Site specific ground problems?

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  Available techniques for detection of old mine workings

Cross-Panel velocity and/or attenuation tomography (X-Panel^TM) generates images of anomalies in seismic velocity or attenuation within the volume of surveyed ground using travel times or power loss of seismic waves that travel between pairs of boreholes (panels), or between boreholes and an accessible and sufficiently competent surface of the ground. The technique closely resembles the medical CAT scan. The pattern of boreholes determines if the images are two-dimensional (the fence profile) or three-dimensional : typically when the panels intersect within the imaged volume.

After all survey parameters are introduced and verified, the image is generated in less than two hours dependent on the number of panels and required resolution.

C-TG continues using magnetostrictive actuator driven by a swept frequency signal as very repeatable and reliable seismic source. This approach allows transmitting controlled broad-band seismic waves into the ground by significantly reducing loss of seismic energy in higher frequency range due to plastic deformation of the ground. In turn, broad-band seismic waves provide significant improvement in resolution for both TRT^TM and X-Panel^TM techniques. This effect is particularly important for imaging piles as part of bridge abutment and pier foundations to assess their type, depth, patterns, and overall conditions.

C-TG also relies mainly on using accelerometers and pressure sensitive hydrophones for detection of seismic signals. Sensitivity of these two types of transducers is proportional to the second power of the frequency of seismic vibrations. This type of response provides the most effective compensation for frequency related exponential attenuation of seismic waves in the ground.

TomoView^TM is a stand-alone graphic engine software that has capabilities for data input, survey coordinate verification, imaging local geology and site conditions, adding comments, and enhancing analysis of processed ground images for TRT^TM in tunnels, X-Panel^TM for cross-hole site investigations, CSL^TM for drilled shafts, and SHPS-TRT^TM for pier testing. It also allows exporting 3D files to AutoCAD.