Advanced topics - The Boundary Element Method with Programming - page 469

and this will be applied as initial stress.

V E H

H strain in direction of bolt

Modulus of rock
Modulus of bolt

xBolt Bolt x

x

E
E

Rock

Bolt

V E H

xRock Rock x

Cross-sectional area A

Figure 18.6 Explanation of difference in stress between rock bolt and rock mass

2

[

3

1

Figure 18.7 Linear cell element

To compute the strain along the rock bolt we use a line cell as shown in Fig. 18.7.
First we compute the displacements at the cell nodes using Eq. (9.48)

E N E N

¦

¦ ¦¦

e
n

e
n

e
n

e
n

u

P

' U t ' T u

(18.11)

e 1 n 1 e 1 n 1

where P is a cell node. We introduce a local coordinate system specified by vectors
s along the rock bolt and s perpendicular to it (Figure 18.8). The values of the