Civil Engineering Reference
In-Depth Information
a) Dilatometer test (pressuremeter)
Ground surface level
Section A - A through the borehole
A
A
5 - 10 d
Smooth borehole wall
Irregular borehole wall
d
b) Hydraulic fracturing
1
y
x
Pressure line for fracture creation
Hydraulically
created crack
(radial)
Pressure line for packers
z
Rubber packer
Pressurized fluid
2
2
z
Pressure zone
x
Hydraulically
created crack
(radial)
y
Rubber packer
Pressure transducer
Borehole
1
Figure 2.13
Schematic of the a) dilatometer and b) hydraulic fracturing tests
In these cases, it is necessary to secure the sides of the borehole or smooth
out the contours to allow the experiment to be conducted. This is usually
done with concrete or cement slurry resulting in an improvement of the
ground at the borehole but can lead to possible false results for the test.
In soft ground (soils and weak rock), there are three types of pressure-
meters available; a pre-bored pressuremeter (dilatometer type or Ménard type
- Ménard invented the original pressuremeter), a self-boring pressuremeter
and push-in pressuremeters. The pre-bored pressuremeters, typically 1 m long
and 74 mm diameter, are lowered into a slightly oversized pre-bored hole.
As the name implies, the self-boring pressuremeter bores itself into the ground,
