3.4 Ground Investigation Report
3.4.1 Requirements
(1)P The results of a geotechnical investigation shall be compiled in a Ground Investigation Report, which shall form a part of the Geotechnical Design Report described in 2.8.
(2)P Reference shall be made to EN 1997-2 for information on the use of laboratory and field tests for geotechnical parameters.
(3) The Ground Investigation Report should normally consist of:
- a presentation of all available geotechnical information including geological features and relevant data;
- a geotechnical evaluation of the information, stating the assumptions made in the interpretation of the test results.
The information may be presented as one report or as separate parts.
3.4.2 Presentation of geotechnical information
(1)P The presentation of geotechnical information shall include:
- a factual account of all field and laboratory work;
- documentation of the methods used to carry out the field investigations and the laboratory testing.
The documentation shall be based on the test reports described in EN 1997-2.
(2) In addition, the factual account should include the following information, as relevant:
- names of all consultants and subcontractors;
- purpose and scope of the geotechnical investigation;
- dates between which field and laboratory work was performed;
- field reconnaissance of the general area of the project noting particularly:
- evidence of ground-water;
- behaviour of neighbouring structures;
- exposures in quarries and borrow areas;
- areas of instability;
- difficulties during excavation;
- history of the site;
- geology of the site, including faulting;
- survey data;
- information from available aerial photographs;
- local experience of the area;
- information about the seismicity of the area;
- procedures used for sampling and transportation and storage of samples;
- types of field equipment used;
- tabulation of quantities of field and laboratory work, and presentation of field observations, which were made by the supervising field personnel during the subsurface explorations;
- data on fluctuations of any ground-water table with time in the boreholes during the performance of the field work and in piezometers after the completion of the field work;
- compilation of boring logs, including photographs of the cores, with descriptions of subsurface formations based on field descriptions and on the results of the laboratory tests;
- the occurrence, or the possibility of occurrence, of radon;
- data on frost susceptibility of soils;
- grouping and presentation of field and laboratory test results in appendices.
3.4.3 Evaluation of geotechnical information
(1)P The evaluation of the geotechnical information shall include as appropriate:
- a review of the field and laboratory work. Any limitations in the data (e.g. defective, irrelevant, insufficient or inaccurate) shall be pointed out and commented upon. The sampling and sample transportation and storage procedures shall be considered when interpreting the test results. Any particularly adverse test results shall be considered carefully in order to determine if they are misleading or represent a real phenomenon that must be accounted for in the design;
- a review of the derived values of geotechnical parameters;
- any proposals for necessary further field and laboratory work, with comments justifying the need for this extra work. Such proposals shall be accompanied by a detailed programme for the extra investigations to be carried out with specific reference to the questions that have to be answered.
(2) In addition, the evaluation of the geotechnical data should include the following, if relevant:
- tabulation and graphical presentation of the results of the field and laboratory work in relation to the requirements of the project and, if deemed necessary,
- histograms illustrating the range of values of the most relevant data and their distribution;
- depth of the ground-water table and its seasonal fluctuations;
- subsurface profile(s) showing the differentiation of the various formations;
- detailed descriptions of all formations including their physical properties and their deformation and strength characteristics;
- comments on irregularities such as pockets and cavities;
- the range and any grouping of derived values of the geotechnical data for each stratum.
