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Part C - Minimum Requirements on geotechnical investigations
• the foundation proposal; it shall be shown in a suitable manner in the soil and foundation
expertise (development phase) that the verification for structural safety and suitability for
use of the foundation elements can be carried out as part of these foundation proposal.
These illustrations are not necessary in the soil and foundation expertise in the construction
phase as the verifications are included in the geotechnical design report in accordance with
DIN EN 1997-1,
• notes for taking building ground behaviour under cyclical loads into account for further
planning,
• if applicable, information about geological hazards (e.g. gas, earthquakes) and
• details concerning execution of construction.
4.3.2 Information provided in the soil and foundation expertise
The results compiled in the geotechnical site survey report provide the basis for the soil and
foundation expertise to be prepared by the geotechnical expert. Together, both reports form
the geotechnical report in accordance with DIN 4020 in the respective project phase.
The soil and foundation expertise shall contain a synoptic description of the geological structure,
the properties of on-site soil strata identified, and of the physical soil characteristics, and
an evaluation of the ground under static/engineering aspects as well as civil engineering aspects.
An indispensable part of the expertise is information about grain size distribution, the
compactness of non-cohesive soils, condition of cohesive soils, the illustration of separation
plans (Frequency, degree of separation, solidity and width of openings in the joints) and evaluation
of the shear parameters and coefficients of stiffness in the geotechnical site survey report
with regard to the requirements to be met. One or several calculation profiles must be
drawn up for each structure, if required.
The soil and foundation expertiese specifies the characteristic soil parameters that are relevant
to the static analysis, at least the densities, stiffness moduli, and shear parameters as
well as for static soil analyses in limit conditions of load-carrying properties and suitability for
use and for limit values for foundation movement. Before establishing the characteristic rock
parameters it must be decided whether a discontinuum (a solid model with trend surfaces) or
a continuum (solid model with similar mechanical properties) is used for rocks that feature
trend surfaces as a computation model. When establishing characteristic parameters anisotropy
and inhomogeneities of the rock must be taken into consideration along with the expected
direction of load. If required, the geotechnical expert may first discuss and agree these
values with the developer, the design engineer, the responsible construction supervising authority
or certification body in terms of the Standard Design, possibly also with the construction
company taking into account tasks and requirements.
The soil and foundation expertise shall include a classification of soils by soil groups according
to DIN 18196 and soil classes according to DIN 18300 and 18311.
The geotechnical expert shall prepare a recommendation for the foundation design. Also, an
evaluation of soil properties with respect to piling and the installation of mudmats shall be part
of the ground and foundation expertise. If the scope of investigations performed does not allow
such an evaluation to be made, this should be pointed out in a note, and additional investigations
should be proposed and performed at a later date.
Finally, the soil and foundation expertise shall also assess the risk of encountering obstructions
to driving. In this context, not only the results of borings and penetration tests should be
taken into account but particularly the results of the geological-geophysical study.
