By Michael Munro, John Walker, Behnam Pirouz
Introduction:
ATC Williams consultants are fortunate because they can ground their designs on technical data produced by our innovative in-house laboratory.
To produce safe and appropriate designs, it is essential engineering consultants are capable of the following:
- reliably interpreting technical data
- trust the raw data is accurate
- have a well-founded understanding of how the data was obtained
To celebrate forty years in business, we explore the laboratory milestones of specialty testing that allows our technicians and consultants to be at the forefront of industry and research.
Milestone 1: We begin
Soon after founding MPA Williams in 1981, Paul Williams established a laboratory to support the consultancy services. In the early days, the laboratory’s primary function was to undertake specialty tests unique to tailings that commercial laboratories did not typically provide. In addition to specialty tailings testing, the laboratory offered standard geotechnical tests (i.e. AS1289), eliminating the need to outsource part of a testing program.
In the mid-’80s, the laboratory started non-profit operations in a small room adjoining the consultancy offices, located in the Melbourne suburb of Bonbeach. The laboratory supported the needs of a small, yet dedicated, team of tailings consultants.
Milestone 2: The first tests – Rowe cells and soil dispersion
Notable exclusive in-house tests offered during the early years included large-diameter Rowe cell testing employed to assess large-strain consolidation of tailings. Commercially available Rowe cells are commonly small-diameter and manufactured from aluminium alloy prone to corrosion. Our technicians manufactured large-diameter pneumatic Rowe cells from stainless steel to ensure longevity, reduce edge effects, and permit long-duration testing of corrosive tailings. Read more here.
From the beginning, the laboratory technicians were proficient in carrying out typical soil classification tests, such as determination of particle size distribution, particle density, density determination, permeability, and Atterberg limits.
Over the years, advancements in testing methods resulted in the adaptation of some methods, such as introducing the vibrating table method for maximum density testing and the replacement of the Casagrande apparatus with the cone penetrometer for the determination of the liquid limit.
Soil dispersion has always been of great importance to our consultants. Early on, the technicians became proficient in undertaking Emerson and pinhole tests, which are simple and relatively inexpensive qualitative and quantitative test methods, respectively, used to investigate the dispersion potential of a soil. Read more here.
Milestone 3: NATA accreditation and advanced tailings testing
A significant development occurred in 1992 when the laboratory was granted NATA accreditation. The laboratory has continued to expand the scope of accreditation over the subsequent years, including ISO/IEC 17025.
The services offered by the laboratory has expanded significantly since the early days at Bonbeach to include other advanced tests such as shrinkage limit density, settled density, segregation threshold, triaxial, soil moisture characterisation, and rheology. Read more here.
Milestone 4: Relocation and cyclie triaxial testing
The relocation of the laboratory in 2006 to a larger facility in the Melbourne suburb of Mordialloc allowed for large-scale testing and additional equipment to expand test capabilities.
In 2016, the laboratory acquired the first cyclic triaxial apparatus allowing the stress-strain response and dynamic behaviour of soil and tailings to be determined for use in geotechnical designs. Currently, the laboratory offers advanced triaxial testing, including the determination of cyclic resistance to liquefaction based on the critical state theory, corrosive testing, custom stress paths, and more. Read more here.
Around the same time, ATC Williams increasing involvement in the design of capping/cover systems for rehabilitation design necessitated the purchase of soil moisture characterisation equipment (i.e. tensiometers, Tempe cells, etc.). This equipment allows technicians to determine the curve describing the amount of water retained in an unsaturated soil under equilibrium at a given matric potential. This is important for evaporation, and unsaturated seepage (vadose) modelling as it directly relates to the unsaturated hydraulic conductivity of soils.
Milestone 4: Rheology and pipe loop testing
In addition to geotechnical parameters, the slurry flow characteristics influence the design of tailings management systems. The tailings beach slope, head loss, pumping capacity, gradient in open channel flow, deposition velocity, and minimum transport velocity are essential design parameters.
The rheological test capabilities currently consist of rotary rheometry and pipe loop testing. Since 2000, the laboratory is equipped to perform bob and cup rotary rheometry. The test measures the rheological properties of non-Newtonian slurries for the prediction of beach slopes or the design of tailings transport systems.
The pipe loop facility is a modified arrangement of a capillary rheometer and is used to obtain flow characteristics of non-Newtonian and settling materials. The pipe loop consists of three pipes with varying diameters. Each pipe is fitted with pressure transducers to record the pressure drop along the pipes. Read more here.
The pipe blockage and re-suspendability test apparatus was recently added to the laboratories test capabilities. The apparatus evaluates the pipeline condition at shutdown and confirms the re-suspendability of deposited solids in the pipelines after shutdown. The test also provides an estimate of the duration the pipeline can be left full of tailings without flushing and if the pumping system can provide the required pressure to flush the pipe at startup.
The above testing capabilities assist ATC Williams Slurry Transport and Mechanical Engineering Group to optimise the designs for each project based on the unique tailings slurry properties and tailor-make an appropriate solution.
Milestone 5: TML testing
In 2011, the capabilities of the laboratory expanded to include Transportable Moisture Limit (TML) testing to service both the mining and maritime industries.
The iron ore industry approached ATC Williams due to several bulk carriers recently running into trouble while transporting iron ore fines by sea and the International Maritime Organization (IMO) reclassified iron ore fines as a potentially liquefiable cargo, meaning it had to undergo TML testing. Together with several overseas laboratories, ATC Williams was involved in the development of the Modified Proctor/Fagerberg TML test for iron ore fines.
In 2013, the laboratory was granted NATA accreditation for the determination of TML by the flow table method and several Proctor/Fagerberg methods. Read more here.
Milestone 6: In-situ testing
In-situ testing is another well-utilised service. Recovery of disturbed or undisturbed samples, in-situ density and shear strength are commonly performed, as are shear vane and dynamic cone penetrometer (DCP) tests. Recently, the laboratory acquired a PANDA probe (as a form of DCP) to determine the strength characteristics of in-situ soil or tailings.
Milestone 7: Future expansion
Although it is envisaged that the laboratory will remain focused on providing specialty services to the engineering consultants at ATC Williams, future expansion in terms of test capabilities, proficiency, and throughput is intended as the company continues to innovate and grow.
John Walker, Laboratory Manager, johnwa@atcwilliams.com.au 03 9590 9222
