APPROACHING REFUSAL

Eventually, as the grouting of the hole proceeds, either the take slows down and approaches refusal or else refusal is unlikely to be reached because the take will obviously continue indefinitely if permitted to do so. Of course the use of special treatment to deal with problems may also result in refusal not being reached.

WHEN REFUSAL IS APPROACHING

Grouting should be continued until virtually no grout is taken in a 15-minute (or similar) measuring interval.

RUNAWAY AND EXCESSIVE TAKES

Large, long cracks can produce these takes. It is not good practice to keep supplying grout to a hole with a large take continuing indefinitely. In most cases the grout is penetrating too far and is partly wasted, particularly if a curtain is being constructed: the aim is to grout the vicinity of the curtain, not far and wide away from it.

Recommended practice is to stop grouting when a fairly substantial amount of cement has been injected and then to let this set before resuming 24 hours later.

If this second application continues the fast-taking behaviour, it should be given the same treatment. Several more applications may be necessary before getting refusal.