by Michael Munro, Associate Engineer
ATC William’s NATA accredited laboratory, based in Melbourne, routinely volunteers to participate in round robin (or proficiency) programs to understand how results from various ATC Williams laboratory tests directly compare against other laboratories.
The purpose of round robin testing
Laboratories that take part in these proficiency programs include commercial laboratories, other consultancies, and universities/colleges.
ATC Williams takes advantage of these programs to assess our competence and expertise to ensure our standards and procedures produce results that are on par with industry expectations.
Important lessons can be learned from undertaking these proficiency programs even if the results are comparable, and not outlying, from the other participants.
The challenge explained
A recent round robin testing program focused on the repeatability of, and variability of methods currently used for laboratory testing to assess consolidation properties of a slurry sample (including permeability).
This program was initiated by Dr David Reid from the University of Western Australia, and ultimately twenty-six laboratories submitted results. The results of the program will be presented and discussed in a peer-reviewed journal paper currently under preparation.
The participants were provided with a representative sample of fine-grained iron ore tailings and asked to give an expression describing the relationship between void ratio and vertical effective stress, and void ratio and hydraulic conductivity (i.e. permeability), covering a pressure range up to 500 kPa.
The selected method
There are several methods available to ascertain the aforementioned expressions. We opted to undertake one-dimensional Rowe Cell consolidation testing with direct measurement of hydraulic conductivity.
Our laboratory Rowe Cells are specifically manufactured for specialty tailings testing and have significantly larger diameters compared to standard Rowe Cells used for testing consolidation characteristics of soils.
In this case, the sample was poured at a self-levelling solids concentration into the cell and left to settle, prior to applying any load. The load is pneumatically applied to the sample via bellows located at the top of the cell.
We evaluated the sample at ten confining pressures ranging from 1.25 kPa to 640 kPa, with the hydraulic conductivity of the sample being directly measured after each stage of consolidation.
High quality results
The results from the test were plotted, and expressions were interpreted, for subsequent submission. Figure 1 and Figure 2 presents the data from the Rowe Cell test, and expressions submitted describing the relationships.
For this article, we compared the results against those from the University of Western Australia. The results from the other participants are presented alongside. The original data has also been made available on LinkedIn by Dr David Reid.
ATC Williams reports Rowe Cell consolidation results between 1 kPa & 1000 kPa, therefore, we considered only an expression within this range.
The data presented indicates the high quality and consistency of results produced by ATC William’s laboratory. Our consultants ground their designs on results produced from our laboratory. The results from participating in proficiency programs like these affords confidence that our designs are safe and appropriate.
Our laboratory offers the advantage of directly servicing our consultancy, and ensures the limitations and intended purpose of the test is understood, and the results are appropriately interpreted.
To enquire about the ATC Williams laboratory, please contact John Walker or Luke Renkin on (03) 9590 9222.