Three-dimensional Reflector Tracing system
(TRTTM) records seismic waves generated and detected by 3D 'tube array' of
sources and receivers coupled to the tunnel walls. The technique is
particularly useful for imaging ground conditions ahead and around
advancing tunnels. The technique resembles medical ultra-sound imaging.
Stacking and triangulation of recorded waves generates color-coded
anomalies at the reflector locations within the volume of surveyed ground.
These images of reflectors are considered reliable as far as 300ft/100m
from the array dependent on ground conditions. The magnitude of an anomaly
is proportional to the absolute change in seismic impedance (product of
velocity and natural density) at the reflector boundary. The blue to
purple color of the anomaly indicates ground changing from higher to lower
seismic impedance, while yellow to red indicates higher seismic impedance.
After all survey parameters are introduced, the image is generated in less
than an hour.
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 TRTTM and
X-PanelTM 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.
TomoViewTM 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 TRTTM
in tunnels, X-PanelTM for cross-hole site investigations,
CSLTM for drilled shafts, and SHPS-TRTTM for pier testing. It also allows
exporting 3D files to AutoCAD.
