When constructing a tunnel or a shaft in a fractured rock mass, the main water-bearing features are of major importance. A limited reduction in leakage, as well as a greater impact area, are potential consequences if these features are not considered in hydrogeological descriptions and in grouting design. This paper presents a grouting field experiment performed in a shallow, crystalline rock mass. An experiment where the spatial distribution of hydraulic conductivity (transmissivity) of water-bearing features was expected to show both directional dependence and connectivity. This was confirmed, grouting was performed, and hydraulic conductivity reduced. We expect that the demonstrated experimental work, highlighting general nature, pattern, and properties, can be used to improve hydrogeological descriptions and grouting design and form a basis for environmental impact assessments. Further, storage coefficient, and hydraulic aperture, based on transmissivity, can, potentially, be an additional indicator of fracture stiffness and situation of stress.
General nature, e.g., stratigraphy of soil or features in rock, the resulting geometrical pattern, and hydraulic properties, are key for grouting design and environmental impact assessments. Impact areas, with changes in head, may, for example, result in settlement of soil and damage to constructions. Since the same type of data can be used both for grouting design and as a basis for environmental impact assessments, more attention should be given to this double value of hydrogeological descriptions and the related data.
This paper presents a grouting field experiment performed in a shallow, crystalline rock mass within the Varberg tunnel project. The Varberg tunnel project includes the construction of a double track railway where the main tunnel and a service tunnel are built in rock and open troughs intersect both soil and rock. Focus for the field experiment were engineering feasibility and hydraulic efficiency, investigating spatial distribution of hydraulic conductivity (transmissivity) of main water-bearing features. Key aspects to address were connectivity, anisotropy, and heterogeneity.
