TEST TO DETERMINATE COLLAPSE POTENTIAL

[COLLAPSIBLESOILSMAN]

How can I meassure the collapse potential of a soil?<br>
Do you have information about th collapsible soils characteristics?<br>
Thanks and Best regards

 

[georam]

The collapsing behaviour of this type of soil generally occurs when the water is introduced into the soil. Technically, the collapsible soil obtains some of its strength from cemented/bonding between the soil particles. In the arid region/Middle east, the aeolian sand (which was loosely placed), and upon some cementation process may become a collapsible soil (high strength when it is dry). Some cracking of buildings in this region, however, may be attributed to the introduction of water/moisture after the building is occupied.... ie. settlement of the soil after water is introduced (via gardening, drainage, cooking water, bath, sewer line, septic bed, etc).<br>
<br>
To measure the collapsing potential of this type of soil, you may use an oedometer/consolidation ring to prepare an undisturbed sample (similar preparation as consolidation test). When water is introduced to this specimen, the sample may start to collapse, ie. change in height... dh/h or change in initial void ratio e/eo may be used as the degree of collapse of the soil. This is like a reverse test to determine swelling potential of soils.<br>
<br>
hope that this helps. <br>
<br>

 

[dirtman]

There is an ASTM Standard Test method for this evaluation. Refer to Volume 4.08 or 4.09. Also, see the Bureau of Reclamation book Design of Small Dams. It has a chart relating the ratio of insitu dry density to the Standard Proctor dry density and the difference between optimum water content to insitu water content to collapsibility. Collapsible soils are often mud flow alluvial fan or windblown silty clays. They are characterized by a visible porosity, a low dry density and low natural water contentt.

Danny McCook

 

[KAM_imported]

In addition to what the others have said, you can recognize collapsible soils from their low density, their geologic deposition, and using lab compression tests. If the water content of the soil at saturation exceeds the liquid limit, the soil will collapse if it gets saturated. The main goal should be keeping water out of these soils (keep them dry). Design should include sloping the ground surface away from the structure, using foundation drains, extending downspouts at least 10 feet away from foundations, making sure water cannot pond close to structure, being aware of automatic sprinkler systems, etc. On big projects, the ground can be made to collapse prior to construction by the addition of ponded water, followed by preloading to take out additional settlement.

 

[sugi]

Collapse potential can be termed as hydrocompression potential or hydroconsolidation potential. A open strucured soil or weakly bonded soil or soluble bonding agent may lead to the collapse on inundation or submergence of soil. Collapse is differ fron consolidation from the fact that consolidation takes long period for settement to occur while collapse occure in short duration on inundation also in collapse there is addition of water while in collapse there is expulsion of water.
Collapse do occure in all types of soils including sand, silt ,gravel or even compacted soils. Wetting induced collapse may occure in compacted soils.
Jennings and Knight (1975) had corelated collapse potential with degree of sevarity to the structure. Such as if
Collapse potential Problem
0 No problem
1-5 Moderate trouble
5-10 Sever trouble
10-20 Very danger
For determination of collapse of soils, following methods are available: i) Single Oedometer collapse test
ii) Double oedometer test
iii) Down hole test
iv) Double triaxial collapse test
v) Laboratory infiltraion test
vi) Field infiltration test
vii) Triaxial A-value corelation with collapse potentials.

 

[DirtMD]

Realizing my question is soil dependent, .....How long should the soil specimen be allowed to sit after being inudated with water, 1hr, 4hr, 24hr, or more? Is an hour of similiar dial readings adequate or have soil structures been observed that can hold together longer?

 

[Focht3]

Good question. The simple answer is, &quot;It depends.&quot;

Generally speaking, the collapse will happen within the first 24 hours. In sands and silts, it's immediate (i.e. within 30 minutes.)

But in certain heavy clays that may swell as well as collapse, you may need to wait 72 hours for a final answer.

Sample quality is key - keep in mind that even sampling with a pushed Shelby tube can result in a compressed (i.e. densified) sample. Block samples are the best, particularly in the silts and sands -



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