土建专业毕业设计外文翻译----地下水
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1、外文资料 The Ground-water The ources of water which supply water front below the earths surface are called sub-surface sources or ground-water source.Groundwater storage is considerably in excess of all artificial and nature surface storage in the United States.Groundwater distribution may be generally
2、categorize into zones of aeration and asterisked. The saturated zone ia one in which all the voids are filled with water under hydrostatic pressure.The aeration zone in whiche the interstices are filled partly with air and partly with waters, may be subdivided into three subsonic. The soil-water zon
3、e begins at the ground surface and extends downward through the major root zone of fire. Its total depth is variable and dependent on soil type and vegetation.The zone is unsaturated except during period of heavy infiltration.Threecategorise of water calssification may be encountered in this regiona
4、l: hygroscopic water content, which is adsorbed from the air separation; capillary water rat, whiche is held by suifacetension;and gravitational waters, which is excess soil water draining through the soiled. The intermediate zone extends from the bottom of the soil-water zone to the top of the capi
5、llary fringe and may vary from nonexistence to several huntween the near-ground suiface region and the near-water-water table region through which infiltrating waters must passed. The capillary zone extends from the water table to a height determined by zone thickness ia a function of soil texture a
6、nd may vary not ongly from region to region but also within a local area network. The water that can be drained from a soil by gravity is known as the specific yielding. It is expressed as the ratio of the volume of water that can be drained by gravity to the gross volume of the soil.Values of speci
7、fic yield are dependent on soil particle size average, shape and distribution of pore, and degree of completion of the soiled. Average values of specific yield for alluvial aquifers range frome 10% to 20%. An aquifer is a water-bearing stratum or formation capble of transmitting water in quantities
8、sufficient to permit development.Aquifers may be considered as falling into two categorise,confined and unconfined,depending on whether or not a water table or free within an aquifer is change whenever water is recharged to or discharged from an aquifer.Forsaturated,confinedaquifer,pressure changes
9、produce only slight changs in storage volume.In this cases, the weight of the overburden is supposed partly by hydrostatic pressure and pattly by the soild material in the aquifer.When the hydrostatic pressure in a confined aquifer is reduced by pumping or other means,the load on the aquifer increas
10、e, causing its compressional, with the result that some water is forced from its. Decreasing the hydrostatic pressure also causes a small expansione, which in turn produces an additional release of water.For confined aquifer, the water yield is expressed in terms of a storage coefficient Scarcely. T
11、his strong coefficient may be defined as the volume of water that an aquifer takes in or relleases per unit surface area of aquifer per unit change in head normal to the surface.In addition to water-bearing strata exhibiting satisfactory rates of yield,there are also non-water-bearing and impermeabl
12、e strata.Anaquiclude is an impermeable stratum that may contain large quantities of water but whose transmission rates are ot high enough to permit effective development.Anaquifuge is a formation that is impermeable and devoid of waters. Any circumstance that alters the pressure imposed on undergrou
13、nd water will also cause a variation in the groundwater level.Seasonalfactorshare, change in stream and river stages,evapotranspiration,atmospheric pressure change, windsor, ides, external load,various forms of withdrawal and recharge,and earthquakes all may produce fluctuations in the level of the
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