difference between water table and saturated soil

[lbengineer1]

Dears,

i am a beginner in this,
we have excavated 4m of land , we have obtained clay soil with no water table signs.
i know that clay absorb water, so when calculating earth pressure on my basement walls , do i only consider saturated soil density or i must include watertable effect + effectif density.

my confusion is: if my soil is clay and expansive, when its raining, does the soil become saturated or i have a water table effect on walls?

 

[oldestguy]

For basement walls usually there are local building codes that dictate some details for the foundation walls. In addition to that, you may need to consider reinforcement designed against earth pressures. These pressures can be significant, depending on many things. Normally active pressure or at-rest pressure is present and you should use the soil properties for worst case as to soil density. Then I'd use saturated unit weight (includes water) in the calculation. However, you imply that the clay is an expansive type. Under those circumstances the pressures can be far above those usual figures, even full passive pressure. Therefore, it probably would be best to consult with a local experienced geotechnical engineer for what to do. This may change your plans considerably. Expansive clays can be dealt with by a number of ways, usually not cheap. In addition the mode of backfilling plays a significant role in what pressures occur. Compaction can apply pressures well into the passive category.