FAQs
Once you complete the injection process won’t the water simply go away?
Once a moisture seal is placed, expansive clay soils will seek a state of equilibrium and so long as there are no external sources (wind, tree roots, plumbing leak, and drainage problems) then the moisture content will not change. Highly charged ions in clay soils adsorb water and the attraction is so strong that the expansive clay will not release the water unless a stronger force of attraction is applied.
Will we have to case our piers if we use water pressure injection?
Typically not. The only time piers should have to be cased is if the water table is higher than the depth of the piers or if non-cohesive soils are encountered. This potential should be noted in your geotechnical report. The single time that we know piers had to be cased because of the water pressure injection process was a result of perched water due to an overzealous engineering firm insistence on additional passes of water injection that served little or no improvement.
How expansive are the soils in DFW?
Not all soils in DFW area are expansive. Those that are characteristically range from a potential swell average of 2”-10” and in extreme cases as much as 24”.
What other construction methods are used to negate the effects of swelling soils?
There are many options available. Typically the most expensive options are pier and beam type foundations followed by a fully suspended slab.
The second most expensive choice for soil remediation is to replace in-situ soils with select fill or base material. However, owners should be made aware that if expansive clay soils are outside the excavation area, a bathtub effect can be created. This occurs when water is allowed to infiltrate the low PI soils and settle down on top of the expansive clay creating deep seated swell. Moisture conditioning by excavation and recompaction is the next cheapest solution followed by the most economical option which is water pressure injection.
How messy will the pad be after WPI?
While the pressure injection process does generate a lot of surface mud, typically it can be dried out within a few days, weather permitting. Jowell offers drying services so please feel free to contact us for more information.
Why do you not turn off the water supply to the machine when you move forward between injection points?
We leave the water supply on to clear the rods of soil and to prevent the rods from getting clogged when we reinsert them into the ground.
Do you include the cost of water?
Typically yes, so long as the job is within an hour to an hour half drive time from our office. If the owner wishes to supply the water we can deduct it from our proposal.
What if the moisture content of my building’s subgrade is already high enough so that very little swell potential is left?
If there is no potential swell left, then you’re geotechnical engineer will likely recommend that you build on the soil as is.
