Air Permeability as Measure of Rock Mass Behavior

Abstract

The structural looseness and the permeability of rock have been found to be strongly correlated, and on-site measurement of permeability is shown to be a promising new method of detecting structural looseness of rock mass and hence the stability of nearby structures. The vacuum permeability test obtains the permeability by suction of air from a sealed test section. It has high sensitivity and fast response to a low permeable medium and is particularly suited for this purpose. The details of the method of measurement, hardware, and the data reduction methods developed so far are described. The loosening to be detected may be due to excavation of various types or to long-term deterioration of the surrounding ground due to natural processes. Practicality of the method is demonstrated by several sample field tests conducted at various sites.