3 Geotechnical data
(1)P Careful collection, recording and interpretation of geotechnical information shall always be made. This information shall include geology, geomorphology, seismicity, hydrology and history of the site. Indications of the variability of the ground shall be taken into account.
(2)P Geotechnical investigations shall be planned taking into account the construction and performance requirements of the proposed structure. The scope of geotechnical investigations shall be continuously reviewed as new information is obtained during execution of the work.
(3)P Routine field investigations and laboratory testing shall be carried out and reported generally in accordance with internationally recognised standards and recommendations. Deviations from these standards and additional test requirements shall be reported.
(4) Requirements for laboratory and field-testing should be taken from EN 1997-2.
3.2 Geotechnical investigations
(1)P Geotechnical investigations shall provide sufficient data concerning the ground and the ground-water conditions at and around the construction site for a proper description of the essential ground properties and a reliable assessment of the characteristic values of the ground parameters to be used in design calculations.
(2)P The composition and amount of the geotechnical investigations shall be adjusted to the particular investigation phase and the geotechnical category (see EN 1997-2, Section 2).
(3) For very large or unusual structures, structures involving abnormal risks or unusual or exceptionally difficult ground or loading conditions, and structures in highly seismic areas,it is possible that the extent of investigations specified in EN 1997 will not be sufficient to meet the design requirements.
(4) If the character and extent of the investigations are related to the Geotechnical Category of the structure, ground conditions that may influence the choice of Geotechnical Category should be determined as early as possible in the investigation.
(5) The investigations should include visual inspections of the site to enable the design assumptions to be verified during construction.
3.2.2 Preliminary investigations
(1)P Preliminary investigations shall be carried out:
- to assess the general suitability of the site;
- to compare alternative sites, if relevant;
- to estimate the changes that may be caused by the proposed works;
- to plan the design and control investigations, including identification of the extent of ground, which may have significant influence on the behaviour of the structure;
- to identify borrow areas, if relevant.
3.2.3 Design investigations
(1)P Design investigations shall be carried out:
- to provide the information required for an adequate design of the temporary and permanent works;
- to provide the information required to plan the method of construction;
- to identify any difficulties that may arise during construction.
(2)P The design investigation shall identify in a reliable way the disposition and properties of all ground relevant to or affected by the proposed construction.
(3)P The parameters, which affect the ability of the structure to satisfy its performance criteria shall be established before the start of the final design.
(4) In order to ensure that the design investigation covers all relevant ground formations, particular attention should be paid to the following geological features:
- ground profile;
- natural or man-made cavities;
- degradation of rocks, soils, or fill materials;
- hydrogeological effects;
- faults, joints and other discontinuities;
- creeping soil and rock masses;
- expansible and collapsible soils and rocks;
- presence of waste or man-made materials.
(5)P The history of the site and its surroundings shall be taken into account.
(6)P The investigation shall be carried out at least through the formations, which are assessed as being relevant to the project.
(7)P The existing ground-water levels shall be established during the investigation. Any free water levels observed during the investigation shall be recorded (see EN 1997-2).
(8) The extreme water levels of any water source, which might influence the ground-water pressures should be established.
(9)P The location and capacities of any dewatering or water abstraction wells in the vicinity of the site shall be established.