column of grout. Grouting was considered complete when the injection rate
for the 3:1 grout dropped below 0.1 cfm for a 5-min period. This rate was
determined by measuring the amount of grout in the sump tank at the begin-
ning and end of the period.
6.
The last tank reading shows that 10.6 cu ft of grout was left in the tank
when the hole was finished, and the first tank reading indicated that 1.5 cu ft
of grout was in the lines and pump. These two quantities together make
12.1 cu ft of 3:1 leftover grout. Since 12.1 cu ft of 3:1 grout contains approx-
imately 3.5 sacks of cement, that number of sacks must be subtracted from
the total number mixed for this hole to obtain the number of sacks (cubic
feet) of cement actually in the hole. The 12.1 cu ft is carried forward to the
next hole and would be a first entry in the log of the new hole if started with
3:1 grout. If the new hole should be started with 4:1 grout, 3.5 cu ft of water
would be added to the leftover grout to make 15.6 cu ft of 4:1 grout.
7.
A review of the pressures and injection rates recorded in the sample log
reveals no sudden changes or abnormalities. The log contains no evidence of
lifting or leakage. Minor fluctuations of rate would appear if the entries
were not rounded off. to the nearest 0.05 cu ft. The fluctuations are most of-
ten caused by recording time to the nearest half minute only. The increase
of pressure by increments permits direct observation of the effect of each
p r e s s u r e change. This is particularly important in stage grouting because it
is the practice to apply pressures to surface rock that in other situations
could only be used for rock under heavy confining loads. If the grouting
pressure in the sample log had been raised from O to 30 psi as fast as pos-
sible, the inspector, without visible evidence of lifting such as heaved rock
or surface breakouts, would not have any way to be certain that lifting was
not taking place.
8.
If an additional column is needed on this log form to record quantities of
filler or admixture in the grout, it can be provided by moving columns begin-
ning with ``Grout,, Cu Ft" to the right into the "Remarks" space. A second
additional column can be made available by recording the ` `Tank Reading"
data under "Remarks. "
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