5 Test procedure

5.1 Safety requirements

Regarding environmental protection, national standards and local regulations shall be applied as long as respective international standards are not available.

National safety regulations shall be followed, for instance for:

  • personal health and safety equipment,
  • clean air if working in confined spaces,
  • ensuring the safety of the equipment.

Drill rigs shall be in accordance with EN 791 and EN 996.

5.2 Assembly of parts

The membrane and other parts of the probe shall be selected according to the expected ground conditions. Then the probe shall be linked to the control unit through the connecting line/cable.

The system shall be filled with the working fluid.

5.3 Calibration of the testing device and corrections of readings

5.3.1 Calibration of the testing device

Before testing, the equipment shall have been calibrated (see Annex A). The following components of the equipment shall be calibrated:

  • displacement measuring system;
  • pressure measuring system.

The calibration of the data logger system shall be conducted according to ISO 10012. If any part of the system is repaired or exchanged, the calibration shall be verified. Copies of the calibration documents shall be available at the job site.

5.3.2 Correction of readings

Corrections as described in A.2 shall be performed for variant A and B probes, taking into consideration the maximum deformation expected in the test.

In the case of variant B, also the corrections as described in A.3 shall be applied.

5.4 Uncertainties of measurement

The following uncertainties shall be achieved in accordance with ISO 10012 (see also Annex D):

  • a) the distance between the centre of the membrane and the top of the pocket shall not exceed
    • 0,1 m, or
    • 1/200 of the length of the rod string, whichever is the greater.
  • b) the resolution of each sensor used for the measurement of the additional diametral displacement Δdr shall be
    • 5 μn;
  • c) the resolution for pressures shall be
    • < 0,5 % of the measured pressure, or
    • < 20 kPa, whichever is the greater;
  • d) the resolution for time intervals shall be
    • 1 s.

5.5 Preparation for the sounding

The test location is usually determined from design requirements. The position of the borehole into which the probe is to be inserted shall be marked on a drawing and identified by its location details. When the borehole is inclined, its slope and direction should be recorded

For each borehole, the following parameters shall be recorded:

  • reference to ISO 22476-5;
  • sounding number;
  • technique of borehole drilling;
  • soil/rock profile or at least the soil/rock type for each test pocket according to ISO 14688-1 and ISO 14689-1.

5.6 Pocket drilling and device placing

The pocket shall be drilled and the dilatometer probe placed in the test location with the minimum of disturbance to the borehole wall to be tested.

The pocket shall be drilled and samples taken according to ISO 22475-1. Identification and classification of the ground according to ISO 14688-1 and ISO 14689-1 shall be available from every separate ground layer within the desired investigation depth (see EN 1997-2:2007, P, 4.1 (1) P and 4.2.3(2) P).

The borehole shall be advanced to within 1 m of the test depth. A pocket of about 3 m length shall then be cored at the nominal diameter for the instrument. The dilatometer probe shall be placed without delay. In all but hard rock, it shall be in position no later than 2 h after finishing the coring operation. If necessary, the instrument may be orientated in the pocket by rotating the setting rods. The instrument shall enter the pocket so that the top of the expanding length is at least 0,5 m from the pocket entry. The lower edges of the flexible dilatometer membrane shall not be closer than 0,5 m to the bottom of the pocket.

Careful attention shall be given to the effects of any sedimentation in the borehole.

Where no core has been recovered or when the stability of the borehole wall is not guaranteed, the decision of performing a test shall be evaluated by the operator.

When measures are taken to stabilize the borehole wall, their influence shall be considered when evaluating the test results.

5.7 Test execution

5.7.1 Test procedure and loading programmes

One of the following procedures, each representing a specific loading programme, may be chosen to carry out the test (see Annex B):

  • Procedure A: load, unload and reload cycles. The data are recorded manually.
  • Procedure B: load, unload and reload cycles. The data are recorded automatically.
  • Procedure C: only one loading phase. The data are recorded manually.
  • Procedure D: only one loading phase, followed by an unload/reload loop which is then followed by a pressure hold of an appreciable length of time during which the corrected pressure shall be maintained constant. The data are recorded manually.

The test procedure and its loading/unloading programme shall be selected according to the intended use of the test results.

5.7.2 Readings and recordings before and during the test

A comprehensive number of data (see 7) such as listed in to shall be reported. Before the test

  • test operator identification;
  • type of probe;
  • method of probe setting;
  • calibration test references;
  • depth (z) of the probe;
  • if a data logger is used, its parameters;
  • pressurizing and read-out unit number;
  • memory card number or disk number;
  • the initialization of the data logger if the data are not recorded manually;
  • the initial reading of each transducer is checked and recorded;
  • year, month, day, hour and minute of test. During the test

At the end of each pressure hold:

  • loading pressure or hold number in the series;
  • any changes in the pressure and displacement occurring during the hold. At test completion (see 5.8)

  • date and time at completion of test;
  • the uncorrected pressure versus displacement curve;
  • the full print-out authentication by the operator, who signs and gives his full name in capital letters. Data sheet and print out

Data sheets (see e.g. Annex C) or, in case of the use of a data logger, print outs shall be available for reporting the results.

5.8 End of loading

All tests stop when any of the following occur:

  • the specified test programme has been carried out; or
  • the maximum admissible expansion of the flexible dilatometer membrane is reached; or
  • the measuring range of any of the transducers is exceeded.

5.9 Back-filling of borehole

After completion of all the tests in a sounding, the borehole shall be back-filled and the site restored according to the specifications given in ISO 22475-1.

ISO 22476-5:2012 Field testing — Part 5: Flexible dilatometer test