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3.2 Borehole Installation
In steeply inclined boreholes directed downwards, the drop weight method of installation is
recommended. See Section 3.2.1.
(Note that the drop weight method cannot be used in holes that will not stay open, and in holes
which require the casing to be removed as the piezometers are installed. This is because when
using the drop weight method the top piezometers are released first.)
For shallow inclinations and upward directed holes, (and for other situations where the drop
weight method is not desired or possible,) the pneumatic cutter method or the pull-pin method
can be used. See Sections 3.2.2 and 3.2.3.
3.2.1 The Drop Weight 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.
Preparing the grout pipe:
1)
Connect the sections of grout pipe together and lay them out along the ground.
2)
Mark the desired locations of the piezometers on the grout pipe at the calculated
depths.
3)
Drill a single 7/32 or 1/4 inch drill hole diametrically through the pipe in each marked
location.
Attaching the piezometers:
Each piezometer assembly is held to the grout pipe by means of a single 50 lb. nylon zip
tie (supplied), which passes through the two holes on opposite sides of the pipe. The zip
tie also holds the piezometer assembly in its closed position.
Pass the zip tie through the grout pipe, through the spaces between the leaf springs,
around the two platens, and then back to itself. Keep the cables from lower piezometers
inside
the zip tie and leaf springs. The zip tie should pass just
below
the center leaf
spring so that the bottom of the platen assemblies will be held tight to the grout pipe.
Pull the zip tie tight around the grout pipe (Figure 10).
Figure 10 - 4500MLP zip Tied for Drop Weight Method
