does subsoil water have any effecy on concrete columns?

Answer 1

It indirectly affects the concrete column apart from the chemical attack on the concrete. Nimao is spot on that saturated soil has less effective stress. When soil is compacted, the friction between particles gives it strength as they are packed more closely together. As it becomes saturated, more water particles fills the gap hence reducing the friction between soil particles, thus reducing the effective stress of the soil. Thereby the less weight the soil can take from the foundation of your building before failing. How does it affect the columns? Well, your columns are sitting on a footing either a pilecap or pad footing. The friction of soil underneath this footing is going to affect how much load the support can take. If overstressed you generally would have settlement. It is not uncommon for footings to overturn thereby breaking the connection between columns and footings. And when one footing settles, more load is distributed to nearby colum/footing combination which in turn overstresses other footings nearby. Direct effect on column, not really but consequential probably.

Answer 2

when the ground water level is high, the water content of the foundation soil is higher, which means that the effective stress (the stress carried by the soil skeleton) is lower than that of an unsaturated or partially saturated soil. this, in the first run will not have any considerable effect on the column, but, after time, a secondary consolidation will occur, (the water will escape through the voids as a result of the applied stress and the foundation will settle), lowering the doundation and causing cracks in the structure or even failure of the column.
Also, concrete is pretty sensitive to chemicals like phosphate, chloride, carbon-dioxide etc., if the subwater layer has such contents, then they will react with the potential elements in the concrete (alkaline aggregates, pozzolone admixtures etc.) and have significant effects on the structural performance and appearance of the concrete.

Answer 3

Effect? My experience with concrete is that concrete submerged in water, is stronger than concrete than is not. (We did strength tests for 1 inch diameter concrete samples in a class I took.) A flow of subsoil water my move the support material away from the concrete column, causing it to drop or move. Chemicals in the water (naturally acidic) may decompose the concrete over time.

Answer 4

Yes, underground water can reduce the bearing capacity of the soil (and columns) and undermine the foundation (and columns).