Abstract
The propogation velocity of waves through ground has been used for many years in the seismic surveys for the detection of underlying strata. From a knowledge of the percussion (P) and shear (S) wave velocities in different materials, together with their bulk densities, it is possible to derive dynamic moduli and properties, such as the shear modulus (G) and poisson’s ratio (n), which are essential in the solution of problems relating to dynamic earth pressure, soil structure interaction and the dynamic analysis of foundation strata relating to earthquake engineering.
 The principle involved in finding the wave velocities in ground materials is the same as used in finding velocities in any material. A simple wave form or pulse is generated at one point and the travel time to several other points is detected with suitable signal receivers.
Highlights
The propogat ion velocity of waves through t h e ground hasbeenusedfor many years in seismic surveys for the detection of underlying strata
A simple wave form or pulseisgenerated at one point and the travel time to several other point s is detected with suitable signal receivers
The disadvantage pf a laboratory t e s t is that i t finds the prop erties of only a very small sample of material
Summary
The propogat ion velocity of waves through t h e ground hasbeenusedfor many years in seismic surveys for the detection of underlying strata. The disadvantage pf a laboratory t e s t is that i t finds the prop erties of only a very small sample of material This i s where the field test has a primary advantage in that i t average s out small variations in the material and provide s value s which apply to agenerallylarger body of material. Theore tically the strain can be determined from the ratio of the particlevelocity over the wave propogat ion velocity ( * ) but the tests made so f a r in developing the method de scribedbelow have not provided an absolute measure of the particlevelocity , and the strains cannot be accurately found, althoughitis known t h a t they a r e very small
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