30
source, R waves are the typical waves measured in the wave propagation
technique.
Wave propagation theory is based upon the fact that in a homoge
neous isotropic half space subjected to an external disturbance, waves
travel at velocities that may be expressed as (59, p. 153; 79; 127)
V, £)  )/2 Eqn. 2.2a
p 2(1 + u)p
v = ( HV-J1.) )x/2 Eqn. 2>2b
P p(l + y)(l 2y)
VR = aV$ Eqn. 2.2c
where
Vs = shear wave velocity,
Vp = compression wave velocity,
Vr = Rayleigh wave velocity,
G = shear modulus,
E = Young's modulus,
y = Poisson's ratio,
p = mass density, and
a is a function of Poisson's ratio and varies from 0.875
for y = 0 to 0.995 for y = 0.5.
In general, R and S waves are not particularly dependent on Poisson's
ratio, but the value of compression wave velocity is strongly dependent
on Poisson's ratio (59,79).
Field test procedures for the wave propagation measurements involve
two general types of tests. Raleigh wave velocities are determined from