Interpretation of Viscometer Test Results for Polymer Support Fluids

Polymer support fluids have been successfully used for the construction of bored piles (drilled shafts) and diaphragm walls for many years and yet, there is currently little guidance on the interpretation of their rheological properties from viscometer test results. In particular, there is confusion about the choice of an appropriate rheological model for this type of fluid. The use of oilfield units by some has also added to the confusion. To promote the use of SI units, this paper summarizes conversion factors that can be used to present viscometer data in a more uniform manner. Simple rheological concepts and instrument-specific equations are also given for those unfamiliar with the issues. Viscometer test results for two polymer fluids are then used to illustrate the application of the power-law model over the shear-rate range achievable with a typical direct-indicating viscometer.