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Name:   
Heading: 1.1.1.1Soil-cement base layer
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Hi friends,
Does anybody know about one relationship between fine sandy soil-cement compressive strength and the elastic modulus? I need a simple formula to compute the soil-cement base layer modulus because I am interesting in modelling an already constructed two layers pavement structure who is performing longitudinal top-down cracking along wheel paths, 90 days it was finished. I suspect it was used to much cement, the base became too stiff and the sub base and clayey soil are too soft. The idea I have is compute the tension stresses the base layer is performing on top using Bisar 3 program, and compare with some allowable stress.
Any help or idea coming from your experience will be welcome.
Thanks.



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Pablo del Aguila


Pablo,

I'm not sure what your end goal is with the analysis, but as I'm not a modelling man myself I would have taken a different approach: Would it not be easier to do a simple DCP or in-situ soil test to determine the actual capacities (CBR's) of the subbase and subgrade? If the cracking coincides with deformation/ differential settlement or movement you probably have a substandard substructure - specially if it only happened after 90 days. By comparing actual to design capacities you should be able to prove the point. I'm not sure that you could define the top layer as being "too stiff", as the envelopes for the E-values in the models take into account that eventual cracking causes the cemtised base to act in a more "granular" way after crack initiation?
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Anton van Staden


Anton,
Why the top-down cracking appears? Because of the tensile stresses. So, all I want to do is to compute those stresses. Everything you say is done, but I want to go from the inference to the direct factor causing the failure for establishing a relationship between modular ratio and performance, following the Dormon and Metcalf theory. So, at this time all I need is a reliable formula in order to compute the fine sandy soil-cement base elastic modulus using compressive strength because is the only data I have.
Many thanks for your answer.
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Pablo del Aguila


Just signed up so this response is probably to late for Pablo but might help others.

The key to having a crack free soil stabilized subbase and/or a full base for direct finish paving in all soil types (clay, silt, sand or any combination) is indeed to have a high tensile strength that can overcome the brittleness of straight cement on soil stabilization. For the past 2 years I've had incredible results with a process and specialty additive that we developed here in Western Canada. Our process and soil cement mix designs achieve high compressive strength for load bearing plus increase tensile strength by up to 1800% in sand for example.

If anyone's interested post a request and I'll provide more details.
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George Clark
 
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