Geoscience Reference
In-Depth Information
Fig. 17.18. Overhead view of thelarge-scale ground rupturetest onthe
400-mm-diameter HDPE pipeline
extensometer probes external to the pipe and lasers to measure successive chord lengths
inside thepipeline.
The maximum axial strain measured was 8%, and the maximum circumferential strain
measured was 6%. The end reactions were 520kN. Figure 17.19 shows the axial strains
measured directly along the east springline of the pipe for 0.3, 0.6, 0.9, and 1.2m dis-
placements. Figure 17.20 shows the strain along both the east and west springline at the
maximum displacement of 1.2m. As can be seen in the figure, the axial strains were
symmetrically distributed withrespect totheground rupture location.
Figures 17.21 and 17.22 show the results of pre- and post-test laser profiling. A special
roboticcrawler,designedtoinspectpipelinesbyULCRobotics,DeerPark,NY,wasused
totransportavideocameraandlaserprofilingdevicethroughthepipelinebeforeandafter
thetest.Thelasergeneratesanimageofthepipecross-sectioncontinuouslyasthecrawler
traverses the pipeline. The image is stored digitally, and provides a measurement of the
shape. By subtracting the pre- and post-test images at the same location, the change in
shape, or cross-sectional deformation, is determined. Figures 17.21 and 17.22 show pre-
andpost-testframestakenat1msouthandnorthofthegroundrupture,respectively.The
racking and ovaling of the pipe isclearlyevident at each location.
The laser profiling measurements showed maximum ovaling, or increase in pipe diame-
ter, of 12% at the location of the ground rupture. The measurements also showed about
6% maximum loss of the internal cross-sectional area of the pipe. Most importantly,
the laser profiling provided an accurate, continuous record of cross-sectional change in
