The specific weight of dry
ash
can vary from 400 to 700 kg/m3, and rainwater can
increase this by 50-100% or more if the
ash
becomes saturated by rain, sometimes reaching more than 2,000
kg/m3. The problems of loading by
ash
are similar to those from loading by snow, but the effects of ash
accumulation are much more severe—the load due to ash is
typically much greater (see table below), ash doesn't melt, and the
ash can clog gutters and cause them to collapse, especially after
rainfall. In areas that have snow-loading codes, some protection
against ash may result but his is highly dependent on the location
of structures because snow load levels vary with altitude and
location.
Density & load comparison, 100 mm (4 in) of snow and
100 mm (4 in) volcanic ash
(Johnston, 1997; p. 75)
| New snow |
50-70 |
0.05-0.07 |
| Damp new snow |
100-200 |
0.1-0.2 |
| Settled snow |
200-300 |
0.2-0.3 |
|
Dry uncompacted
ash
|
500-1,300 |
0.5-1.3 |
|
Wet compacted
ash
|
1,000-2,000 |
1.0-2.0 |
The load on a bulding is given by the equation:
|
|