Behavior of Lime-based Subsoil Improvement

[KptnNemo]

Hallo Everybody!
I wonder, if anybody has got experience with the behavior of lime-soil-mixed (1:5) soil exchange.
I´ve been faced with the problem to accept or disagree to build heavy industrial equipment foundation (including plant main building) onto already prepared strata. According to the geologist report, the soil-improvement has been properly built in and compacted layer by layer on varying level of cleaned bedrock, its thicknees varies between 0.5 to 5 m.
My concern is the following:
The existing groundwater level is somewhere at - 3.0 m.
The laboratory report says, that it dont react and does not swell also, when it gets in contact or will be saturated with water.
I have not a clou, how this good compacted lime-sand-mix will react, when it is saturated by groundwater and foundation with high DYNAMIC-Load will be placed onto it. How about the possibility of THIXOTROPICITY ?
Anybody there, who could give advise or hint to existing investigations / reports on such problems?
Thanks and regards
KptnNemo

 

[fattdad]

run some dilatometer probes and look at the soil properties in the improved soil stratum. I would not consider the presence of the water table to be anything more than it is (i.e., consider it in your dynamic design irrespective of whether it's lime stabilized fill or not. The bigger issue is whether the contractor acheived the required measure of compaction and whether the fill is a uniform engineered material. A dilatometer will help you with this evaluation.

f-d

 

[KptnNemo]

Thank you very much Fattdad for your reply!
I´ll try to find out more about your recommended dilatometer probes. I have the impression, that´s the same, what the subsoil expert did already. Borings nad SPT´s were taken, also plate bearing test were carried out, they all are showing fairly good values but they dont give any answer to my concern regarding thixotropicity of lime-stabilized soil under water and under the influence of dynamic load.
Regards
KptnNemo

 

[rconner]

I don't have any knowledge of this subject, but you may be interested (as I was when I saw same some time ago) in some of the purportedly ancient knowledge/behaviors of lime and working with same at the site

http://oikos.com/library/naturalbuilding/lime.html.

 

[LCruiser]

Whenever one considers using lime, one must consider whether or not sulfur is present. If present in the groundwater, it can continually migrate as it's taken up. Sulfur and Lime together produce heaving.

 

[irasamm]

Run some ASTM D 1196, static plate load tests on the subgrade and see if the results suit your applicaiton. Suggest multiple tests to get data on various depths of fill. If subsurface water levels vary seasonally, perform testing when the levels are highest. Install settlement markers. Have the company that 'properly' performed this stabilization to produce a warantee based on your maximum total and differential settlement values.

 

[theCorkster]

Kptnnemo:

Lime stabalization for structural improvement of soil properties should involve a design process to assess how the soil will react with a given type of lime such that the lime reaction doesn't reverse or that there is something present in the soil that would cause an adverse reaction (such as swelling). The geologist involved with the site grading should have this design report available. If there is no report, then the lime was used to simply dry soils uses for the fill construction. To me this is counter-intuitive, since you said they performed dilatometer tests on the completed fill. Why do these tests if they were only drying the soil?

The process that the contractor used to distribute and mix the lime is important as well. Specialized mixing equipment (rotomixer?) that mixes the water, lime and soil together is the best way to get a relatively homogeneous mixture. While it is possible to use graders and tractors and disks to mix the soil and lime, the mixing achieved by such an operation needs to be evaluated. If the mixing leaves concentrated lime in the soil, it will swell when water gets to it post construction.

Finally, I would go to the geologist/firm that provided testing and inspection services, and request from them the geotechnical design parameters you will need for your design. Since the observed the process, they should be happy to do this for you. This should be especially the case since they apparently performed dilatometer tests, etc. This information should get you closer to a good decision.

Good luck!