State of the Art Report on Cement Based Grout Properties and Dynamic Grouting

Sammanfattning: Dynamic grouting in rock mass has been studied since 1985 while desired penetration in rock masses with fine fractures is still a challenge because of uncertainty and complexity in the grouting process. This has attracted the attention of researchers in different countries and regions, especially in some Nordic countries such as Sweden. This study presents a comprehensive review of grouting relevant research, including factors that influence penetration, different evaluation systems (equipment, and methods), and a variety of grouting techniques. Filtration as the main obstacle is a tendency that particles of suspensions would gradually separate from the flow and block the flow path. Hence, the effects of various factors on filtration are discussed in detail based on previous research and experiments. Factors such as temperature, grain size, and w/c ratio were found to have a dominant influence on filtration stability and rheology. This means rheology and filtration are highly coupled and brings more difficulties in penetration investigation with dynamic grouting. Therefore, the influence of each factor on rheology and filtration was discussed to help with the understanding of the mechanism in different grouting techniques. Then a review of dynamic grouting methods from 1985 is made in chronological order to find the limitations on existing equipment and evaluation methods. Even it is difficult to conclude the most efficient grouting method in micro-fractures without the quantitative comparison of efficiency, this review paves the way to a more systematic exploration of novel grouting equipment and techniques. Meanwhile, a contradiction regarding the influence of high-frequency oscillatory pressure on viscosity was revealed. Rather than rapid dissipation of pressure in the slots, the thermal effect caused by high-frequency oscillatory grouting is introduced to explain its adverse impact on penetration in fractures (250 and 100μm). The potential reason is the faster hydration of grouts resulted from the increased temperature and the speed of molecular motion. In the end, by evaluating the benefits from different combinations of grouting methods. It was found that the ultrasound dispersing method along with low-frequency rectangular pressure impulse would contribute to the rheology and filtration stability in the mixing and grouting phase respectively. With the application of CDF simulation, this proposal and the assumption of the thermal effect of high-frequency oscillatory pressure can be better verified in future research.