三峡围堰爆破和水库蓄水不会诱发大的地质灾害 - an simplified calculation

It should be pointed out that weight of the water in the Sanxia reservoir is very small compared to the mountains beside the rivers. First, the average density of rocks to form the mountains should be at least 2 times of the water. Each of the mountains is in shape of upward triangle as a simple assumption and they are in thousand meters above the original river bed. On the other hand, the water in the reservoir is at the maximum 170 meters above the original river bed and forms or reverse triangle as simply put. The weight of mountain rocks on both sides of the water body should be significantly larger than that of the water body. Therefore, It has no reason to say that the reservoir caused the earthquakes. Taking a simple example, if the mountains beside a cross-section of the reservoir is 100 m and the average slope angle considering the hard rock in Sanxia region is 45 degrees, the water is at the maximum 145 m deep. Take the average density of mountain rock to be 2 tons per cubic meter and water is 1 ton per cubic meter. If we take a slice of 1 meter thick of the mountain and the water, the total weight of the mountain above the river bed is about 4,000,000 tons while the water is about 21,025 tons. Comparing the two, the weight of the added water due to the construction of the reservoir in the slice is only about 0.5% of that of mountain rock. If the ground is originally stable without frequent earthquake activities, there should be at least a safety factor of 2.0 or more. In other words, the earth crest located under the selected slice should be able to withstand at least 8,000,000 tons of mountain rock before causing significant deformations that might cause potential earthquake. By that sense, the construction of the reservoir in Sanxia might increase the earthquake susceptibility by a merely 0.25% to the maximum. Statisticians can tell us how remotely that possibility is.

By the way, I am not a earthquake specialist. But a simple calculation like this (middle school knowledge) can help us to tell the truth from the others.

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• 三峡围堰爆破和水库蓄水不会诱发大的地质灾害 - Correction -Happyyl- ♂ (41 bytes) () 05/12/2008 postreply 14:14:23