The mean spacings for each joint type in each
weathering grade are shown in Table 6. Mean vertical
and horizontal joint spacings tend to become
progressively closer with increasing weathering grade
up to HW granite, at which point mean spacing
becomes wider. Horizontal joints are wider by about
one-third in fresh granite, and vertical joints are
wider by more than 20%. Data are sparse for dipping
joints, but the trend is the same. Dipping joints in
fresh granite are about 50% wider than in weathered
granite. The increase in spacing in HW granites
probably results from the increased difficulty in identifying
joints in the more weathered rocks because of crystal disaggregation. It is likely that these exposures
contain unidentified, relict joints. The close
spacings in MW granite were expected.
Statistically, there are no significant differences
between the mean spacings among the different
weathering grades for horizontal and dipping joints.
For vertical joints, however, there are significant
differences between fresh granite and MW granite,
fresh granite and SW granite, MW granite and HW
granite, and MW granite and CW granite. The medians
for all three joint type distributions among the
different weathering grades are significantly different.
The medians are shown in Table 7.