Tuesday, June 2, 2009

Earthquake

In my last blog posting, I had gotten to the part where we had found and bought our property just north of Monkey River Village. We engaged the services of Sam Scott to be our building contractor, which viewed from the post-earthquake perspective, was a brilliant decision. The May 28th earthquake did some real damage to Monkey River Village and to Placencia. Most of the damage in Monkey River Village was due to ground liquification, which allowed the support posts of many houses to sink into the ground up to 8 feet. Some support posts subsided in their entirety, leaving the houses resting flat on the ground. Concrete buildings in Monkey River Village and Placencia also suffered damage with cracks and deep fissures forming. It seems that wooden structures may have fared a little better than concrete because they can flex, give, and skew with the earth’s movements without cracking apart.

So how did the Englishtown buildings fare in the earthquake? Quite well, as it turns out. None of our buildings have structural damage! Perhaps it was all the luck of the draw, but I think we, along with Sue and Chris Harris, have Sam Scott to thank for his 3 dimensional “matrix” support system that kept our buildings from subsiding. The picture below shows how our cabana is supported 12 feet above the ground on the system Sam designed. You can see the cubic spaces defined by the vertical and horizontal concrete supports. The 20 vertical supports are spaced approximately 10 feet on center. What you can’t see is that vertical supports continue into the ground for about 3 feet and have horizontal supports connecting them, also at 3 feet below the surface. This design distributes the weight of the house out over the buried horizontal supports. The weight winds up being distributed over a total of 310 sq feet instead of just 20 sq feet if the horizontal supports were omitted from the design. This means that if a portion of the ground under the cabana becomes liquefied, the remainder of the structure can still support the cabana without anything subsiding. The matrix structure also permits the sand and any liquefied soil to move around and between the supports without producing enough force to crack them. Anyway, that was the theory as Sam explained it to us, and I believe that his theory has been born out. We have 3 buildings with this support and I think Sue and Chris also have at least 3. Now you might think that Englishtown just didn’t have the same sort of shaking that Monkey River Village and Placencia did, but pictures from Sue and Chris’s house showing much of their furniture knocked over indicates that we had a lot of shaking going on in Englishtown too. And both of our docks subsided a foot or more. So all we can say is “Thanks, Sam!”




2 comments:

  1. All's well, that ends well! Great to hear you won't need to rebuild your house from the ground up. The house we're in here in San Jose was built to revised code after the 1989 quake - so we also have a specific foundation designed to "take it." Let's hear it for those engineers working to make a shaker - survivable - it won't be your last.

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  2. Glad your place suffered no great damage. It's nice to see engineering work as it should!

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