Swell Vs Heave 5

[pelelo]

Engineers,

Can anyone explain the differences between Swale and Heave?.

They both occur on expansive soils and both are quantifiable, such as, a clay may have 0.1 ft of heave or 0.1 ft of swell.

Authors talk more about heave when dealing with excavations. That's something I have noticed. But again, I don't see the difference.

There is a swell factor which is expressed in %. On the other hand there is no heave factor.

Please let me know. Thanks.

 

[EireChch]

I am not sure if there is any real difference and they probably are interchangeable.

Personally I think swelling generally refers to increase in volume due to absorption of water.

Where as heave would refer to volume increase due to reduction of overburden stress. More applicable to deep basements in over consolidated clays.

 

[Mad Mike]

Agree with EireChch- I've always taken "heave" to be a stress response to a net change in pressure, resulting from excavation of over-consolidated clays or stress relief following over-compaction...swelling I've always taken to be driven by moisture changes entirely...of course there is often considerable overlap between the two.

In South Africa, the housing departments use "heave" as an all-encompassing term for expansive clays, regardless of the mechanism.

I've never seen the terms clearly defined.

All the best,
Mike

 

[fattdad]

Never thought of this, but. . .

Swell is a pressure. Heave is a response.

That's my instinct.

f-d

ípapß gordo ainÆt no madre flaca!

 

[pelelo]

Thanks for your responses.

After more than 10 years in the geotech realm I realized if there are any differences between these terms.

fattdad: when you say swell is a pressure, I agree, from lab tests you can get the swell pressure. However, you can have a swell results (e.g 5 inch swell in a fat clay). On other note, there is no "heave pressure" but you can get heave results (such as 10 inch heave).

After reading a bit more last night, there are additional terminologies:

Swell Percentage
Swell factor
Swell Pressure

The first 2 are completely different, according to the 200 solved problems in geotechnical engineering (by Affi). Swell pressure you get it from the lab tests. And Swell terminology I think refers to just how much the soil expanded (e.g 3 inches).

 

[fattdad]

. . . let's not forget about, "Heave!"

f-d

ípapß gordo ainÆt no madre flaca!

 

[L0k]

Agreed with the above comments as my understanding are:
Heave is happening due to the external loading, say you place an embankment you will get an amount of heaving.
Swell is happening due to the inner substances influencing the soil grain behaviour especially in OCC soils.

 

[pelelo]

On other note,

In the swell index test, which is used to obtain the swell index (obviously), is used to compute the amount of heave. Robert Day in his Foundation Engineering Handbook provides information about this approach.

 

[Ron]

Tomato/Tomahto....the result is the same....soil movement.

Both can happen and both can be reversed. The mechanism of cause can be different (frost, overburden, material properties, etc.)