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boundary, the task of finding the mesh which gives the most accurate result is simplified.
In the FEM the result will depend on the approximation of the displacements inside the
elastic space as well, so refinement has to be made in two directions. For a comparable
discretisation on the boundary, however, we find that the BEM gives the better answer
for this problem.
Figure 10.15
Distribution of vertical stress
10.5
SPHERICAL EXCAVATION
All problems analysed so far were two-dimensional. In order to show how more drastic
savings can be made when using the BEM we show an example in 3-D.
10.5.1
Problem statement
The example is similar to the example of a circular excavation in an infinite domain
except that the excavation is now spherical and the virgin stress is given by
00 ,0000
T
(10.8)
>
@
V
0
10.5.2
Boundary element discretisation and input
Two fairly coarse discretisations are used. Both meshes consist of only 3 boundary
elements, one consists of linear the other of parabolic elements. Three planes of
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