I'm planning a basement 3.6m depth, ~0.5m of which extended above ground surface level, in a deep clay/alluvial terrain (bedrock inaccessible). Torrential rainfall during rainy season saturates the region, causing considerable flooding in low-lying areas. The basement, while not where flooding would occur much above ground level (no more than about 20 cm./8 in.), would have no option for drainage for anything below grade. Power outages are not uncommon, especially during a strong storm, making a sump pump an unreliable option. I expect, therefore, to essentially be building an inverted pool.
To prevent water entrance, 2 or 3 mm. thick steel plates could be welded together to create a waterproof liner for the concrete walls. I had planned to use either 8" blocks, poured full, or to pour the entire wall outside the liner. But as concrete is porous, and could admit some water, I then realized the need to account for hydrostatic pressure potential, and, quite likely, would need to have the steel as exterior cladding to the wall. Sooner or later, ground penetration of the water would be inevitable, and rising water levels would create a lateral load against the basement wall. Assuming the maximum pressures (worst case scenario), what is the minimum wall strength/thickness required to maintain the wall's integrity?
- Basement cladded by steel plating for waterproofing
- Alluvial/clay soil, no bedrock
- Basement dimensions about 8m x 12m (about 26ft x 40ft) and about 3m/10ft below grade
- Heavy monsoon rains--Limited pooling of water may be expected above grade, no more than about 20 cm./8 in.
- No viable option for drainage below grade **
- Two floors are planned above the basement, with exterior walls of 8" block (very uncommon for this region, and hard to obtain--the common block size being 3").
- Would like to consider the potential for seismic activity and accompanying liquefaction.
- Steel is expensive, but concrete blocks and cement are not.
- Termites are ubiquitous and will ravage most woods in a short time; i.e. wood is not a good option.
- What are the wall requirements to withstand the worst-case hydrostatic pressures?
** I took measurements of the grade today and asked a new question HERE regarding the possibility of drainage. Perhaps there's a small chance of it.