SEISMIC TEST
In the seismic method, the movement of the ground resulting from an elastic impulse (originated through impacts on the ground, vibrations or explosive) originates acoustic waves that are recorded through geophones connected to a multichannel seismograph. The Seismic Refraction is based on the observation of the arrival times of the first movements of the terrain in different places, generated by a specific energy source in a specific site. The data set obtained in the acquisition of data consists of time versus distance records. These series are interpreted in terms of the depth at interfaces between soil layers and the propagation velocities of the wave Ould (or S) on each layer. These speeds are controlled by the elastic parameters that describe the material.
Applicable standard: ASTM D5777-00 Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation.
Applications:
-Stratigraphic characterization of the subsoil.
-Determination of the depth of the rocky substrate and its morphology.
-Definition thickness of an altered layer of rock.
-Definition Vs and Vp for determination of mechanical parameters.
- Geomechanical classification of the rock.
-Definition index Q and Emass.
-Definition of other geotechnical parameters such as fracture index (RQD), density (sedimentary rocks), porosity (sandstones).
-Characterization of tunnels.
-Determination of excavability (rippability).
-Definition and mapping of seismic stratification, lateral variations (faults, etc.) and vertical (contacts and change properties.
-Definition of the depth of the rocky substrate.
-Identification of cultural and geological elements in the subsoil (fillings, karsts cavities).
-Definition of elastic / dynamic and geotechnical parameters integrating seismic measurements to density values (modules of shear and dynamic deformation, volumetric and oedometric compressibility) and others such as the load potential (qa) for sediments and the RMR (rock).
-Risability.
-Reclassification of floors after remediation works.
-Definition of parameters such as Vs30, geotechnical substrate).