Building on sand

When I was working with a rigger at the Wilmington NC port I had concieved of buying an old Passenger Liner and turning it in to Hotel on the beach.

My rigger friend, employer, said the way to stablize the sand was to pound steel beams into the sand with a pile driver.

-From what I understand of the CR4 rules, communications are with spec site addresses and not personal addresses.

This is a great place to participate in some thought projects that I myself would be crushed to get kicked off of, or banned from, more than my neighborhood bar.

Thank you for the information and the advice about the site.

It is the first time i have used the site, so do not know all the rules yet!

Normally we would do a test drill to find out how deep we need to reach bedrock if at all possible. After that was determined we would decide whether to use steel or wood. In areas where water or salt was a factor we would use wood pilings driven down to bedrock, if possible, sometimes three in a pair for one footing. Once the footing is poured we would place weights on the base to determine settling. If all passed we would start construction. Many things to consider would be what is being held up? What will be stored or driven over it? How heavy would the standard load be? Will I possibly be altering any of these in the future?

Good Luck! Hope others can add to this or direct you to a proper site for references.

Here's another thought for residential or low rise commercial buildings built on crap soil conditions - not well confirmed but: I made a flexible concrete and the idea is that for your pour a thick pad about 24"thick. It acts like a mat. Then you pour a reinforced concrete slab on to of that. Jack it up off the flexible slab. Put in some blocks. remove the jacks. Check on the settling and jack and add shims. Eventually I believe you will have a settle point where you won't have to shim but every couple of years.

In some states (maybe all ???) well drillers are required to file thier logs. I have used these logs in the past to get sub-grade and geological information. The main problem with these logs in consistency in terminology. One man's sandstone bedrock is another man's densley packed sand.

But they can give you a fair idea of what can be encountered.

Another good source is the local college with a geology department. Many a times a professor or grad student their has mapped the sub-grade and bedrock conditions.

If bedrock is shallow, you can probe for it.

The trick with sand is to confine it so that horizonal movement is not permitted. Deep sand is generally not an issue. You may have to provide something like a sonna tube to maintain the integrity of the foundation while preparing to cast concrete foundations. For mid-depth foundations, sheet piling, injection grouting, minipiles, etc. can be used. For very shallow foundations, tensar grids, geo-cellular mats, are an inexpensive alternative.

I think you could find plenty of case studies associated with a product that is suitable for the type of foundation you are considering. I am going to assume the because you are an architect student that you are looking a building foundation.

Hi,

When you say deep sand is not an issue, how deep are we talking? Is 3m deep?

Basically I want to build on a beach, just back from the beach, but still sand. Under the sand are river boulders mixed with sand, some a large. Fresh water is at a depth of about 4m tops here.

How do you recommend we move forwards? What is THE first thing to do?

Thank you for any answers. I am obviously new here, so be gentle.

You should have a geotechnical engineer do some CPTs and determine the depth to a good end-bearing strata, or the depth and number of piles for sufficient skin friction. You can use driven concrete pile or cast in place as these are more typical, in some places steel beams have been used, as well as, wood. You can also modify soils with injection, densification, replacement, or combination thereof. As far as information regarding building on sand look at any geotechnical/foundations engineering text book half of all the content is on building on sand. Your state geologist or the USGS may have geologic maps and cross-sections that indicate the approximate depth of strata, but thses are typically done on scales of miles so not necessarily accurate for site specific use. In the end you need a geotechnical engineer to drill the site, determine stratigraphy, and analyze the soil data.

Hello,

I would like to build a 6 unit condo development. It will be built on the beach in Southern Mexico. We get small earthquake issues, but nothing major as yet.

The condos will be two level. The whole structure will be 21m (64 ft approx) wide x 12m (36ft approx).

The sand is fine with river boulders/stones underneath, some large.

Apart from building in Mexico jokes, what issues need to be addressed here?

Thank you for any input.

I'm currently in the process of designing a beach house that will hopefully be sited on a sand dune. I came across a system called Mega Anchor which is suitable for light weight construction, although perhaps not for multi storey. Anyway look the system up if you think it may help.