Field report and GFDT results
The format of reporting the data may be freely chosen whereas the content of Table C.1 is mandatory (see 7.2). An example of plotted data is given in Figure C.1. An example of shear moduli GFDT obtained is given in Table C.2.
|Device serial No.:||Groundwater level
under surface .......... m
|Pocket from .......... m
To .......... m
|Measuring direction:||Remark:||Test operator:|
Data may be plotted according to Figure C.1. Corrected diameter d versus corrected applied pressure p in the three measuring directions is shown on three different graphs and the mean values of d are given on a fourth graph. Then various values of the ground shear modulus GFDT can be calculated for various ranges of pressures during loading and unloading (Table C.2) based on the data plotted on a figure similar to Figure 4.
- 1—3: plot of test data for each transducer
- (1 + 2 + 3)/3 : average of the 3 plots
|Range of applied pressure
|Shear moduli GFDT|
|Displacement transducer No. 1
|Displacement transducer No. 2
|Displacement transducer No. 3
|1–1||0,50 to 1,00||42||91||96||76|
|1–2||1,00 to 1,50||72||105||60||79|
|1–3||1,50 to 2,00||62||82||57||67|
|1–4||2,00 to 2,50||48||58||48||52|
|1–5||2,49 to 3,02||48||56||47||50|
|2–1||0,50 to 1,00||210||220||400||277|
|2–2||0,50 to 1,50||200||196||196||198|
|2–3||0,50 to 2,00||164||169||196||176|
|2–4||0,50 to 2,49||136||142||158||146|
|3–1||1,00 to 0,50||337||255||616||404|
|3–2||1,50 to 0,50||243||220||251||238|
|3–3||2,00 to 0,50||192||186||244||208|
|3–4||2,50 to 0,50||157||159||199||172|
|3–5||3,02 to 0,50||140||144||172||152|
Accuracy and uncertainties
D.1 Accuracy of the measuring devices
The accuracy of the measurements depends on the equipment and the type of measuring devices of pressure and displacement included in this equipment. The rules given in 5.4 shall be adhered to.
Because the readings for pressure and displacement are either recorded manually or by transducers, their resolution depends on either the display or the data logger. In both cases, the accuracy depends on how the various devices are calibrated. Therefore, the measuring devices shall be calibrated as close as possible to their measuring range increased by 10 % to 20 %.
D.2 Uncertainties of the measurements
The uncertainties of the measurements depend not only on the equipment. It is defined as the variability of the measurements obtained while measuring any magnitude. The higher the dispersion is, the higher is the uncertainty of the result.
The uncertainty is defined as the interval in which the real measurement of the magnitude is occurring; it is related to the repeatability of the measurements. It shall be calculated according to ENV 13005.
 EN 1997-1 Eurocode 7: Geotechnical design — Part 1: General rules
 EN 1997-2:2007, Eurocode 7: Geotechnical design — Part 2: Ground investigation and testing
 ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)