APPENDIX II
S A M P L E GROUTING LOG
1.
In the grouting log (fig. II-1), the inspector has collected pertinent infor-
mation from the drilling and pressure testing records and knows that he is
going to grout zone 4 of a primary hole, that the hole is inclined 25 deg from
the vertical, that the top of the zone to be grouted is 68 ft vertically below
the surface, that the hole was pressure-tested at the rate of 0.5 cfm at 10 psi,
and that the top of zone 4 is below the water table. From figure 4 (main
text), he finds that pressures exerted by grout columns of 2:1 and 1:1 grout
1 ft high are 0.61 and 0.73, respectively. Grout columns of these mixes 68 ft
high would exert pressures of about 42 and 49 psi. This means that if 1:1
grout is used, the maximum gage pressure should be 19 psi so that the total
pressure at the top of zone 4 will not exceed 68 psi (1 psi per foot of verti-
cal depth).
2.
The inspector decides to start with 4:1 grout, although 3:1 grout would be
an acceptable starting mix considering the pressure-test results and the fact
that all of zone 4 is below the water table. After the header is in place with
the valve to the hole closed and the valve on the return line open and the con-
tractor is ready to begin grouting, the inspector asks for a three-sack batch
of 4:1 grout. This should be enough to find out if the hole will take grout. (A
two -sack batch would make little more than enough to cover the suction in-
take to the pump and fill the pump and grout lines. ) A three -sack batch of
4:1 grout will make 13.5 cu ft since a sack of cement (94 lb) has a volume of
only O.5 cu ft when immersed in water. The volume of each batch mixed is
entered under the heading ` `Grout, Cu Ft. " Note that the first entry in the
column headed " T a n k Reading" shows 12.0 cu ft of grout in the sump tank.
This reading is made after the grout has been circulated through the pump
and grout lines. The difference between 13.5 cu ft and 12.0 cu ft is the
amount of grout required to fill the pump and lines. After circulating the
grout and getting the tank reading, the inspector is ready to start grouting.
The valve to the hole is opened and the valve on the return line is closed as
required to divert grout into the hole at the pressure designated.
3.
Pressure can be obtained as desired without completely closing the re-
turn line. The inspector asks that it be held to 10 psi while he determines
the rate of injection. He does this by measuring the amount of grout in the
tank after 5 min of pumping with a stick gage calibrated to read in cubic feet
for that particular tank. He finds that 9.5 cu ft of grout remain in the tank. `
Thus, 2.5 cu ft of grout were pumped into the hole during the first 5 min of
grouting, which gives a rate of 0.5 cfm. Usually the rate of injection, shown
in the seventh column on the sample log, is computed on batch quantities,
assuming that the level of grout in the sump tank is the same each time a
new batch is discharged from the mixer. More frequent observations on the
73
Previous Page
