68
soil. These two readings serve as a basis for predicting several
important geotechnical parameters, using experimentally and semi-
empirically derived correlations (17,50,68). The DMT sounding provides
indications of soil type, preconsolidation stress, lateral stress ratio
at rest (KQ), Young's modulus (E), constrained modulus (M), shear
strength in clays and angle of shearing resistance in sands.
The major components of the dilatometer test equipment are the
dilatometer blade, the gas-electric connecting cable, a gas-pressure
source, and the read-out (control) unit. Figure 3.4 shows a schematic
diagram of this equipment. In addition there is a calibration unit,
adaptors, electric ground cable and a tool kit containing special tools
and replacement parts. Detailed descriptions and functions of the
various components are presented by Bullock (17) and Marchetti and
Crapps (69).
The dilatometer blade, as shown in Figure 3.4, consists of a stain
less steel blade, 94 mm wide and 14 mm thick, bevelled at the bottom
edge to provide an approximate 16-degree cutting edge. A 60 mm stain
less steel circular membrane is centered on and flush with one side of
the blade.
The control unit, housed in an aluminum carrying case, contains
various indicators, a pressure gauge and the controls for running the
test. The control unit gauge used in the current study had a range of
0-40 bars. Higher and lower range units are also available. This gauge
provides the gas pressure readings for the dilatometer test.
The dilatometer blade is advanced into the ground using standard
field equipment. The blade can be pushed or driven by one of the
following methods (29):