Stereonets

Question 1

How do you find the angle between two poles?

Answer 1

1. Rotate the plot until both poles
   lie on a common great circle.
   2 . Count the divisions between these poles along this great circle to compute the angle.
   This also gives the angle between the planes
   represented by these poles.

Question 2

Resultant force and Sliding Plane

Answer 2

We may then assume that the block will tend to move in the direction of r move in the direction of r , unless prevented’, unless prevented from doing so by the adjacent rock mass to the block.
The above constraint exists, if one or more of these discontinuity planes is oriented such that they are maintained in a state of compression by r . In such a case, the block can only fail by ’. In such a case, the block can only fail by sliding along the surface associated with the largest shear stress. The block surface line that makes the smallest angle with r that makes the smallest angle with r gives this ’ gives this potential sliding direction.

Question 3

Face area

Answer 3

A(f) = 1/2.l(a).l(b).sinθ(ab)

Question 4

Height of the apex

Answer 4

h = l(ab.)β(ab)

Question 5

Volume of the block

Answer 5

V = A(f).h/3

Question 6

Weight of the block

Answer 6

W = γ.V

Question 7

Methods of Support

Answer 7

• Rock dowels bolts & anchors
• Forepoling & roof pipe umbrella
• Shotcrete
• Steel ribs
• Segmental lining
• In situ concrete lining