Methodologies
Seismic waves (P-waves) energy is generated using an acoustic source at predetermined locations (S). The travel times of acoustic energy that has been critically refracted at horizons of interest (L1) is recorded at predetermined receiver locations (R1, R2, etc.). The recorded travel time information is used to generate a velocity–structure profile of the subsurface along the length of the refraction profile.
Modified from “Introduction to Geotechnical Geophysics – N. Anderson and N. Croxton, Circular – Number E-C130, October 2008”.
SRT (P-waves) can be carried out in a variety of terrains and will suit multiple purpose.
12, 24 or 48 geophones are placed on the ground using 75mm tapered spikes to ensure good coupling with the surface. The geophones are spaced based on the required depth and resolution of the investigation and connected via a seismic cable to a seismograph.
Seismic energy source is generated along the seismic alignment and can vary based on the depth of penetration required and the terrain/environment. Types of seismic sources used by Scurbat are sledgehammer, mechanised/accelerated Seismic Weight Drop (SWD) system, “Betsy” gun and explosive charges.
Example 1: Seismic Refraction Testing (SRT) tomography section with correlation of simplified geotechnical boreholes.
Example 2: Seismic Refraction Testing (SRT) investigation to assist in the assessment of rippability based on the “Caterpillar Rippability Chart”. To facilitate the evaluation of rippability, the standard seismic velocity profile has been converted to a “traffic light” profile based on velocities specified by the client.
What are the most common uses of Seismic Refraction?
e.g., voids/cavity, boulder floaters, faulting and fault zone, dykes, palaeochannels