The most common approach to firming up a muddy road is to add gravel. Although this can occasionally be effective, there is a saying in the trade that “adding a bucket of gravel to a bucket of mud just gets you a bigger bucket of mud.” There is much truth to this quip, as adding something to a muddy road often has little effect, and can sometimes make matters worse because of increased agitation of an already sticky situation.
There are times, however, that little else can be done except to add aggregate to a section of road that appears bottomless for a while in the Springtime. WHAT you add and HOW MUCH OF IT is what makes the difference between success and gooey failure. see: https://www.youtube.com/watch?time_continue=2&v=pAF4oESO504
From my years of maintaining roads and developing house lots, I’ve found that the only practical way to treat a mud hole is to add enough coarse aggregate to fill the entire hole, essentially bridging the weak spot with strong supporting material. This material needs to be extremely porous and can consist of small rocks or large, graded crushed stone (usually 1½”, not pea stone), and should contain virtually no sand or fines. The goal is to provide enough of this coarse material so that, once it’s in place, each rock or stone touches another, and the mud that was there now just fills the gap between stones. The emergency repair takes on the characteristics of the fill material rather than that of the mud it has replaced.
Using sand or gravel to fill a mud hole usually has little or no effect because the stuff ends up mixing with the mud, just making more mud and sometimes aggravating the problem as equipment stirs things up. In a similar manner, adding stone or rock aggregate in an amount insufficient to fill the mudhole and transfer wheel loads from the surface through the mud to a firm base can have little or no effect.
In some cases it is impossible to add enough stone to fill all the way from the road surface to a firm base. Clean, sharp, angular stone aggregate will knit together in an interlocking action to support substantial weight by spreading wheel loads over larger areas. This can be successful with lighter loads but lose its effectiveness when heavy trucks repeatedly push the stone into the weak soil underneath, requiring the addition of still more stone.
The disadvantage of using very much stone to stabilize a road is expense, as crushed stone is one of the most expensive types of processed aggregate. The only time I use stone for stabilization is for emergency repairs. Once frost has left the road base and the road has become workable, I use geotextile stabilization fabric with outstanding results. For new road or driveway work I try to get the fabric in place before the site gets muddy, eliminating the need for excessive stone at the start.
Geotextile fabrics can effectively eliminate muddy conditions on a road by keeping gravel surface materials from mixing into the road base as wheel loads push the road surface materials down. Geotextiles provide a modern, low cost, permanent solution and are gaining wide acceptance.
If you are building a road through an area of known weak soil condition or have a road that turns to soup each spring, plan on using a geotextile under the road surface for a permanent solution when possible. If you have a few sink holes here and there and have to make them passable during the spring, try adding stone. But be prepared to add enough to do the job completely or you can expect to end up with nothing more than just a bit more mud.