Mercury porosimetry has been widely used to study the pore structures
of coals. One of the difficulties in using this approach for character
izing pore size distributions involves the 'correction' of the apparen
t intrusion volumes for coal compressibility. This paper presents resu
lts which use the mercury porosimetry technique to draw conclusions co
ncerning the elastic properties of coals. Both dry and moist coals and
lignites are observed to have apparent compressibilites between about
2.6 and 8.5 GPa, typical of glassy solids. Hysteresis behaviour is ob
served on repeated compression-decompression cycles and suggests that
coal behaves like a macromolecular material under dynamic stressing co
nditions. This means that the compressibility is an apparent quantity,
and depends on the method used to obtain it. The magnitude of the obs
erved hysteresis effect also suggests that the coal dissipates a large
fraction of the mechanical energy input during compression. It is bel
ieved that most of the dissipation results from frictional processes a
ssociated with the steric difficulty of reorganizing the network struc
ture.