S4 to full-scale test correlation: new insights from an ‘open source’ RCP model


Papers # 2010 Vancouver

There is renewed interest in the correlation between critical pressures from lab-scale (S4) and full-scale RCP tests. The standard, supposedly material-independent correlation factor does provide a lower bound for data from many PE grades, but for some grades it is overconservative and for PA12 its applicability has been questioned. To investigate this issue and others, we return to the fracture mechanics modelling of both tests. Previous models have tended to be oversimplified, overcomplicated and/or computationally opaque. We present a flexible, analytically basic model which accounts for all major influences, including residual stress in the pipe wall and constraint from the surrounding backfill, using only a one-dimensional finite-difference method. Its results agree well with those from the earlier computational methods, while providing new insights on the role of processed-in residual stress, and of backfill under installed conditions.

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