Sl. Huang et al., THE TEMPERATURE EFFECT ON SWELLING OF SHALES UNDER CYCLIC WETTING ANDDRYING, International journal of rock mechanics and mining sciences & geomechanics abstracts, 32(3), 1995, pp. 227-236
Citations number
17
Categorie Soggetti
Geosciences, Interdisciplinary","Mining & Mineral Processing
Swelling rock such as shale can generate uplift force below foundation
s often resulting in structure deformation. The expansive upward force
can be reduced, however, if the rock undergoes cycles of hydration an
d dehydration. An effort was attempted to measure the changes of swell
ing potentials (i.e. pressure and strain) of shales while the samples
underwent two cycles of wetting-and-drying treatments at different tem
peratures between -10 and 23 degrees C. Two sets of twenty-five shale
samples collected from one coal mine in interior Alaska and two mines
in southwestern Pennsylvania were tested under confined and free swell
ing conditions. The maximum swelling pressure and strain developed wit
hin the shales were related to three factors: shale moisture susceptib
ility, resting temperature, and initial tempering air humidity. As a r
esult of the first cycle swelling tests, 76% of the samples failed (i.
e. cracked) in the confined test and 56% of samples similarly failed i
n the free swelling tests. Samples that did not fail were brought back
to their initial state of water saturation. The second cycle swelling
tests were next performed on those samples. This attempt allowed meas
urements of a reduction of swelling pressure and strain of the shale s
amples. Swelling pressure and strain of the samples decreased consider
ably in the second cycle of tests. The reduction in swelling potential
was likely caused by the growth of microcracks in the samples during
the first cycle of swelling test. The swelling pressure and strain mea
sured in the second cycle test were noted to have strong correlation w
ith the swelling potentials measured in the first cycle.