High water table 1

[aladdin76]

I have parking area under construction, the water table is high, about 1 m deep , the compacting machines sinking about 25 cm when operated in the area , and the water is going to the surface ,, any advice,,

 

[Ron]

Use perimeter ditching and drop the water table if you can. With the water table at 1m, you must have some water retaining soils at the compaction level. You might consider discing the soils to aerate and dry. If pumping is occurring, then this is likely your better option.

You don't mention the type of compaction equipment, but don't use rubber-tire equipment and don't use vibratory. Use steel wheel static compaction for this condition. If clayey soils, use static sheepsfoot compactor. In either case, use more passes with lighter compactor.

 

[SirAl]

Pretty serious rutting. What are the soils you are dealing with?

 

[oldestguy]

In these types of conditions and for a parking lot (not highly important to get 95 percent) where a stable condition is needed and no significant ruts before placing base course, I have changed the plan and use a coarse quarry rock fill, what we call "breaker run". This works well over unstable areas as the only fill.

Sometimes it is possible to stabilize the situation using rock fill that we call 3" clear, the same stuff as breaker run, but with no fines below the 3 inch size. In this case this is placed over the unstable area and compacted into the lower mushy material and the fines are driven into the voids of this rocky fill. With enough of the rock, things stabilize since all loads are carried rock to rock.

When it comes to design, however, I consider any stabilizing layer as just subgrade, not base course material.

There are other treatments that may be considered, such as stabilizing with lime or old cement.

 

[Drumchaser]

I would place underdrain (some call it french drain) complete with aggr bedding,perf pipe, then encompass the perf pipe with the same aggr.

Run these drains into a solid pipe then lay the solid pipe into a drainage structure (inlet) outfall etc.

Then I would begin with subgrade treatment, base, and surface layers.

Vibratory equipment is only bring the water to the top I would suspect.


........or you could raise the elev. of your parking area(s)

 

[oldestguy]

Another item here is my general spec that the completed subgrade should not developer ruts under truck traffic of over 2 inches. Otherwise when base course is placed there will also be ruts in that material and finally the thickness of base will be thick where there had been ruts and thin beside that area.

So, for placing base over a weak subgrade (assuming you have to and the schedule won't permit delays), I call for undercut at all storm inlets, and other grade fixing details. In the rest of the area I play with grades with a thicker than standard base course. The thickness of undercut as well as final base course is determined in the next step shown here.

This is determined by placing a test area tapered thickness of base course over a typical unstable subgrade area. Thickness varies from the design thickness to maybe twice that thickness.

Then drive fully loaded trucks over the tapered thickness test area. Where you find no "significant" ruts develop in the base surface, then chose a base course thickness somewhat above that and go with it on the job.

Adjust grades and slopes accordingly.

This tapered test area procedure also can be used to find the thickness of 3" clear or other treatment needed for upgrading the subgrade you are trying to fix.

I've used this procedure a lot and find it is accepted by owners especially when time is critical.