When tunnels are excavated by drill and blast there are several processes that generates forces/tensions on the grout, such as vibrations, blast induced forces, water flow etc. Extensive laboratory work was conducted to find crucial parameters on grout to assess a fundamental understanding on how a grout can be characterized to cope with future demands on grout. The work comprised of advanced laboratory testing on cement compared more traditional testing. 

The shear modulus is measured in this study for cement grout over five hours of hardening time. It is shown that grout with lower w/c hardens faster i.e., more rapid growth of shear modulus. Cement grout has a relatively high shear modulus which increases over time, where the viscous and elastic shear moduli intersect at a point which is believed to correlate to a change in failure mechanism Rheological tests are performed to study the first five hours of the hardening process of the grout. The setup was with oscillating concentric cylinder, with both constant amplitude and frequency. The shear moduli over time can be computed, which in this case can be seen as a first attempt to describe a shear moduli of cement grout. This could help to describe the characteristics of a grout, to understand the forces that the grout encounters during a full drill-and blast cycle.

Vid tunnelbrytning finns flera processer som kan påverka injekteringsbruk. Tidigare studier har genomförts för att karakterisera injekteringsbruk genom att mäta tillväxten av skjuvmoduler över tid. Skjuvmodulen är förhållandet mellan skjuvspänning och skjuvtöjning, och kan delas in i viskös skjuvmodul och elastisk skjuvmodul. Förhållandet mellan dessa två parametrar beskriver var materialet befinner sig på det viskoelastiska spektrumet. Injekteringsbruk är ett material som härdar över tid, vilket innebär att cementen förflyttas längs det viskoelastiska spektrumet. I denna studie mäts och jämförs skjuvmodulerna med varandra för fyra olika typer av injekteringsbruk under de första fem timmarna i härdningsprocessen. Från resultaten skapas en konceptuell betraktelse för hur skjuvmodulerna påverkar injekteringsresultaten. Genom att mäta skjuvmodulerna och relatera resultaten till vibrationer från sprängningar, hydraulisk gradient och vattenkraft från vattenförlustmätningar, kan skjuvmodulernas påverkan bestämmas. Mätningen av skjuvmodulerna utförs främst i en laboratoriemiljö. Baserat på de olika resultaten föreslås en rekommendation för implementering av skjuvmoduler vid design av injektering.

During tunnel excavation there are several processes which generates stress on grout. Previous studies have been conducted to characterize grout by measuring the growth of shear moduli over time. Shear modulus is the relation between shear stress and shear strain and can be divided into viscous shear modulus and elastic shear modulus. The relationship between these two parameters describes where the material is on the viscoelastic spectrum. Grout is a material that cures over time, which means it is constantly moving across the viscoelastic spectrum. In this study, the shear modulus is measured and compared between four different types of grouting material during the first five hours of curing. Based on the results, a conceptual model is then created to determine how the shear modulus affects the grouting results. By measuring the shear modulus and relating the results to blast induced vibrations and hydraulic gradient, the influence of shear modulus is determined. Measurements of shear modulus is conducted in a laboratory environment and based on the results of the study; an implementation of shear moduli is suggested to improve the design of grout.

When underground rock constructions are excavated, it is common practice to re-duce the water ingress into the tunnel by grouting. In hard rock, the water ingress mainly occurs in the open fractures inside the rock mass.When conducting a grouting design, it is important to have a proper understanding of the hy-drogeological conditions in the rock mass to correctly assess the hydraulic gradient which is act-ing on the grout. One phenomenon that occurs and damages the grout is viscous fingering. Vis-cous fingering occurs when a more viscous fluid is displacing a less viscous fluid, creating the appearance of “fingers” in the more viscous fluid. The viscous fingering will occur in the region where the pressure gradient of the grout is lower than the hydraulic gradient, resulting in a poor grout spread. Today, when a grout design is conducted, the penetration length is of high im-portance. However, the designed penetration length includes the region where viscous fingering occurs, which in turn results in an incorrect design or poor grout quality.To study this, a mathematical model is derived from the Navier Stokes equations to predict the region where viscous fingering occurs during grouting of cement. In conjunction with this math-ematical model, a common type of cement grout is characterized by conducting rheological meas-urements which are then implemented into the mathematical model.The results show that stable grouting can be achieved in the early stage of process and be me-chanically stable over a long term by properly predicting the region where viscous fingering oc-curs.