GRAVITY-TYPE DAMS OF UNCEMENTED MASONY were built as long as 4000 B.C. The oldes recorded masonry dam was completed in 1586 near Almanza, Spain. It was constructed on rock, using rubble masonry, and stood about 48 ft. high. Errly masonry dams utilized clay mortar; later, lime mortar was discovered and used.
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只看楼主 我来说两句Water conservancy太偏保护了。如果是水土保持部,用Department of Land and Water Conservation没问题.
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