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Shanghai, Pudong

Shanghai Pudong 上海浦东

Pudong District from the Jin Mao Tower looking toward Century Park and the science museum in the distance. The Wiki map coordinates are 31°13'0.86"N 121°32'28.58"E.

Over 3,000 skyscrapers having more than 24 floors have been built since 1990. Another 3,000 are planned. The problem is that Pudong is a sponge. It is an island created by the accumulation of silt at the mouth of the Yangtse River. When you place weight on a wet sponge, the water is sqeezed out, particularly in the area of pressure.

Picture a pencil standing up in wet sand, eraser end down. Now picture a pencil twice that length standing near it. Beneath the pencils the weight compresses the grains of sand and water is pushed to the sides. With sand, the grains are independent so only the water pressure from one pencil will affect the other. If the sand is dry, the pencils will have less effect on one another but they will be less stable because the sand does not cohere.

Silt does cohere. That is part of the problem with building on it. Get rid of the sand and cut out two holes in a wet sponge, just large enough to hold up your pencils. To get them equally stable, you will have to cut out a deeper hole for the tall pencil. Place your pencils in the holes. Now picture what happens under the pencils. The sponge is compressed and water is squeezed to the sides. But now as the base is compressed it pulls attached fibres downward toward the center. The two pencils, placed near one another, will lean toward one another. Now picture a building with the equivalent of an eraser tip embedded in silt. When conditions are stable, there is no problem.

Another analogy -- you are sitting on your bed - a nice soft bed. Someone comes in and sits down beside you. It makes for a cozy situation when we are talking about intimacy, but an irritation when you are trying to read. This is why water beds went out of style!

For Shanghai, the questions are how much one building will affect another and what happens when you remove water from the silt.

China Index >> Shanghai, Bund, and Pudong >> Shanghai Pudong

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Last update: February 2007
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