What is a geotechnical survey (estudio geotécnico in Spanish)? It is a question many of us ask once we start worrying about the condition of our land. A good architecture practice in Málaga will arrange a study of this kind for you, so that you know whether you can build and on what terms. But what exactly does such a study involve?
Whenever you plan a civil engineering project or a particular building, the ground has to be investigated first. This step cannot be skipped: it is how you make sure the structure will not suffer from instability in the future. Understanding the ground — its many characteristics and how it behaves — is fundamental here.
A geotechnical survey is compulsory not merely as a matter of basic architectural and engineering prudence; it is also required by current regulations, specifically Royal Decree 314/2006 of 17 March, which approved the CTE (Spanish Technical Building Code). The Code’s basic document on foundations, DB-SE-C, sets out basic requirements that define the minimum acceptable levels of structural safety and quality. This type of study is sometimes also referred to as a topographical survey (estudio topográfico), although strictly speaking that term covers measuring levels and boundaries rather than investigating the ground itself.
What a geotechnical survey involves
When designing engineering or architectural works such as multi-family housing, studies of this kind are essential. Their main purpose is to establish the best and most suitable foundation for each specific building project.
Key factors
- The type of project you are about to undertake.
- The specific characteristics of the ground you want to build on.
Benefits
A good geotechnical survey carried out by experienced professionals offers a range of benefits, all of them well worth having:
- It prevents the loads on retaining structures and foundations from causing instability in the future.
- It allows the type and exact dimensions of the project to be defined as precisely as possible — one of the most important aspects of what a geotechnical survey is for.
- It helps prevent construction problems that could wreck the project, create health hazards or even lead to disaster: liquefaction, high water tables, landslides, expansive soils and so on.
How is a geotechnical survey carried out?
The process follows these steps:
- First comes what is known as the fieldwork (campaña in situ). The specialist visits the site and examines every aspect and condition of it: the topography, any slopes and watercourses, and so on. Several techniques are used to reach sound, unambiguous conclusions: trial pits (calicatas), excavations that yield representative samples of the ground; penetrometer tests; boreholes (sondeos), which extract samples using cylindrical core samplers; and standard penetration tests (SPT) to measure the strength of the ground.
- Next comes the laboratory stage (campaña en laboratorio), in which the samples obtained are analysed. This involves chemical analysis and particle-size analysis, which establishes the composition of the soil. The stage ends with mechanical tests to check the strength and stiffness of the ground materials.
- The last essential stage is, of course, writing the report. It sets out the results of the analyses on the nature and context of the ground, along with various recommendations for building on it and, naturally, an assessment of which foundation is most suitable in each case.
Understanding what a geotechnical survey is helps a great deal in knowing what to expect when you set out to build. It also sheds light on when you need a building permit (licencia de obras) and when to apply for it.
