9
As the grout pipe is assembled and pushed into the borehole, the piezometer assemblies
are added, and the electrical cables are fed into the borehole. When the grout tube has
reached its final position and the assembly is complete, a special weight (provided with
the equipment,) is tied to a length of aircraft cable and allowed to fall freely down the
inside of the grout pipe. As the weight hits each of the zip ties stretching across the pipe,
the zip tie is snapped, allowing the leaf springs to expand and force the filter stones
against the walls of the borehole.
3.2.2 Pneumatic Cutter Method
4500MLP sensors are designed to be installed around
flush coupled, one inch, Schd 80
PVC
grout pipe; however, other grouting arrangements may be used.
The assembly is held in its closed position during installation by two nylon zip ties
(supplied). Making sure the grout pipe is between the platens, and the cables from the
lower piezometers are kept
inside
the zip tie and leaf springs, attach the body of the
piezometer to the grout pipe by passing the zip ties through the eyebolts in the platens
and through the holes in the cutting tool. Orient the tool in such a way that it will be
above the assembly when pushed into the borehole. See Figure 11
.
Figure 11 - 4500MLP Pre-release
If the grout pipe is going to be removed from the borehole the grout pipe is assembled
and pushed into the borehole first, then each piezometer assembly is pushed around the
grout pipe (and any lower piezometer cables) to the desired elevation. Piezometers should
be installed sequentially, from the base of the borehole to the mouth.
If the grout pipe is to be left in place, the piezometers can be taped to the grout pipe.
(Make sure not to put the tape around the outside of the filter stone and spring
mechanism.)
