Abstract
As the method of the measurement of the crack quantity in rocks, the seismic method is the most available at present. From this point of view, the velocity through a pile of rock or glass plates was measured by the ultra-sonic pulse method under the simple conditions. Regarded such crack model is divided into a solid part and a crack part, and elastically these are element of linear spring combination, the velocity is as follows; in which Vo is the velocity through the no-crack sample and α, β are respectively the thickness ratio and the Young's modurus ratio of a crack part to a solid part. Also, α may be considered to show the relative crack quantity, hence the following expression:
The result of the experiment shows the crack effect on the velocity decreases under wet conditions, large pressure, and in soft rocks.
