UNIT3EmbankmentDams

1、In general, there are two types of embankment dams: earth （earthfill dam） and rockfill（rock fill dam）. The selection is dependent upon the usable materials from the required excavation and available borrow.一般来说，土石坝有两种类型：土坝和堆石坝。坝型的选择取决于能从需要开挖的地点和可用的料场（料场 stock ground）（borrow area 取土面积; 采料场）处取得合用材料的情况

2、。It should be noted that rockfills can shade into soil fills depending upon the physical character of the rock and that no hard and fast system of classification can be made. 应当指出的是（注意），根据岩石的物理特性，堆石可以逐渐变化为填土，因而不能对土石料作出严格而固定的分类。Rocks which are soft and will easily break down under the action of excav

3、ation and placement can be classified with earthfills. Rocks which are hard and will not break down significantly are treated as rockfills. 那些软弱的和在开挖填筑时容易破碎的岩石可被归入填土类。而坚硬和不会大量破碎的的岩石，则列为堆石类。The selection and the design of an earth embankment are based upon the judgement and experience of the designer

4、 and is to a large extent of an empirical nature. The various methods of stability and seepage analysis are used mainly to confirm the engineers judgement.一座土坝的选定和设计都有赖于设计人员的判断和经验，而且在很大程度上是属于经验性的。各种稳定和渗透分析方法，主要是作为证实工程师的判断而使用的。All earth dams must have sufficient extra height known as freeboard to pre

5、vent overtopping by the pool. The freeboard must be of such height that wave action, wind setup, and earthquake effects will not result in overtopping of the dam. 所有的土坝都必须有一个足够的额外高度，称为超高，以防止水库漫顶。超高的高度必须足以在波浪作用、风浪壅高和地震影响下，不会导致坝的漫顶。The width of the earth dam top is generally controlled by the required

6、 width of fill for ease of construction using conventional equipment. In general, the top width should not be less than 30 ft.土坝的坝顶宽度一般用常规设备便于施工的填筑宽度来控制。通常，坝顶宽度应不小于30英尺。If a danger exists of an overtopping wave caused either by massive landslides in the pool or by seismic block tipping, then extra t

7、op width of erosion resistive fill will be required.如果存在着大规模塌方进入水库，或者有因地震使岩块倒落而引起波浪漫顶的危险，则需要采用抗冲刷的材料填筑更宽的坝顶高度。The alignment of an earthfill dam should be such as to minimize construction costs but such alignment should not be such as to encourage sliding or cracking of the embankment. Normally the s

8、hortest straight line across the valley will be satisfactory, but local topographic and foundation conditions may dictate otherwise. 土坝的坝轴线选定应尽量使建设费用降到最少，但是也不能因此引起坝体发生滑动或开裂。一般来说，一条横跨河谷的最短的直线，可能满足要求。但是，当地的地形和地基条件可能要求采用另外的方案。Dams located in narrow valleys often are given an alignment which is arched u

9、pstream so that deflections of the embankment under pool load will put the embankment in compression thus minimizing transverse cracking.对于峡谷的坝，常采用向上游拱出的坝轴线，以便在坝体受库水压力作用而发生变形时，能使坝体压紧，从而尽量减少其横向开裂。Three problems are generally associated with the abutments of earth dams: seepage, instability, and trans

10、verse cracking of the embankment. If the abutment consists of deposits of pervious soils it may be necessary to construct an upstream impervious blanket and downstream drainage measures to minimize and control abutment seepage.一般有三个问题与土坝坝座有关：渗透；不稳定；坝体的横向开裂。如果坝座是由透水的沉积土构成，就可能需要建造一道上游不透水的铺盖和下游排水设施，可尽量

11、减少和控制坝座内的渗透。 Where steep abutments exist, especially with sudden changes of slopes or with steep bluff, there exists a danger of transverse cracking of the embankment fills. This can be treated by excavation of the abutment to reduce the slope, especially in the impervious and transition zones. 坝座岸坡

12、很陡的地方，特别在边坡突变或有陡壁处，那里的坝体填土会产生横向裂缝的危险。这个问题可以用开挖坝座放缓边坡来处理，这样的处理在不透水区和过渡区特别需要。The transition zones, especially the upstream, should be constructed of fills which have little or no cohesion and a well-distributed gradation of soils which will promote self-healing should transverse cracking occur.过渡区，尤其是

13、在上游侧的过渡区，必须用粘着力很小或无粘着力且颗粒级配良好的土料来填筑，这种土料如发生横向裂缝时能自行愈合。It is often possible, and in some cases necessary, to construct the dam embankment in stages. Factors dictating such a procedure are: a wide valley permitting the construction of the diversion or outlet works and part of the embankment at the sam

14、e time; 土坝的分期施工往往是可能的，而且在一些情况下是必须的。要求这样施工程序的因素是：河谷宽阔，可以允许导流或泄水工程与一部分坝体同时施工；a weak foundation requiring that the embankment not be built too rapidly to prevent overstressing the foundation soils ; a wet borrow area which requires a slow construction to permit an increase in shear strength through con

15、solidation of the fill. 地基软弱，要求坝体不要过快填筑，以防止地基中产生过大的应力；料场潮湿，要求放慢施工，以使土料能通过固结作用来增加抗剪强度。In some cases it may be necessary to provide additional drainage of the foundation or fill by means of sand drain wells or by means of horizontal pervious drainage blanket.在某些情况下，可以需要增设基础排水设施或填筑排水沙井，或采用水平透水的排水铺盖。Mos

16、t soils are suitable for use for embankment construction, however, there are physical and chemical limitations, soils which contain excessive salts or other soluble materials should not be used. 大多数土料适合于坝体填筑，然而，在物理和化学性质上也有一定的局限，含有过多盐和可溶性物质的土料，不可以使用。Substantial organic content should not exist in the

17、 soils. Lignite sufficiently scattered through the fill to prevent the danger of spontaneous combustion, is not objectionable. Fat clays with high liquid limits may prove difficult to work and should be avoided.在土壤里不应存在大量的有机质成分。褐煤若能通过填筑而充分分散，无自然之虞，就不妨碍使用。而具有高度流限的肥粘土，多半难以施工，必须避免使用。The strength of the

18、 impervious and semi-impervious soils depends upon the compacted densities. These depend in turn upon the water content and weight of the compacting equipment. 不透水和半透水的土料的强度取决于压实的密度。压实密度又取决于土料的含水量和压实设备的重量。The design of the embankment is thus influenced by the water content of the borrow soils and by

19、 the practicable alternations to the water content either prior to placement of the fill or after placement but prior to rolling. 因此，料场土料的含水量和在填筑前或堆筑后而未碾压前的填土实际含水量的变化，都会影响坝体的填筑。If the natural water content is too high, then it may be reduced in borrow area by drainage, or by harrowing. If the soil i

20、s too dry it should be moistened in the borrow area either by sprinkling or by ponding and then permitted to stabilize the moisture content before use. 如果天然含水量太高，可以在料场用排水或将土料耙松的办法来减低。如果土料太干燥，则需在料场用洒水和泡水的办法把土料润湿，然后再让土料在使用以前保持稳定的含水量。The range of placement water content is generally between 2 percent d

21、ry to 2 or 3 percent wet of the standard Proter optimum water content. Pervious soils should be compacted to at least 80 percent of relative density.填筑时的含水量范围一般介于比标准普氏最优含水量低2%到高2%3%之间。透水性土料至少压实到相对密度的80%。If necessary, test fills should be constructed with variations in placement water content, lift thickness, number of roller passes and type of rollers. For cases of steep abutment, the fill must b