5201

Describe and illustrate the geotechnical classification method developed by Brady and Brown (1993)
for different underground mining methods – ranging from “naturally supported” at one extreme, to
“unsupported” at the other extreme. (4 Marks)
(b) What is meant by “naturally supported” and “unsupported”, and what are the characteristics of each
of these categories in terms of orebody and near-field rock types, and stress states in the rock? (4
Marks)
(c) Illustrate this classification diagram by listing a number of representative mining methods (at least
two for each category) and explain why they are classified in this way. (4 Marks)
(d) What are some of the major core geotechnical risks associated with mining Document Preview:

Question 1 (20 marks) (a) Describe and illustrate the geotechnical classification method developed by Brady and Brown (1993) for different underground mining methods – ranging from “naturally supported” at one extreme, to “unsupported” at the other extreme. (4 Marks) (b) What is meant by “naturally supported” and “unsupported”, and what are the characteristics of each of these categories in terms of orebody and near-field rock types, and stress states in the rock? (4 Marks) (c) Illustrate this classification diagram by listing a number of representative mining methods (at least two for each category) and explain why they are classified in this way. (4 Marks) (d) What are some of the major core geotechnical risks associated with mining methods listed in (c) above, at these two extreme ends of this classification system? (8 Marks) 2Question 2 (20 marks) (a) A generic diagram of a slope in a jointed rock mass that is threatened by a planar slide is shown in the sketch. The critical joint that will control the slide has a cohesive strength of 69 kPa and a friction angle of 28°. The slope is located in moderate earthquake region and it is estimated that seismic coefficient (g) of 0.15 is sufficient to account for potential earthquakes. Based on information provided in Appendix 1: (i) Compute the safety factor of slope according to the information provided in the figure below. (6 Marks) (ii) Will drainage make the slope stable? (2 Marks) (iii) How much should the slope angle be decreased to stabilize it in drained condition to achieve a safety factor of unity? (4 Marks) 10 mWater table156 m123.32 m32?45? (b) With the exception of drainage and flattening state any two strategies you may use to stabilize the slope. (2 Marks) (c) State 6 sources of costs associated with slope failures in an open pit mine. (6 Marks) 3Question 3 (20 marks) (a) Explain the: (i) aims for geotechnical engineering…

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