Standards for geotechnical investigation and testing Eurocode Part

Eurocode 7 - Geotechnical design, Part 2 - ground investigation and testing2 is divided into six sections and twenty-four annexes, as illustrated in Figure 4.1 and Plate 6 (in the book's colour section).

§2 Planning of ground §1 General Investigations §3 Soil and rock

5% 7% sampling and

Annexes A-X 52%

§6 Ground investigation report 2%

Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version.

§2 Planning of ground §1 General Investigations §3 Soil and rock

5% 7% sampling and

VI J- groundwater

/ / measurements

Annexes A-X 52%

§6 Ground investigation report 2%

Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version.

EN 1997-2 provides detailed rules for site investigations, general test specifications, derivations of ground properties and the geotechnical model of the site, and examples of calculation methods based on field and laboratory testing.

4.1.2 Complementary standards

EN 1997-2 refers extensively to a new suite of international and European standards, prepared jointly by ISO technical committee TC 182 and CEN TC 341, as summarized in Figure 4.2.

Geotechnical Investigation
Figure 4.2. Complementary geotechnical investigation and testing standards

Two of these groups of standards (EN ISOs 14688 and 14689) are concerned with the identification and classification of soil and rock and are discussed in Sections 4.3 and 4.4 below.

Four of the groups of standards (EN ISOs 22282, 22475, 22476, and 22477) cover field testing and are discussed in Section 4.7.

Finally, one group of standards (EN ISO TS 178923) deals with laboratory testing and is discussed in Section 4.7.6.

Each of the standards within each group is divided into a number of parts, as shown in the outer ring of Figure 4.2. The entire suite comprises nearly fifty standards or specifications.

The relationship between EN 1997-2 and these complementary standards is shown in Figure 4.3. The diagram shows which sections of EN 1997-2 refer to which EN ISO standard.

4.2 Planning ground investigations 4.2.1 Aims of a geotechnical investigation

The aims of a geotechnical investigation are to establish soil, rock, and groundwater conditions; determine the properties of soils and rocks; and gather additional relevant knowledge about the site.

According to Eurocode 7 Part 1:

Geotechnical investigations shall provide sufficient data concerning the ground and the ground-water conditions ... for a proper description of the essential ground properties and a reliable assessment of the characteristic... ground parameters to be used in design calculations.

The scope of geotechnical investigations is illustrated in Figure 4.4.

According to EN 1997-2, preliminary investigations must allow the engineer to assess the general suitability of the site, compare alternative sites, estimate changes caused by the proposed works, identify any borrow areas, and plan the subsequent design and control investigations. These tasks (which are Principles) are boxed in Figure 4.4.

Figure 4.3. Links between EN 1997-2 and its complementary standards

j assess general suitability of the site | compare alternative sites J estimate changes caused by proposed works

| plandesign and control investigations |—y including extent of ground having significant influence on structure's behaviour

{kfentify barrow" assess suitable positioning of structure ■ evaluate possible effects on neighbouring buildings and sites ■ consider possible foundation methods and ground improvements ■

provide description of ground conditions relevant to proposed works establish basis for assessment of geotechnical parameters

Preliminary V investigations field investigations field investigations

■{Ground investigations~-

, drilling/excavations for sampling f groundwater measurements Wield tests of temporary works

Geotechnical investigations

-laboratory testing -desk studies -control and monitoring of permanent works

{provide information for planning method of construction {identify difficulties that may arise during construction identify disposition and properties of all ground relevant to or affected by construction

of permanent works identify disposition and properties of all ground relevant to or affected by construction

Geotechnical Desk Study

History of development of site~{

Appraisal of existing constructions of prime importance in observational method

History of development of site~{

^Geotechnical Category^

Figure 4.4. Scope of geotechnical investigations

Preliminary investigations should allow the engineer to assess a suitable position for the structure; evaluate its possible effects on adjacent buildings; and consider possible foundations and ground improvements.

Design investigations must provide information for designing temporary and permanent works and for planning the construction method; identify difficulties that may arise during construction; and identify the disposition and properties of all ground relevant to or affected by the construction.

Control investigations are used to monitor and control construction and are of prime importance in the Observational Method4 of design.

As Figure 4.4 indicates, geotechnical investigations may involve ground investigations (i.e. desk studies, field investigations, and laboratory testing), appraisal of existing constructions, and research into the site's historical development. The amount of investigation needed is related to the Geotechnical Category to which the project has been assigned.

In many situations only one investigation will be performed as the budget available for investigation is small or the project size does not warrant staged investigation. In these circumstances the aims of the preliminary and design investigations must be fulfilled by one investigation.

4.2.2 Spacing of investigation points

Annex B.3 of EN 1997-2 provides guidance on the spacing of investigation points for geotechnical investigations, as summarized in the table below.

Structure

Spacing

Arrangement

High-rise and industrial

15-40m

Grid

Large area

< 60m

Grid

Linear roads, railways, channels, pipelines, dikes, tunnels, retaining walls

20-200 m

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