Seismic technique is one of the most developed geophysical techniques, providing vital information on subsurface, crucial for most of the engineering projects. PARSAN specializes in Seismic Refraction surveys, Seismic Refraction Tomography, MASW, SASW etc., routinely carried out for assessment of subsurface conditions prior to engineering projects.
The seismic refraction method is based on the measurement of the travel time of seismic waves refracted at the interfaces between layers of different velocities. The seismic energy is generates at shot point using a source (hammer, weight drop, explosive). The energy radiates from shot point, and first arrivals are detected using geophones. The first arrivals can be direct arrivals or refracted arrivals, on different geophones, depending on velocities and thickness of subsurface layers. The time-distance curve is used to determine velocities and thickness of various subsurface layers.
The velocity depends on elasticity and density of material through which the energy is travelling, and hence provides information on the material strength, and helps in classification of the material.
The seismic refraction surveys are used to determine:
* Bedrock profile, rock quality and depth
* Thickness of overburden
* Fractures and weak zones
* Topography of ground water
* Rippability assessment in mines
* Slope stability studies
* Pipeline route studies
Experts with PARSAN have extensive experience in using seismic refraction for various applications including soil-bedrock continuous profiling in pipeline routes, rippability assessment in mines, slope stability studies in mines, site assessment for power plants, site assessment for landfills etc. Company has worked on various hydropower projects in difficult terrains of Afghanistan.
PARSAN has the privilege of being the first company in India to introduce velocity gradient type results, much more realistic and accurate than typical layered models, which also are provided as additional information.