Soil Density/load-bearing And "newton Meters"...

[kloghead]

This is more a question regarding soil density and load-bearing capacity than about concrete. I've already looked through the forums and searched also but found no help.

Here's my situation: I'm in Thailand and preparing to build a ~120mt2 elevated 2 bedroom home. The soil where I intend to locate the foundation is soft and silty--at least as far as the 1.5 meters I've dug down so far. I had intended on using a conventional footing & column foundation. Yesterday I met the owner of the house next door. He recommended I drill holes and install preformed concrete piles instead of footings/columns. He had his soil tested and said it was "14 Newton Meters (Nm)" and I'm not familiar with this term. A conversion calculator equates 14 Newton meters to 1.43 kilograms-force meter (Kgf*m)and 10.3 pound-force foot (lbf*ft).

So my question...is anyone able to comment on whether soil of this density is better suited to a standard footing/column foundation or should I consider the pre-drilled hole and pile installation method? Thanks

[Jackrabbit]

Absolutely use pilings, either precast of poured in place (with rebar).

"Newton meters" does not represent the soil bearing capacity. Your neighbor's number of 14 Nm is obviously incorrect and meaningless.

The usual values are in kilo-Newtons per square meter (Pascals) and would probably be something like 75 kN/m^2 (or less) if you have soft clay and silt. (That would be 75,000 Newtons per square meter or 1566 pounds per square foot.)

In any event, not using pilings would be asking for big problems.

[gregb]

Actually newton meters are joules, a unit of energy. Not sure what this means. Maybe a new found green energy source? Obviously not very efficient one though. A 1 mAh Li-ion battery would provide similar energy. That would be something about the size of a couple of grains of sand.

In all seriousness though, I would investigate a raft foundation, also called slab on grade foundation, in this case. Might have to search a while to find a qualified contractor, but if you are really worried this will give you something very solid. It will cost more though. Foundations such as these can weigh several hundred tons. There is alot of concrete and rebar involved.

Don't know what your budget is, but I would suggest alot more investigation is the order of the day before you trust the owner of the house next door who is recommending construction foundations based on electrical charges.

Edited February 7, 2010 by gregb

[trogers]

Digging down to only 1.5m will not tell you much. Neither is the suggestion you use piles, driven or bored.

What you need to find out is the depth of the first sand layer that will bear the weight of your (single elevated or double storey) house. This will determine the appropriate length of piles.

Number and size of piles depends on the spans between columns, the wider the span, the heavier the load on each column point.

[Gonsalviz]

Depending on where he is located, pilings may not work. It was my plan to use them but was told that there were too many rocks in the ground. And this was farm land, so they must have been well under ground.