13.4 Rotary sampling

13.4.1 Rotary sampling operation

(1)P Before commencement of rotary sampling category A or B in a predrilled borehole having an adequate diameter, the hole shall be cleaned out down to the initial sampling depth.

(2)P Before the core barrel is lowered down into the drillhole it shall be checked that

  • no friction occurs between the inner tube and the outer tube;
  • the distance between the tip of the inner tube and the core bit is according to specifications;
  • the drilling fluid will pass the sample at the right place - in case of face discharge only through the water tracks in the face of the cutter;
  • the pump pressure for circulating the drilling fluid is according to specifications.

(3)P During sampling the load on the cutter, the amount of circulated drilling fluid, and the rotation speed shall be checked complying with the specifications for the actual core barrel in use.

(4)P The penetration rate should be recorded based on time and core run progress.

(5)P The total penetration during one core run shall not exceed the net length of the inner tube or liner.

(6)P The core sample all be cut off from the stratum and the sampler retrieved without rotating the core barrel.

(7)P The sampler all be retrieved at uniform speed.

(8)P If using a rod handled core barrel, shocks on the sampling equipment, from disconnecting the rods, shall be avoided.

(9)P During withdrawal of the core from the barrel appropriate techniques to ensure that the core sample is not damaged or disturbed shall be applied.

(10)P After the sampling tube is disconnected from the core barrel the length of the recovered sample shall be measured and core losses, if any, determined.

13.4.2 Preservation, handling and storage of core samplers

(1)P After sampling and visual inspection has taken place cores from category A and B sampling methods shall be sealed immediately in case the natural water content is to be maintained.

(2) When using a liner the liner should be cut in a length suitable for placement of end caps with contact to the top and the bottom of the sample.

(3) When using core cases or pipes for transportation and storage the samples should be wrapped in a water tight film.

(4)P Samples shall be properly marked leaving no doubt about the top and bottom of the sample.

(5)P Cores from category A and B sampling methods shall be handled in such a way that no further disturbance will occur after withdrawal of the sample or during transportation and storage.

(6) Cores from category A and B sampling methods should be adequately protected from excessive heat, frost, vibration and shock during shipment and storage. Great care should be taken not to damage the seals of the samples and not to deform the packing.

(7) Cores from category A and B sampling methods should be stored during the shipment in a container and in the laboratory in a room where the temperature and humidity are kept constant.

13.5 Reporting of the core sampling operation

13.5.1 Labelling, preservation and handling of core samples

(1)P All samples shall be numbered, recorded and labelled immediately after being sealed.

(2)P The sample label shall show all necessary information about

  • identification data of the actual project;
  • date of the sampling;
  • number of the borehole;
  • sampling class and type of sampler used;
  • elevation or depths of the top and the bottom of the sample;
  • the length of the core run.

(3) The rock type, decomposition and possible discontinuities according to the visual examination should be given on the label, if possible.

13.5.2 Boring report

(1)P In addition to the requirements given in 2.6 the sampling report for boring in rock masses shall include the following essential data if applicable:

  • date of sampling;
  • position and elevation of boring location;
  • borehole direction: inclination and orientation;
  • whenever possible the depth of the free groundwater level;
  • the method of the preboring if used;
  • the use of casing and depth of the casing tip;
  • the use of drilling fluid and the level of the drilling fluid in borehole;
  • colour and colour shifts of drilling fluid;
  • loss, if any, of drilling fluid;
  • drilling fluid pressure and circulated volume;
  • the specifications and the type of sampler used;
  • the diameter or the size of the sample;
  • the depth (top and bottom of the sample) and the length of the sample;
  • the core run interval;
  • pressure on the cutting edge;
  • the rock mass type, discontinuities and grade of decomposition based on the visual examination of the sample by the field foreman and his judgement of the sampling category;
  • any obstructions and difficulties encountered during the sampling operation.

(2)P The sampling report shall be clear and accurate, and it shall not only contain the data required for determination of the rock strata and the location (x, y, z) of the samples obtained but also of any observations which will contribute to an estimate of the condition of the samples and the physical properties of the rock mass in situ.

(3) All unsuccessful sampling operation should be recorded.

Eurocode 7 Geotechnical design — Part 3: Design assisted by fieldtesting