2.1 General (p. II)

(14)P The results of the desk studies and the site inspection shall be considered, when locating the various investigation points. Investigations shall be targeted at points representing the variation in ground conditions for soil, rock and groundwater.

(15)P In cases where more than one type of investigation shall be made at a certain location (e.g. CPT-test and piston sampling), the boreholes shall be placed at least 2 m apart.

(16)P The depth of investigation shall include all relevant layers for the actual geotechnical design.

(17)P The selection of the location of boreholes and test pits shall take account of possible adverse effects on the integrity of the construction to be built and neighbouring structures and shall minimize the probability of harmfull environmental effects.

(18)P The class and number of samples shall be based on the aim and status of the soil investigations, on the geology of the site and on the complexity of the geotechnical structure and of the construction to be designed.

(19)P Sampling shall be done in accordance with sections 12 and 13.

(20) Where lamination or fine stratification of the subsoil can influence the geotechnical design, consideration should be given to the use of continuous boring with open tube sampler or core drilling. Additional samples may be taken with e.g. a short open tube sampler, a fixed piston sampler or a block sampler.

(21) In case there is no stratification or no influence from stratification, in coarse soils, samples from auger or bailer may be sufficient. In clays and organic soils high quality samples should be taken with special equipment.

(22) Laboratory investigations for classification purposes and determination of the properties of the soil or rock should be performed as relevant for the project as a part of the total ground investigation programme. Guidance on the choice of investigation methods in order to obtain various properties of soil and rock may be found in paragraphs (23) to (26).

(23) Suitable routine classification for soil samples with various degrees of disturbance is presented in table 2.1. The routine tests are generally performed in both the preparatory and the design investigation phases. However, in the preparatory phase a limited number of samples may often be investigated.

Table 2.1: Routine soil classification tests

Soil type	Clayey soils			Silty soils			Sandy, gravely soils
Sample quality	Undis– turbed	Dis– turbed	Re– moul– ded	Undis– turbed	Dis– turbed	Re– moul– ded	Dis– turbed	Re– moul– ded
Parameters
Soil class Water content, (w) Density, (D) (D_max), (D_min) Atterberg limits Grain size distribution Undrained shear strength, (c_u) Sensitivity, (S_t)	X X X – X (X) X X	X (X) (X) – X (X) – –	X (X) – – X (X) – –	X X X (X) X X (X) –	X (X) (X) (X) X X – –	X (X) – (X) X X – –	X (X) – X – X – –	X (X) – X – X – –
X = normal to determine; (X) = possible to determine; – = not applicable.

(24) In addition to these routine tests for soils other classification tests for certain cases may be performed e.g. activity, density of grain material and organic content.

(25) Laboratory tests to determine various geotechnical parameters for design purposes are indicated in table 2.2.

Table 2.2: Laboratory tests for the determination of certain geotechnical parameters

Geotechnical parameter	Type of soil
Geotechnical parameter	Gravel	Sand	Silt	NC clay	OC clay	Peat organic clay
Oedometer modulus (E_oed)	OED^**)	OED^**)	OED	OED^*)	OED	OED^*)
Effective shear strength (c'), (φ')	TX, DSS, (DST)	TX, DSS, (DST)	TX, DSS, (DST)	TX, DSS, (DST)	TX, DSS, (DST)	TX, DSS, (DST)
Undrained shear strength (c_u)			TX, SIT, DSS, (DST)	TX, SIT^*), DSS, (DST)	TX, SIT^*), DSS, (DST)	TX, SIT^*), DSS, (DST)
Permeability (k)	PT(C), SV	PT(C), SV	PT(C), PT(F)	PT(F)	PT(F)	PT(F)
^) Indicate investigations normally performed in the preliminary phase, at least to some extent. ^*) Requires special device.

Abbreviations of laboratory tests:

OED

Oedometer test

Triaxial test

PT(F)

Permeability test (falling head)

PT(C)

Permeability test (constant head)

DST

Direct shear test

SIT

Strength index tests

Sieving

DSS

Direct simple shear test

(26) Suitable routine laboratory tests for rock samples are presented in table 2.3. These tests normally give the necessary basis for the description of the rock material.

Table 2.3: Routine rock tests

Type of test	Type of rock^***)
Type of test	1	2	3	4
Geological classification Unit weight, (γ) Water content, (w) Porosity, (n) Uniaxial compressive strength test Point load test Compressibility, (E)	X X X X X X X	X X X X X X X	X X X X X X X	X X X X X X X
^***) Group according to ENV 1997-1, Annex E, Table E.1.

(27) The classification of core samples will normally comprise a geological description, the core recovery, the Rock Quality Designation (RQD), the degrees of induration, weathering and fissuring. For weathering classification see annex L. In addition to the routine tests in table 2.3 for rocks other tests may be selected for different purposes, e.g. density of grains, wave velocity, Brazilian tests, shear strength of rock and joints, slake durability tests, swelling tests and abrasion tests.

(28) The properties of the rock mass including the layering and fissuring normally may indirectly be investigated by compression and shear strength tests along joints. In weak rocks complementary tests in the field or with large scale laboratory tests on block samples may be made.