Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology. / Pulsed Ultrasound Velocimetry combined with Pressure Difference (PUV+PD) measurement is a non-invasive in-line rheometric technique which is used to analyse the complex flow properties of industrial fluids for quality control purposes. Cape Peninsula University of Technology (CPUT) and Technical Research Institute of Sweden (SP) have developed and patented a new PUV+PD based system, called Flow-Viz™. Despite this advancement, the system and ultrasound sensor technology have not been fully tested and evaluated in a wide range of industrial fluids. Acoustic characterisation tests were carried out at SP, with the aim of understanding the ultrasound beam properties after propagating through industrial stainless steel (316L) pipe walls. For these tests, a high-precision robotic XYZ-scanner and needle hydrophone setup were used. Different ultrasound sensor configurations were mounted to a stainless steel pipe while using different coupling media between the transducer-to-wedge and sensor wedge-to-pipe boundaries. The ultrasound beam propagation after the wall interface was measured by navigating the needle hydrophone within a predefined 2-dimensional spatial grid. The most suitable coupling material was determined from the acoustic characterisation, and then used in the in-line rheological characterisation tests to evaluate the performance of the Flow-VizTM rheometric unit against conventional tube viscometry. The in-line rheological tests were conducted with bentonite, kaolin and Carboxymethyl cellulose (CMC) model fluids. The flow loop used consisted of three different pipe test sections; and two concentrations of each fluid were tested in order to ascertain the consistency of the measurements. The in-line rheological tests showed good agreement (±15%) between the two techniques and Flow-VizTM was able to provide important data at very low shear rates. Acoustic characterisation indicated that variations in the beam properties were highly dependent on the acoustic couplants used to mount the sensors to the stainless steel pipes. Furthermore, the in-line results showed the effectiveness of Flow-VizTM as an industrial rheometer. The non-invasive ultrasound sensor technology, was for the first time acoustically characterised through stainless steel. This information will now be used to further optimise the unique technology for advanced industrial applications, e.g. oil drilling fields, complex cement grout and food processing applications.

Grouting is performed in order to decrease the permeability and increase the stiffness of the material, especially soil and rock. For tunnelling and underground constructions, permeation grouting is done where cement based materials are pumped inside drilled boreholes under a constant pressure, higher than the ground water pressure. The aim of permeation grouting is to reduce the water flow into tunnels and caverns and to limit the lowering of the surrounding groundwater table. Cement based materials are commonly used as grout due to their availability and lower costs. To obtain a proper water sealing and reduce the lowering of the ground water table, a desired spread of grout must be achieved and the rheology of the cement grout is the governing factor for estimating the required spread. Rheological properties of cement grout such as viscosity and yield stress are commonly measured off-line using laboratory instruments, and some simple tools are available to make field measurements. Although the rheological properties of the grout that is used play a fundamental role in design and execution, no method has yet been developed to measure these properties in-line in field work. In addition to the real time measurement, there is no standard method for determining the yield stress for grouting applications. Despite the common usage of Bingham model fitting to determine the yield stress, the range of shear rate is often not specified or is neglected.   In this work, an in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements, known as “UVP+PD”, was successfully tested for continuous in-line measurements of concentrated micro cement based grouts. A major obstacle of using the ultrasound based methodology was the transducers, which would be capable of emitting sufficient acoustic energy and can be used in field conditions. The transducer technology was developed in a parallel project and the Flow-Viz industrial rheometer was found to be capable of detail measurement of the velocity profiles of cement grout. The shape of the velocity profiles was visualized, and the change in the shape of the profiles with concentration and time was observed. The viscosity and yield stress of the grout were determined using rheological models, e.g. Bingham and Herschel-Bulkley. In addition, rheological properties were determined using the non-model approach (gradient method) and the tube viscometry concept and were compared with results obtained using the rheological models. The UVP+PD method was found to be capable of determining the rheological behavior of cement grout regardless of the rheological model. The yield stress of cement grout was investigated using off-line rheometry techniques and UVP+PD in-line measurements. Tests were performed applying different shear histories and it was found that two ranges of yield stress indeed exist. Therefore, the design value of yield stress should be chosen with respect to the prevailing shear rate at the grout front for the required spread of grout. In addition, an appropriate shear rate range should be used when a Bingham fitting is done to determine the yield stress. In order to estimate the shear rate, plug thickness and velocity for one dimensional and two dimensional geometry, a non- dimensional nomogram was developed. The advantage of using the nomogram is that it does not depend on the applied pressure and the rheological properties of the grout and can therefore, be used as a simple design tool. Analytical approaches were used for the estimation and good agreements were found with numerical calculations and experimental results. In conclusion, in this work, it was found that it is possible to continuously measure the velocity profiles and determine the change of the rheological properties of cement grout using the ultrasound based UVP+PD method under field conditions. The yield stress was also investigated and it was found that two range of yield stress exist depending on the prevailing shear rate of the grout, which should be used for designing the grouting time at different conditions. In order to decide the design value of yield stress for grouting applications, a non-dimensional nomogram was developed that can be used to estimate the plug thickness, shear rate and velocity of the grout. / <p>Funding for the project was provided by the Swedish Rock Engineering Research Foundation (BeFo), The Swedish Research Council (FORMAS) and The Development Fund of the Swedish Construction Industry (SBUF), who are gratefully acknowledged. QC 20151112</p>