A geotechnical investigation to rely on.
Got Questions? We’ve Got Answers!
How are the extent and depth of a geotechnical investigation defined?
The extent (number of bore holes or penetrometer tests) of a geotechnical investigation is defined in the case of building projects by the National Seismic Design Code (EAK-2000) depending on the seismicity of the area of interest (I, II or III), the class of the seismic hazard of the foundation soil (A, B, Γ, Δ or Χ) and the significance of the structure (Σ1, Σ2, Σ3 or Σ4). In the case of marine projects, this is defined depending on the length of the quay platforms. On the contrary, there is no regulatory provision for the required depth of investigation in the case of building projects, which in the case of marine projects this is a function of the sea depth in the area of construction of the facility.
Nevertheless, based on current practice, for the optimum representation of the prevailing geotechnical conditions in the area of interest, the minimum required number of investigation spots (bore holes or penetrometer positions) is three (3), preferably arranged in a triangular grid.
When is a geotechnical investigation required?
The requirement for the execution of a geotechnical investigation for buildings and its extent are defined in the National Seismic Design Code (EAK-2000) depending on the seismicity of the area of interest (I, II, or III), the class of the seismic hazard of the foundation soil (A, B, Γ, Δ or Χ) and the significance of the structure (Σ1, Σ2, Σ3 or Σ4).
Even though this is not mandatory, it is important to be acknowledged that with appropriate and timely investigation of the geotechnical conditions of a project it is possible to save time and money not only during construction, by reducing the unexpected problems (high water table, problems and delays during excavation and concreting of the foundation and the underground floors, inferior foundation soil, unsupported slopes and failures, settlement issues of adjacent structures) but during the lifetime and operation of the project as well. The latter is achieved by reducing the possibilities of cracks and displacements of the bearing structure, due to settlement or expansion of the foundation soil, high humidity and water intrusion within the underground spaces, as a result of underestimating the true level of the ground water table.