive strength”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

1.25 is the correct answer to “A piece of coal sample weighs 10 kg in air and 2 kg when immersed in water. The specific gravity of the coal sample is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

14.55 is the correct answer to “A dry rock sample of diameter 50 mm and length 100 mm weighs 300 g. After saturating in brine solution of specific gravity 1.05, its weight increased to 330g. The porosity of the rock sample in percentage is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

30 MPa is the correct answer to “A core of 10 cm height and 5.4 cm diameter is subjected to diametrical point loading. The ram of the hydraulic jack has a cross sectional area of 12.5 cm 2 and the dial gauge reading is 3 MPa. What is the point load strength”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

11.1 is the correct answer to “The grain density and bulk density of a dry coarse gained sandstone rock sample are 3.0 gm/cc and 2.7 gm/cc respectively. The void ratio of the sample in percentage is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

all of the above is the correct answer to “Objectives of roof supporting in underground is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

50 cm is the correct answer to “During setting of supports in underground, a lid is used over the prop. The length of such lid shall not be less than”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Mohr's circle diagram is the correct answer to “Which of the following diagram can represent one aspect of bi-axial stress acting on a point with respect to a set of reference axes”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Q-system is the correct answer to “The rock mass classification system that considers 'active stress' factor is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

4.0 is the correct answer to “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”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

142.10 is the correct answer to “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/ cm 2 is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

10.29 is the correct answer to “Rock mass parameters for a shale rock, m b , 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 (σ Ci ) 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”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

application in highly watery face is the correct answer to “Below mentioned are some features or cases of roof bolting. Identify one of such case where use of roof bolting may be ineffective”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

4.0, 2.2 is the correct answer to “From the stress-strain diagram shown below, the tangent and the secant moduli of elasticity in GPa are”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Texture is the correct answer to “The grain size distribution of soil is known as”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

plug subsidence is the correct answer to “Chimney caving involves the progressive migration of an unsupported mining activity and the sudden mode of formation rather than progressive one is known as”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Rose diagram is the correct answer to “Name the diagram where the strikes of discontinuities are oriented at about 5° interval”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Gypsum, Calcite, Topaz, Diamond is the correct answer to “In the Mohr's scale of hardness, the minerals in increasing sequence of hardness are”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

recovery and re-use is the correct answer to “Identify from below the advantage of steel support over timber support”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

158.00 is the correct answer to “A core sample of 54 mm diameter having Young's modulus of 68.97 Gpa fails in uniaxial compression at 0.1% axial strain. The axial load at failure in kN is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

In-situ stress in rock is the correct answer to “The instrument Flat jack is used for measuring the”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

RMR = 9 loge Q + 44 is the correct answer to “Correlation between the rock mass classification systems of RMR and Q is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

wooden cog is the correct answer to “Chockmate is used in metal mines. Which of the following coal mine support is similar to chockmate”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Mining Sirdar is the correct answer to “As per DGMS Circular 7/2002, who out of the following shall be responsible to assess the requirements of support in underground”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

157.9 is the correct answer to “The uniaxial compressive strength of a limestone sample is 80 MPa. The sample is confined at a pressure of 20 MPa in a triaxial compressive strength test. Based on Hoek-Brown failure criteria the maximum principal stress at failure in MPa is (Consider rock constants as m = 7.88, s = 1.0 and a = 0.5)”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

0.28 is the correct answer to “A rock specimen of 120 mm length and 54 mm diameter is subjected to uniaxial compressive loading. Two strain gauges, one axially and other radially, are attached to the specimen. At the breaking load, if these two gauges read 0.0082 m/m and 0.0023 m/m respectively, the Poisson's ratio of the specimen is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

longwall mining is the correct answer to “Powered support is used in”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

1.5 bolt/m2 is the correct answer to “Which of the following bolting density has been prescribed for poor types of roof”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

differential method is the correct answer to “Computational methods of stress analysis fall into two distinct categories - one of them is intregral, what is the other”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

triaxial cell is the correct answer to “Which of the following cell is sometimes used to investigate the shear behaviour of discontinuities”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

40 is the correct answer to “For a typical hard rock with E = 10 5 Mpa and Poisson's ratio $$\left( \upsilon \right)$$ = 0.25, the modulus of rigidity in GPa is”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

It is the stress which governs the gross mechanical response of a porous material is the correct answer to “What do you mean by effective stress”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

full column grouted roof bolt is the correct answer to “In freshly exposed roof area of developing working, which of the following support should be preferably used”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

pit prop is the correct answer to “Which of the following may be called as quick setting support”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

54 × T is the correct answer to “What will be safe cover i.e. the tolerance limit for extraction of coal pillars with caving where railway line is on the surface? T is the seam thickness in meter”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

14.43, 30.0 is the correct answer to “A series of tri-axial compression tests conducted on sandstone samples reveal the following relationship between major and minor principal stresses σ 1 = 50 + 30σ 3 [stresses are in MPa) The cohesion in MPa and angle of internal friction in degrees of sandstone respectively are”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

122.6 kN is the correct answer to “A tension crack of 5 m depth behind a rock slope crest is completely filled with water. What is the horizontal force exerted on a unit slope length by the water in the tension crack”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.

Griffith is the correct answer to “"A crack will extend only when the total potential energy of the system of applied forces and material decreases or remain constant with an increase in crack length" - Who has given this concept”. This question is standard in competitive examination syllabi for Rock Mechanics And Roof Supporting.