In urban areas there is a very complex underground infrastructure (utilities, foundations) that could be damaged in case of not having identified them before. Sometimes plans do not show them either, so project safety and feasibility depend on a good preparation upfront i.e. identifying potential obstacles.
The Ground Penetrating Radar (GPR) is a geophysics prospecting technique based on sending out electro-magnetic signals into the ground by means of an antenna. It is an indirect and non-invasive technique as it does not require excavations and interventions in the ground at all. Changes in the subsoil produce signal reflections that can be detected by the device on surface based on time. This information can be collected and processed by specific programmes. Its main advantages are promptness, high resolution and high quality up to -3m depth.
Studies for piping by drilling
Studies for trenches:
All elements that could affect the drilling works (geographic limits, roads, rivers) are identified upfront.
Before geophysics study topographic works are carried out.
The electrical tomography technique (or resistivity pictures) can identify subsoil materials based on the distribution of their electrical characteristics.
This method consists of injecting an electrical direct current into the ground by means of several electrodes. Characterisation of underground material can be obtained after measuring intensity and voltage. This method is an evolution of the vertical electrical sounding (VES) technique, where a series of resistivity measures can be gathered by combining multiple electrodes. The final results are sections of apparent resistivity at different depths. This data are processed by mathematic algorithms that generate resistivity-depth graphics than can be read both vertically and horizontally.
Same as topography, it consists of gathering data from seabed or river bed to generate 3D maps that could make the decision-making process easier.
The combination of the sounding line placed in a ship and the double GPS system (one in the ship and the other one on the beach) let technicians register XYZ coordinates by a computer. Later on all data are processed and mapped.
The final result is a record made up with UTM coordinates and bathymetric points.
To achieve and in-depth knowledge of the subsoil, borehole campaigns for geological/geotechnical investigations are normally performed. The most demanded technique is wire-line coring sampling.
Samples are studied by geologists afterwards and even analysed in laboratories if required.
Measuring soils thermal resistivity is crucial to know how heat exchanges through the subsoil work and how to design them.
Data collection can be performed either on site or in laboratories, being the latter the most recommended since it let elaborate dry-out curves that help technicians map the subsoil.
Hydrogeological studies are based on the analysis of the hydric characteristics of the subsoil in order to know:
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