Tafadzwa John Shamu

Rock grouting is a widely used construction method for sealing rock fractures, e.g. in underground tunnels for the subway system around Sweden, where good rock conditions exist. Cement-based grouts are the main injection materials for sealing and their rheological properties (viscosity, yield stress) largely contribute to the success of the grouting operation, i.e. achieving sufficient spread to seal fractures. From an environmental point of view, grouting is essential for controlling groundwater flow as well as reducing the risk of settlement to nearby buildings. Actually, in all underground projects in Sweden, there is an environmental court ruling that dictates the amount of water that is allowed into the excavated zones, and the cost to avoid water-related issues can be up to ~10% of the total project revenue.

As a Ph.D. student at the Division of Soil and Rock Mechanics at KTH, my research studies are focused on the rheological characterization of cement grouts that are used in different grouting applications. Generally, my work involves developing experimental test procedures and methods to measure grout rheology. The core of the research work is aimed at the implementation of an ultrasound-based system for measuring grout rheology in real-time for enhanced grouting performance. This research work would benefit the grouting industry with a measurement method that is digitized and allows rheological data logging for continuous real-time process improvement and reliable grouting records. The currently used methods are based on simple empirical devices that are unreliable, prone to human error and not able to be used in future automated grouting systems. Additionally, my work encompasses the design of experimental models that emulate in a simplified way the complex flows of cement suspensions in rock fractures to better understand them in order to improve grouting design and execution.