| Summary: | Grouting has been used in ground engineering since the early 19th century. Grouts are injected into the ground both for the creation of hydraulic barriers and for ensuring ground stability. Example applications are dam sealing, underground isolation of waste disposal sites, stabilisation of mine workings and prevention of water ingress during tunnelling. A key problem facing the grouting industry is that once the grout has been injected into the ground, it is impossible to detect where the grout material has gone. As a consequence, the integrity of the hydraulic barrier, or in the case of ground improvement the filling of all significant voids, cannot be guaranteed. This leads to huge conservatism in the industry, with large numbers of unnecessary injection boreholes being drilled. This Ph.D. thesis aims to create a detectable grout by the addition of magnetic materials to traditional cementitious grouts. Laboratory experiments have been undertaken to determine both the magnetic susceptibility and engineering properties of the detectable grout. These experiments have shown that, with the addition of magnetite, a viable detectable cementitious grout mixture can be produced. Samples of the detectable grout were then produced for use in two field trials. The first field trial provided the proof of concept that the grout could be detected both outside of the laboratory environment and at depth. The second field trial established how the magnetic field of the detectable grout changed with distance. The rate of decay of the magnetic field in all directions was established, with the grout being detected at a maximum distance of 3 m. This thesis has provided the first proof of concept that a magnetically susceptible cementitious grout, once injected into the subsurface, can be detected with a magnetometer. The data could then be used to determine the location and shape of the grouted rock volume. This detectable grouting system has the potential to reduce the inefficiencies and uncertainties currently present in the grouting industry.
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