EASE OF COMPACTION
i) Apparatus:
The following apparatus is required
a) Open-ended cylinder 250mm long and
150 ± 6mm internal diameter (160mm
diameter unplastisized PVC pipe is suitable)
b) Metal rammer with striking face 40mm
diameter and weighing 1.0 ± 0.1kg
c) Rule
ii) Procedure
Obtain a representative sample (note 1) more than sufficient to
fill the cylinder (about 11kg). It is important that the moisture
content of the sample should not differ materially from that of
the main body of material at the time of its use in the trench.
Place the cylinder on a firm flat surface and gently pour the sample
material into it, loosely and without tamping. Strike off the top
surface level with the top of the cylinder and remove all surplus
spilled material. Lift the cylinder clear of its contents and place
on a fresh area of flat surface. Place about one quarter of the
contents back in the cylinder and tamp vigorously with the metal
rammer until no further compaction can be obtained. Repeat with
the second quarter, tamping as before, and so on for the third and
fourth quarter, tamping the final surface as level as possible.
Measure down from the top of the cylinder to the surface of the
compacted material. This distance in millimetres divided by the
height of the cylinder (250mm) is referred to as the "compaction
fraction".
Interpretation of results
TABLE 2
 |
|
Compaction fraction
(equivalent measurement
from the top of the cylinder, mm)
|
Suitability for use |
| <0.20 (50) |
Material Suitable |
| >0.20<0.3 (50 to 75) |
Material may be suitable for applications other than installation
carried out in compliance with the Civil Engineering Specification
for the Water Industry but requires extra care in compaction.
Not suitable if the ground is subjected to waterlogged conditions
after laying.
|
| >0.3 (75) |
Material Unsuitable |
PIPE LAYING
Unlike rigid pipes, pipes made from "flexible material"
such as PVCu cannot be classified by their "crushing strength"
but the fact that they are flexible does enable PVCu pipes to withstand
forces from external loads and ground movement.
When a vertical load is imposed on a "flexible pipe" the
resulting horizontal force is transmitted to the undisturbed trench
wall by the sidefill. Any deflection of the pipe will cease when the
horizontal reaction of the sidefill corresponds to the transmitted
vertical load and a state of equilibrium is reached.
FIGURE 6
MAXIMUM AND MINIMUM RECOMMENDED
DEPTHS
|
