307
edits
Changes
沙坝
,no edit summary
[[Image:SandDamConstruction.JPG|thumb|right|200px|建造中的沙坝。索马里兰。 Eric Fewster, BushProof / Caritas]]
[[Image:CompletedSandDam.JPG|thumb|right|200px|竣工的沙坝。索马里兰。 Eric Fewster, BushProof / Caritas]]
* Timing is important: dams should be built during the dry season, but don’t build dams too close to the rains in order to avoid the trench filling up with water or the dam being washed away.时间安排很重要：建坝需在旱季进行，且勿太临近雨季，以避免沟渠被水填满或坝体被冲走。* The method depends on the type of dam and the type of ground. The construction of sand dams in cascades improves total storage and efficiency and minimizes seepage losses. Dams made of concrete, stone-masonry (cheapest and easiest) and brickwork require skilled labour for construction, but are stronger and have a longer lifespan. 建坝方式由水坝类型和地质类型来决定。在梯级地形上建造沙坝能提升总储水量和效率，并将渗流损失降至最低。建坝方式由水坝类型和地质类型来决定。在梯级地形上建造沙坝能提升总储水量和效率，并将渗漏损失降至最低。混凝土、砌石（最便宜、最简单）和砌砖建成的水坝虽然需要技术娴熟的工人来建造，但会更坚固，使用寿命也更长。建坝方法由水坝类型和地质类型来决定。在梯级地形上建造沙坝能提升总储水量和效率，并将渗流损失降至最低。混凝土、砌石（最便宜、最简单）和砌砖建成的水坝虽然需要技术娴熟的工人来建造，但会更坚固，使用寿命也更长。
* Usually sand dams are built onto a rock layer, but where there is no rock and only clay, it can still work but as long as the foundation is keyed into the clay layer and where the wall does not protrude more than 0.5m above original sand level, otherwise there is a risk the structure overturns during a flood event.通常，沙坝要建在岩层上，但在没有岩石而只有黏土的情况下，只要地基能嵌进黏土层，且坝墙不超出原有沙层0.5米，沙坝仍能运行；否则在洪水期间，坝体有倾覆的危险。
* Key into banks or construct wing walls to avoid erosion around edges of the sand dam. Where wing walls are built, a good technique is to start with the wing walls and work inwards to the centre, since community enthusiasm lags by the time wing walls are constructed (if not built first), yet they are essential to proper functioning. Length of the wing wall varies according to bank characteristic: loose riverbanks, 7 metres; hard soils, 5 metres; hard & impermeable soils or rocks, wing wall is not needed. Planting napier grass along upstream riverbanks controls erosion and fixes the course of the river in a flood.坝体需嵌入河堤，或建造翼墙来防止沙坝边缘侵蚀。建造翼墙的情况下，较好的方法是先从翼墙开始建造，然后向中心动工。如果不先建造翼墙，社群的建造热情会在翼墙竣工前就下降，而翼墙对沙坝的正常运作来说至关重要。翼墙的长度随河堤的特性而定：松散的河堤，7米；硬质的土壤，5米；不透水且硬质的土壤或岩石则不需要翼墙。在上游河堤种植象草可以控制侵蚀，并在洪水中修正河道。
<b>埃塞俄比亚的波拉纳地区：</b>
====Akvo RSR项目====