3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply:
3.1.1
flexible dilatometer
cylindrical flexible probe which can be expanded by the application of hydraulic pressure or pressurized gas and which contains transducers for the measurement of the displacements of the flexible membrane and of the internal pressure
3.1.2
equipment for flexible dilatometer test
complete equipment which is necessary to carry out a flexible dilatometer test: the probe, a hydraulic pump or high-pressure gas in bottles, a measuring unit and cables to connect the probe to the measuring unit and the hydraulic pump or the gas bottle
NOTE The parts which are necessary to bring the flexible dilatometer probe to the testing point are not included.
3.1.3
dilatometer sounding
whole series of successive operations in a given borehole, i.e. forming dilatometer pockets and performing dilatometer tests in them
3.1.4
dilatometer test pocket
cylindrical cavity with circular cross-section drilled into the ground to receive the dilatometer probe
3.1.5
flexible dilatometer test
process of expanding the flexible dilatometer so as to press the flexible membrane against the pocket wall and so measure the associated expansion as a function of pressure and time (see Figure 1)
3.1.6
nominal diameter of the pocket
diameter of the pocket at the time of application of the seating pressure
3.1.7
seating pressure
pressure during the expansion of the dilatometer at which the dilatometer membrane contacts the pocket wall
3.1.8
pressure increment
fixed increase of pressure in the flexible dilatometer, according to a pre-determined programme and recorded in the control unit
NOTE It can also be a decrement.
3.1.9
diametral pocket displacement
displacement of pocket wall caused by an increase or decrease of any pressure
3.1.10
diameter increase/decrease
change in flexible dilatometer diameter and in pocket wall displacement caused by a pressure increment/decrement, and recorded in the measurement unit
3.1.11
flexible dilatometer curve
graphical plot of pressure versus the associated pocket wall displacement
3.1.12
flexible dilatometer shear modulus, GFDT
shear modulus calculated from the slope over various intervals of pressure and pocket wall displacement
3.1.13
flexible dilatometer modulus, EFDT
Young's modulus calculated from the slope over various intervals of pressure and pocket wall displacement
3.1.14
depth of test
distance between the ground level and the centre of the expanding length of the dilatometer measured along the borehole axis (see Figure 2)
3.1.15
operator
qualified person who carries out the test
3.2 Symbols and abbreviations
For the purposes of this document, the symbols given in Table 1 apply.
| Symbol | Description | Unit |
| a | Membrane compression coefficient in variant В dilatometer | mm.MPa–1 |
| d | Corrected pocket diameter | mm |
| d1 | Corrected pocket diameter at time t1 | mm |
| d2 | Corrected pocket diameter at time t2 | mm |
| dc | Compression calibration cylinder diameter | mm |
| dd | External diameter of the dilatometer | mm |
| dr | Pocket diameter as read at the measuring unit | mm |
| ds | Nominal diameter of the pocket after application of the seating pressure | mm |
| EFDT | Young's Modulus of flexible dilatometer test | MPa |
| G1 | Loading shear modulus in procedure С | MPa |
| GFDT | Shear modulus of flexible dilatometer test | MPa |
| GL | Loading shear modulus of flexible dilatometer test | MPa |
| Cr | Reloading shear modulus of flexible dilatometer test | MPa |
| GU | Unloading shear modulus of flexible dilatometer test | MPa |
| Gur | Unloading/reloading shear modulus of flexible dilatometer test | MPa |
| kf | Creep parameter | mm |
| LFD | Length of the expanding part of the probe | mm |
| Lg | Axial distance between transducer or LVDT section and membrane clamping ring | mm |
| Ld | Length of the measuring segment of the dilatometer | mm |
| p | Applied pressure after correction | MPa |
| p1.1 | Constant full relief pressure for loops in procedure A | MPa |
| p1 | Pressure at reversal point at first loop | MPa |
| p2 | Pressure at reversal point at second loop | MPa |
| p3 | Pressure at reversal point at third loop | MPa |
| pmax | Maximum applied pressure during a test | MPa |
| pm | Pressure loss associated with membrane stiffness | MPa |
| pLi | Range of applied pressure in loading phase no. i | MPa |
| pRi | Range of applied pressure in reloading phase no. i | MPa |
| pUi | Range of applied pressure in unloading phase no. i | MPa |
| pr | Pressure as read at the measuring unit | MPa |
| ps | Seating pressure | MPa |
| py | Yield pressure during dilatometer test in procedure С | MPa |
| t | Time | min |
| t1 | Time 1 of a constant pressure test | min |
| t2 | Time 2 of a constant pressure test | min |
| z | Test depth | m |
| Δdr | Increase of diametral displacement of the pocket | mm |
| Δd | Corrected increase of diametral pocket displacement | mm |
| Δрr | Increment of applied pressure as read on the control unit | MPa |
| Δр | Corrected increment of applied pressure | MPa |
| v | Poisson's ratio | — |
