Page 196 - Buried Pipe Design

170 Chapter Three

standard Proctor maximum dry density. The curves for Pipe A are
measured results and Pipe B are predicted by the finite element
model. Physical pipe data and test results are as follows:

Curve
Parameter A B

Stiffness, lb/in 2 10 10
Thickness, in 0.285 0.300
Surface pressure, lb/in 2 48.9 50.0
Vertical deflection, percent 5.53 4.82
Horizontal deflection, percent 3.74 2.52

Figure 3.50 shows the load-deflection curve, and Fig. 3.51 shows
pipe strain versus position on the pipe for a surcharge pressure of
2
48.9 lb/in . Features of these results to note are the shape of the load-
deflection curve, relative magnitudes between the horizontal and ver-
tical ring deflections, and shape and magnitudes of bending and thrust
strain. This condition was modeled with FEA in several ways. These
illustrations also show the results from the FEA for a homogeneous
90 percent relative compaction with no compaction simulation. There
is a marked similarity between the FEA and test data. The pipe-strain
plot in Fig. 3.51 indicates that the magnitudes of pipe strain at a sur-
face pressure of 50.0 lb/in are fairly comparable. The ring deflections
2
determined from experiment and for FEA also compare quite closely.
Figures 3.52 and 3.53 show the results of the FEA for the homoge-
neous dense condition including compaction simulation during con-
struction. The physical pipe data and test results are as follows:

Curve
Parameter A B
Stiffness, lb/in 2 10 10
Thickness, in 0.285 0.300
Surface pressure, lb/in 2 48.9 50.0
Vertical deflection, percent 5.53 5.42
Horizontal deflection, percent 3.74 3.14

The compaction simulation load-deflection curve in Fig. 3.52 lost some
of the initial steepness compared with Fig. 3.50. However, the differ-
ence between vertical and horizontal deflection is maintained.
Deflections of Fig. 3.52 are similar in magnitude to those of Fig. 3.50.
Figure 3.53 shows pipe-strain plots for compaction simulation and a
surface pressure of 50.0 lb/in . Although the predicted pipe defections
2
were not improved by compaction simulation, a comparison of data in