Abstract
To ensure successful sealing of rock and soil, an adequate description of the system to be grouted is required as a basis for the grouting design and the selection of the grouting material. In rock, the individual fractures and the hydraulic apertures of these fractures form the basis of the Swedish grouting design concept. The hydraulic aperture is a key parameter when describing grouting behaviour and it is used to determine the extent to which the grout can enter fractures – that is, the penetrability. The hydraulic aperture also determines the penetration length, and therefore the grout parameters (e.g. yield stress and viscosity) as well as the grouting pressure and time needed to be adopted to the hydraulic aperture. Once these parameters are chosen, a suitable grouting technique can be adopted. Simple, practical rock and grout tests are important inputs to ensure correct design and performance. The aim of this paper is to present a testing procedure and provide examples from laboratory and field experience to demonstrate that the approach also works in practice.
Highlights
Notation b hydraulic aperture bfilter gap in a PenetraCone where grout flow changes from continuous flow to dripping bstop gap in a PenetraCone where grout dripping ceases and the flow stops dhw difference in hydraulic head dpw difference in water pressure d95 grain size below which 95% of the grains fall g acceleration due to gravity dimensionless penetration length
Successful sealing of rock and soil requires an adequate description of the system to be grouted (e.g. Fransson, 2001a; Hernqvist et al, 2012; Kvartsberg, 2013) as a basis for the grouting design and the selection of the grouting material
Silica sol is modelled as a gelling Newtonian fluid that rheologically is only described by its viscosity development over time
Summary
Successful sealing of rock and soil requires an adequate description of the system to be grouted (e.g. Fransson, 2001a; Hernqvist et al, 2012; Kvartsberg, 2013) as a basis for the grouting design and the selection of the grouting material. Equations 1–6 and a graph (Figure 3) are used to estimate the penetration length for a cement-based grout (Bingham fluid). These equations are described in Gustafson and Stille (2005), which is based on the manuscript later presented by Gustafson et al (2013). Due to the high hydraulic head (320 m) and gradient, grouting design aimed at a stiff grout with a yield strength of 15 Pa. Using the data for the investigation borehole at Äspö HRL (Table 1), the following estimates of a maximum penetration length Imax and a characteristic time t0 were obtained. This can be estimated directly using equations behind the graph pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 4: ID % Θ2 þ 4Θ À Θ
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