2.2 Definitions

(1)P dynamic sounding or probing: driving a penetrometer into the ground with a hammer or a percussion drilling machine while measuring the resistance in e.g. blows or seconds for a certain amount of penetration.

(2)P field investigations for geotechnical purposes: geophysical investigations, penetration tests, in situ testing, soil sampling, rock sampling, groundwater measurements, large scale tests and monitoring.

(3) Examples of the various types of field investigations are:

  • geophysical investigations (e.g. seismic profiling, ground penetrating radar, resistivity measurements and borehole logging);
  • penetration testing (e.g. CPT, SPT, static soundings and dynamic probings);
  • in situ testing (e.g. pressuremeter tests, dilatometer tests, plate load tests, field vane tests and permeability tests);
  • soil and rock sampling for description of the soil or rock and laboratory tests;
  • groundwater measurements to determine the groundwater table or the pore pressure profile and their fluctuations;
  • large scale tests in order to determine e.g. the bearing capacity and behaviour of elements directly;
  • monitoring of the behaviour of different constructions e.g. movement of anchored retaining structures, settlement of foundations, pore water dissipation beneath embankments etc.

(4)P investigation point: the co-ordinates (x, y, z) where one or a number of different tests or a sampling is performed.

(5)P large scale tests: tests to determine directly the bearing capacity and behaviour of plates, piles, ground anchors or the transmissivity of the ground by pumping tests.

(6)P measuring While Drilling (MWD): technique of measuring a number of boring parameters during soil-rock sounding. Both manual and automatic recording exists.

(7) During drilling for example the penetration rate, rate of rotation, bit force, torsional moment, flush pressure and volume of flushing agent can be measured.

(8)P penetration test: all different tests where a rod provided with a tip is pushed or driven into the ground while the resistance to penetration is recorded.

(9) Penetration tests thus include both static and dynamic penetration tests and sounding methods such as CPT, WST, SPT, DP and soil-rock sounding (SR) in accordance with definitions in the following sections.

(10)P preliminary investigation: investigations performed before designing and specifying an investigation programme, including desk studies and site inspection.

(11)P soil or rock layer: layer of normally uniform material with similar properties, extending over a certain area in the ground.

(12)P soil-Rock Sounding: dynamic probing through possible soil into the rock with a percussion drilling machine and normal rock drilling tools and possibly MWD-technique.

(13)P static sounding: pushing or rotating a statically loaded penetrometer through the soil while the resistance is measured in e.g. kN or for the weight sounding test in halfturns per 0,2 m of penetration.

2.3 Preliminary investigations for positioning of a structure and preliminary design

(1)P A preliminary soils investigation for positioning of the structure and preliminary design shall supply estimates of soil data concerning:

  • type of soil or rock and their stratification;
  • thickness and relative density or strength of the soil;
  • groundwater table or pore pressure profile;
  • preliminary strength and deformation properties for soils and rock;
  • the occurrence of contaminated ground or groundwater that might be hazardous to health or the durability of construction material.

(2)P In cases where the overall stability of the site may be of concern, a preliminary investigation shall be made.

(3) The slope stability investigation should be performed in the assumed most unfavourable section and the surrounding area where previous failure may have occurred. The volume to be investigated should cover at least a depth down to 5 m below potential slip surfaces.

(4) A slope stability investigation in soil should comprise: surveying, penetration tests, sampling, in situ tests, groundwater measurements and laboratory testing.

(5) Rock slope investigations in addition should comprise a site inspection with mapping of discontinuities and determination of the strength of joints.

(6)P In the preliminary investigation phase the investigation points shall be distributed over the area, in such a way that an adequate picture is derived of the variability of the site with regard to the stratification and quality of the ground and of the groundwater situation.

(7)P When parts of the soil and/or the structure are particularly complex the preliminary investigation shall be focussed on the concerned part of the building site.

(8) The influence on or effect of surrounding constructions shall be considered when defining the preliminary investigation programme.

(9) The extend of the preliminary soils investigation should as a minimum contain three investigation verticals equally distributed in a respective cross-section of the building site. This investigation may comprise penetration tests, in situ testing, boring for sampling (in the weakest soil) and ground water measurements where the most unfavourable groundwater level may be expected.

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