题目内容
水利工程施工中，洞井石方开挖一般可以分为：平洞石方开挖、竖井石方开挖、斜井石方开挖。
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当石渣运输为非整数时，取接近整数计算
斜井石方开挖工程是指水平夹角为45°~75°的井挖工程
地下厂房石方开挖工程是指地下厂房或窑洞式厂房的开挖工程。
Water is life. We depend on it to keep us and the 1 healthy. Nonetheless, many people take water as a natural resource for granted. Today, the situation has changed. As the population of the world increases, and with it the demand for water, there is growing concern that our water supplies will not be as 2 as we think. Eighty countries now have water shortages and 2 billion people lack access to clean water. One billion people lack enough water to simply meet their basic needs.While nearly 70 percent of the world is covered by water, only 2.5 percent of it is fresh. This tiny amount of fresh water available on the planet has remained fairly constant over time and is 3 unevenly around the world. The growth of the world population, therefore, 4 competition for a clean supply of water every year. Worse still, humans are not efficient users. According to the United Nations, water use has grown at more than twice the 5 of population increase in the last century. The reality is that an increasing number of regions are 6 with water scarcity. By 2025, two-thirds of the world's population may face water shortages.An adequate and 7 water supply is essential to the future of every country. To increase and conserve supplies of fresh water, many countries have been working at technological 8 , one of which is in the process of desalination. New filtration systems have been developed to 9 traditional heating methods. Thus the expected 10 can be achieved: lower costs.
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