top of page


  • Inconsistent : stony d> 40 mm - weevil (KW), loam (KWg), rubble (KR), clay rubble (KRg), pebbles (KO) coarse-grained 2 <d ≤ 40 mm - gravel (Ż), clay gravel ( Żg), salt sand (Po), clay sand salt (Pog), coarse sand (Pr), medium sand (Ps), fine sand (Pd), dusty sand (Pπ)

  • Cohesive : fine-grained d ≤ 2 mm - loamy sand (Pg), sandy dust (πp), DUST (π), sandy loam (Gp), clay (G), silty loam (Gπ), compact sandy loam (Gpz), clay compact (Gz), compact silt (Gπz), sandy loam (Ip), loam (I), silty loam (Iπ) [d] - Range of equivalent diameters




  • Load - bearing capacity - soil resistance which it opposes to the pressure of the building (structure). This is the relationship between the load on the part of the foundation and the deformation of the soil foundation.

  • Compressibility - the phenomenon of changes in the volume of soil under the pressure exerted by the foundation. Note: the higher the moisture content of the cohesive soil, the lower the friction forces between the grains, and consequently the greater the settlement of the object. The greater the moisture of the cohesive soil, the greater the degree of unfavorable compaction (plasticizing or liquefying the material).

  • Freezing - volume increase caused by freezing of the water contained in the pores of the framework ground. As a result, the soil swells and lifts the building standing on it (damage due to this is e.g. breaking foundation benches, cracking walls, continuous and discontinuous deformations of road surfaces).



  • Macroscopic (in situ): determination of soil type (coherent or non-cohesive) by means of tests: rolling, grinding, wetting. Initial assessment of soil moisture: dry - does not moisten paper; moist - moisturizes the paper; wet - releases water when squeezed; hydrated - water leaks spontaneously. visual determination of the soil color in the state of natural humidity; determination of CaCO3 content with hydrochloric acid.

  • Laboratory - to determine: apparent density, soil skeleton properties, porosity, humidity, granulometric and mineralogical composition, content of organic parts, mechanical properties (primarily strength and compressibility). identification of building substrates by means of opencasts, sounding (penetration of the probe along with determination of soil resistance) or test holes for profiling purposes. Required drilling depth - 7 meters below the designed depth of the foundation.

4. REGULATION OF THE MINISTER OF HOME AFFAIRS AND ADMINISTRATION regarding the establishment of geotechnical conditions for the foundation of buildings.
§ 7. The following geotechnical categories are distinguished:

1) the first geotechnical category , which includes small buildings with a statically determinate calculation scheme, in simple soil conditions, for which a qualitative determination of soil properties is sufficient, such as:

  • 1- or 2-storey residential and farm buildings,

  • retaining walls and expansion of excavations, if the difference in levels does not exceed 2 m,

  • excavations to a depth of 1.2 m and embankments up to a height of 3 m, performed especially in road construction, drainage works and laying pipelines,

2) the second geotechnical category , which includes construction works in simple and complex ground conditions, requiring quantitative assessment of geotechnical data and their analysis, such as:

  • direct or deep foundations,

  • retaining walls or other retaining structures, subject to point 1 lit. b), keeping ground or water,

  • excavations and embankments, subject to point 1 lit. c) and earthworks,

  • bridgeheads and pillars and quays,

  • ground anchors and other anchoring systems,

3) the third geotechnical category , which includes:

  • unusual construction objects, regardless of the complexity of the ground conditions, the implementation or use of which may pose a serious threat to users and the environment, such as: nuclear power facilities, refineries, chemical plants, water dams, or whose construction projects contain new, not tested in national practice , technical solutions not found in regulations and Polish Standards,

  • building structures erected in complex soil conditions,

  • historic and monumental buildings.

bottom of page