Cross Hole Seismic investigations are performed on soil and rock sites to measure either on-place shear velocity and compression wave velocity profiles of the soil and rock versus depth. Using these measurements, it is possible to make calculations of the dynamic soil and rock properties, for earthquake design analyses for structures, liquefaction potential studies and site development and dynamic machine foundation designs. The parameters that can be determined include Poisson’s ratios as well as shear and Young’s modules. In addition, the material damping can be determined from CH tests.
The CH method is a downhole method for the determination of material properties of soil and rock. A source capable of generating shear and compressional waves is lowered in one of the boreholes and a pair of three component geophone receivers, coupled each either, are lowered to the same depth in two additional boreholes set at evenly spaced increments (typically 10 and 20 feet from the source borehole) in a line.
The receivers are positioned on the side of the borehole casing to allow detection of the passage of shear and compressional waves, an addition the material damping can be estimated from CH test results.
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