Geophysical investigation can be used to pinpoint locations within a site without disruption caused by boreholes, trial pits, cores or breakouts. In each case, the correct geophysical techniques must be used in the proper investigation manner to yield clear results. Investigation programs should be designed and undertaken by qualified and experienced geophysical professionals, and should make full use of available instrumentation and software to provide reliable interpretation in a timely and efficient manner. TerraDol provides consultancy, investigation design and geophysical investigation services for civil construction projects. We routinely apply state of the art geophysical instrumentation to identify subsurface man-made or natural abnormal features. Our professionals have international profiles through experience in geophysical data collection and interpretation, with work ongoing into new equipment and data processing software. We possess various types of testing equipment and software and are able to provide reliable investigative services within reasonable time at a reasonable cost.
Equipment & Software list
Ground-penetrating radar (GPR) survey uses radar pulses to image the subsurface condition. GPR can be used in a variety of media such as rock, soil, ice, fresh water, pavements and structures. It can detect objects, changes in material, and voids and cracks.
Seismic Reflection and Refraction
Seismic reflection follows the law of mirror, which images the angle of reflection from a surface to equal to the angle of incidence.Seismic refraction survey is used to determine rock competence for engineering application such as depth to bedrock, groundwater exploration, crustal structure and tectonics.
Seismic tomography is a technique used for imaging subsurface characteristics to identify deep geologic structures. Measurement of ample compression wave (P-wave) and shear wave (S-wave) travel times enables to compile 3D images of subsurface velocity structures.
Electrical resistivity is a geophysical technique for imaging subsurface structures by measuring electrical resistivity at the surface or by electrodes in one or more boreholes.
MASW method is for evaluating elastic stiffness of ground by measuring shear-wave velocity (Vs), which is closely related to Young’s modulus of the ground material. The shear-wave velocity (Vs) is a direct indicator of the ground strength (stiffness) and used to derive load-bearing capacity and define rock line for underground construction projects.
The seismic crosshole test provides dynamic subsurface properties by determining wave velocities. Seismic waves are generated in a source borehole and are recorded in a receiver borehole (CHT) or at the surface (CHT). The measurements can be performed below and above the groundwater table. These tests are mainly applied for the investigation of construction sites.
Borehole televiewer logging is used to obtain oriented images of borehole cores by acoustic signal (Acoustic Televiewer) or high resolution digital image (Optical Televiewer). These methods utilize a built-in fluxgate magnetometer to orient the image with respect to magnetic north. The output data provides a unique ability to present the core either as a wrapped image, looking out from the center of the borehole. Analysis of the data allows void and joint data to be presented in terms of depth, dip direction, dip angle, and strike.