In a message dated 12/13/00 4:12:27 PM Mountain Standard Time,
[log in to unmask] writes:
<< I'd be cautious about encouraging the use of the "super" singles or wide
singles like the Europeans use on their trailers, despite the significant
fuel advantages and the fact that you can spread the spring centres and thus
increase stability. They are harder on pavements than duals. That might not
make a big difference in Europe or even in most of the US, given the
thickness of their pavements etc but in Australia where we have thin
pavements and in Canada where the base turns to pus when it thaws in the
spring I wouldn't be encouraging the things. >>
As a former District Engineer for the Asphalt Institute, I would also urge
caution with the super singles. It is a matter of pavement thickness, and
also of excessive material stresses created by high loading (in pounds per
square inch) at the pavement/tire interface.
If you would recall, pavement thickness design is based on ESAL's. Witzak
and Yoder demonstrated a 4th power relationship for increasing single axle
loads in relation to pavement deterioration. Tandem axles greatly reduce the
pavement deterioration. There may be good models for the impacts of super
singles -- I am not aware of them -- but I am inclined to think that they
would cause much more rapid deterioration of the pavement than most tire
configurations. Therefore, caution is warranted -- and I would want the
manufacturers to provide me some data before I would risk tearing up the road.
I would think that increasing the footprint of the tires would provide more
traction on a sandy road, so the concept of lowering the tire pressure might
work.
Another strategy would be to increase the ability of the roadway surface to
accept the tires "as is". There are plenty of publications on gravel road
maintenance, but I would recommend one by the US Army Corp of Engineers.
Blading the road and mixing in a high float emulsion may be of interest to
you. I have seen plenty of roads stabilized used calcium chloride, mag
chloride, and other substances, but the HFE seems to work best -- especially
when followed up with a double chip seal.
Good Luck!
Stephen Mueller, PE
Denver, Colorado, USA
|