GEONOR has modern and versatile geophysical investigation equipment, sometimes necessary for a proper geotechnical investigation of your project.

ELECTRICAL PROSPECTING

It is a technique based on four-electrode devices by means of which current is injected into the ground and the potential difference generated is measured. This is used to calculate the resistivity of the ground and to record its lateral and depth variations, interpreting the structure of the subsoil.

Techniques such as vertical electrical sounding (VES) are used to obtain one-dimensional resistivity and depth models.

Electrical tomography methods are also applied to provide two-dimensional profiles.

For all this, a two-channel IRIS J-R1 resistivity meter with a maximum output power of 200 W and a maximum voltage of 600 V is used.

SEISMIC SURVEY

For geotechnical purposes, high-resolution seismic or surface seismic is often used. With a not excessively powerful energy source (impact hammer blow), seismic waves are generated and recorded at a series of stations (geophones) distributed in the ground. By studying the different waveforms and their travel times, it is possible to obtain seismic images of the subsoil which are then related to geotechnical levels.

Using the refraction seismic technique, an image of the subsurface is obtained in terms of the seismic velocity field (P-waves). Its purpose is to determine the structure of the subsoil, as well as to know the situation of a hypothetical rocky substrate. It is also used for shearability studies.

With seismic tomography analysis, model variations such as low velocity layers or lateral variations are not limitations. Through an iterative inversion process, the most suitable model is obtained.

Another possibility of seismic study is by means of surface wave scattering analysis (MASW). With this method it is possible to obtain a one-dimensional model, or to generate sections of the terrain, of the distribution of S-wave velocities with depth. This type of measurement is particularly useful to know the distribution of geotechnical levels at depth even when there are intercalated “soft” layers. It is also used to obtain dynamic deformation moduli of the ground and generally for the classification of Vs30 in seismic risk studies.

With the Down-hole test it is also possible to obtain the dynamic elastic deformation moduli of the soil. In this case it is necessary to have a borehole in which a triaxial geophone is inserted.

For these studies GEONOR has a 24-channel, 24-bit seismograph, DOLANG DBS-280B.