On the Use of Engineering Geological Information in Rock Grouting Design

Licentiate thesis, 2013

Underground rock construction is dependent on appropriate assessments of the geological settings at the project site. Relevant geological information must be collected, interpreted and communicated clearly with the aid of engineering geological prognoses. The general quality of the geological prognoses can be improved if the information relates to the engineering application and the project requirements. The work presented in this thesis aims to clarify ways in which this can be taken into account in grouting design throughout the construction process. Attention has been given to geological information that can increase understanding of the hydraulic properties of the rock mass. This was done by compiling relevant geological parameters and introducing hydraulic domains to define the various expected forms of hydraulic behaviour at a project site. A fracture transmissivity distribution model was presented for evaluating the sealing efficiency of grouting measures. The distribution model was also found useful for identifying differing flow configurations in the rock mass and indicating limitations in analytical models, which could be valuable for grouting design and inflow predictions. A study was also made of the current use of geological information in grouting design in Swedish tunnel projects. The study indicated that pre-defined grouting design classes are generally adapted to differing requirements but are less clearly modified in order to suit the variation in geological settings. Hydraulic domains are suggested to be used together with stated requirements to establish grouting classes adapted to both favourable and unfavourable scenarios, which is in accordance with the observational method. It is suggested that engineering geological prognoses based on hydraulic domains are made in the early phases of a project to facilitate identification of grouting design prerequisites and reduce the risk of encountering unforeseen ground conditions in later phases.