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Geologist for soil study (south 24)


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Bonjour tous.

We are struggling to find a qualified person to do a soil study on our and our neighbours' property. (Both properties have some cracking probably caused by subsidence resulting from drying out of the soil).

We are about 25 mins S.W. of Gourdon. Any suggestins most welcome.

Thanks a lot, Chris.
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Are you sure you need a geologist?
You might be better using a structural engineer or building surveyor with experience of subsidence,the engineer can inspect the properties and at the same time inspect trial pits which need to be excavated adjacent to the buildings to expose the foundations.

The building survey will check the construction and record defects of structural significance.
These defects can be evaluated to establish whether they are as a result of an other cause rather than subsidence.
All drains should be checked as leaking drains can cause subsidence by
a; washing out of fines in granular soils or
b; softening of cohesive soils (clays)

The species and location of nearby trees should be identified and located on a site plan.Trees significantly affect the required depth of foundations in clay soils.

The trial pits excavated at the side of the building should expose the foundations and extend say 0.5m below,these are inspected and details recorded,if clay is found the strength can be checked in-situ with a hand held shear vane.Soil samples are taken away for testing,these are 'double-bagged'to prevent drying out.If trees are affecting the foundations roots are occasionaly seen in the pits.

The clay is tested for three properties
1.Moisture content
2.Liquid limit(the amount of water needed to make the clay flow)
3.The plastic limit(the amount of water below which the clay becomes non-cohesive)
The differance between the plastic limit and the liquid limit is the plasticity index,this is used to determine the depth of foundations required taking into account any adjacent trees(this varies significantly depending on the species)

Once all this information is gathered you should be presented with a report that recommends what remedial works are required.
At the worst underpinning will be required in the UK the VERY APPROXIMATE cost is 500 per linear metre.

If you need assistance with the above please do not hesitate to contact me.

Tony CEng MIStructE
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