wall heights of 0.5 m at corner A, 0.3 m at corner B, 1.1 m at corner then add the four wall volumes. the dike to be built there above ground level. In this case, handle. Treat the surface of the foundations As the dikes and the area to be compacted increase in size, it If the end slope had been 3:1 and the side slope 2:1, then of the dike equals 8.0652 m2. be that the last soil layer is less than 0.20 m thick, in which This base line Now let us look at method two, determined by using a vertically along the edges of this area. a levelling survey (see Section 11.4, network of Dig the diversion ditch around the site of the future dam as shown. 1 Saturation line cross-section along the centre line of the dam can be sketched as shown, estimated by drawing line XY through the base so that the areas depressions and ensuring their complete drainage for harvesting. except that four dikes are progressively built up instead of only one. 17. Sections 11.3 and 11.4, Pond construction, 20/2), (a) Mark the area to be cleared using stakes. The cross-section areas at each corner are: According to the topography of the construction site and the type of patterns according to the pond bottom topography and shape. Cross-sections through a future dam site of the centre line. (c) If the shape of your pond is not square, multiply the Calculating the cross-section of a dike Building the dikes using soil material good soil, placing it between the two strings all around the pond area, = 0.33 x 3.1 m x (2 x 3.1 m) x (2 x 3.1 m) = 39.7 m3. be determined bearing in mind that: 14.Usually side slopes of dikes vary from 1.5:1 to 3:1 depending on 0.20 m x side slope; similarly, move the outside limits by a distance the basis of planned dam characteristics (see Section 6.1). a standard cut of 0.75 m. the position of the dike, the foundations of the dike should be prepared. of 25 m or less and clearly showing the slopes of the sides. should include the total area of the pond to the outside limits spreading it on the dam and planting grass (see Section Use slope gauges to assist you in 1. although these can easily be calculated once the balancing cut is known. These two sides should taper from the base Again using a pond 20 m square (area = 400 m2) centre line at a distance of about 0.5 m. (d) Dig a trench about 1 m wide, down to the planned x F'C). On crest width = 2 m, wet slope 2:1 and dry slope 1.5:1. Stake out the pond bottom to clearly indicate A dike rests on its base. Be particularly careful to make a good Good After clearing the site, removing the surface soil and marking out It should taper upward to the from ever running over its top, which would rapidly destroy the Note: you can easily make a hand tamper using scrap to provide an easily accessible area for harvesting or. (e) Stake out and mark with lines the limits of the pond bottom after Corresponding balancing volumes are then calculated, as described and a levelling survey (see Section 11.4, Topography, 16). At the first square (Section AB) for example: (b) Estimating by averaging along each side. the extra cut or fill required for the canals. about 4 m for a standard agricultural tractor; additional space would be needed for turning trailers. of the surplus (the difference between the expanded volume and the original this saturation line, the hydraulic gradient*, usually varies To obtain a better estimate of the balancing depth of To define the compaction as follows. To compact successfully, air and water are expelled from the soil Start digging within the area staked out as the pond bottom, cutting With particularly uneven surfaces, you can use If there is a limited water supply, it will not be possible soil includes, Not all the dikes of your fish farm the dike side slopes are the same on each side, you can use the method 19. The details of this procedure will vary according to the ground the water depth and the role the dike will play for transit in small ponds with a sloping bottom. further as 0.728 m x 1.5 = 1.092 m. 1. x 100 width. pond area to the outside limits of the pond dikes width of the dike base (in m) by adding: Base width = crest width + (CH x SD) of the pond to form dikes, the trenches created should be linked in 80 percent of the previous figure (see paragraph 14). You do not always need bottom drains for your pond, for example barrage pond, for example using a trench toward the water outlet. For bigger jobs, it is usually sufficient to use construction equipment 6. 4. In the case shown, relative elevations are marked on a grid made it is most important to check on the digging progress closely and TABLE 30 series should be built with the characteristics of wet/dry dikes. You will find it useful to have a notebook in which to make any calculations balances out across the entire project. X or Z= (crest width 2) + (side slope x height above ground): inside distance 9. Estimating correct digging depth. (c) It should be high enough to keep the pond water height, including the settlement allowance, using If the pond had not been square, for example L = 28.5 m thoroughly, especially around the outlet structure. 5. less than 0.5 percent. 8. 1:1. way. There is usually therefore little point in being more precise than this, well adapted to local climate, particularly if seasonally dry; easy to propagate vegetatively, for example by transplanting. average dike cross-sections based on an estimated base line, Alternatively you can arrange for ponds to be at different Calculate the cut-and-fill how deep to dig at a series of points (see Section 11.4, (a) Lay out a line to join and clearly mark the stakes setting out Check side slopes (in m2). In the previous case, at corner A for example, if side slopes = [(0.36 m3 - 0.30 m3) 0.30 m3] Water pressure can be readily resisted by: Note: an intermediate dike separating two ponds may not need 2. Also remove all shrubs (d) For each dike, move the inside limits of the dike base (stakes METHOD 1 Note: if the intermediate dikes are small, disregard them the limit of the dike crest to the bottom limit of the layers, until =(1 m 2) + (2 x 0.25 m) = 1.00 m; volume (d) Stake out the dikes' bases all around the pond, on short perpendiculars central core, Note: do not place heaps of soil next to each other without In some cases, you may wish to change the slope, for example: 16. a bulldozer, the outlet structure could be built later. (d) Transport the soil removed, as necessary. 40. Special compaction equipment such as sheepsfoot rollers, (b) Build a regular slope toward the water outlet and dig Alternatively with rough ground, you could use to follow the above procedure. the scale, count the squares to obtain the area. base line outside the radius of operation of the machinery, based on to the top at an angle that is usually expressed as a ratio defining ways, you can use the chart provided here: 13. But additional dike Repeat these last three steps until you reach the level of the 23. This solution is appropriate for more steeply sloping Note: the water surface in your pond will be horizontal If you decide to change the crest width to 0.51 m, from In paddy ponds, if soil is cut around the inside edge impound the soil. The size of the dikes, size is 1 m and the freeboard* 0.3 m, the design for dike height. 1 m x 2.2 m) = 3.52 m2, Determine the level using one of the levelling methods Paddy ponds are embankment ponds built over flat ground. 2 = 0.99 m2 and volume for wall 15. out and measuring pond and dike shapes. Check Hand compacting is generally suitable for small dikes, side slopes steeper than the dike itself. for one year. to control depths, heights and slopes with great precision. outlet structure(s), as necessary (see later chapters). m3. the water, as they will have to be regularly cleaned by hand. gravel, sand, sediment, stumps, roots and organic matter. Proceed as follows. Check water table variations on the site (b) Method 2, for horizontal ground, uses average ground as when the pond is set at an angle across the slope, the same method 19. Build the water control with tall stakes and a line. the cultivation of a crop (see also Section 5.6). four dikes of approximately equal height. perimeter dikes EGHF and the perimeter or intermediate dikes AE, 1. then used in the construction volume of the dike. This situation You can calculate the volume of material required (You could use a plough or a hoe.). Use thin layers, wet them if necessary, and compact well. ensure easy and complete drainage of the pond. A 400 m2 (40 x 10 m) area is to be excavated, 1 m deep, Stake out the pond bottom to clearly indicate Divert the stream to a site as close as possible to one (greater than 1.5%). 740 m3. of the cut depth (see Section 6.4). 1 square of 0.5 m x 0.5 m = 0.25 m2 (d) Fill the pond again very slowly and up to a maximum level about measured along the centre line (in m). Usually the bulldozer 9. 2:1, crest width is 1 m. (b) If the side slopes of the dike are not 2:1, multiply the standard Section 3.6, Topography). soil volume or the original soil volume. more or less fixed at a specified level necessary top of the dikes as indicated on the centre line stakes. formula: V = 0.33 x h x S1h x S2h. to anchor the dike to its foundations. = 16 m2; A3 = 18 m2 ; A4 on irregular ground using a scale drawing, Calculating the cross-section of a dike keep any part of it from sliding away, (see outlet trench. On more steeply sloping ground (steeper than 10 percent B Wet zone of dike in sandy soil (a) Draw a horizontal line from D, meeting AE at E'. 7. 3. enough to provide the required water. the cross-section at each end of the excavation. cutting each slope at its planned angle. When disturbed earth is compacted, for example during Crest width = 1 m (b) Calculate the corresponding dike volume using the freeboard being added above the maximum level of the Its main purpose is to reduce water seepage under the dike. because of the need to import the soil material or to find it near the sections, compacting well. (a) Tidy up and shape the course of the old stream bed. 2. Average length = (top length EF + bottom length E'F') 2 = (40 Average area for wall AB = (1.5 m2 + 0.48 m2) along the centre lines of the dikes and by setting out straight When the construction site has been prepared, the fish pond and its You can quite simply 12. can be used. Stake out on the ground points G, H, I, K on the wet side and L, The core is built together with the rest of SH = Settlement height Never plant large trees on or near dikes because their roots would 2 (D and C) respectively. of 1.5 m and a crest width of 1 m. Pond area = 20 x 20 m = 400 m2 If digging depth = 1 m, dike height = 1.5 m - 1 m = 0.5 m. Using In several areas certain groups of ponds may have preset levels In barrage ponds with a spillway, the design (see paragraphs 13 and 14) or mechanically (see paragraphs 19 ponds, the pond bottom may be horizontal. However, as the side slopes of the dikes have to be cut below reach rock. This chapter shows you how to construct and therefore the top of your dike should also be horizontal, (a) On the top of each dike, set out the planned dike crest width, the first table, S = -0.05 m and correct the standard cut depth The bottom of the pond now has to be finished; which is done using volume of corner cut Levels should determine the balancing minimum cut and the corresponding dike volumes. on location, pond type or size, or method of operation. pond to be built, you should select the best method to be used. to build small dams only, their height being limited to 2.50 m. If you 6.1). it repeatedly. You can also use the graphical method explained earlier As shown, a clay core will construction height (CH in m) multiplied by slope ratio of. (a) Prepare good foundations, extending them sideways well Note: usually the pond bottom in drainable ponds is given Trenches for dike material should not be cut with Note: in this manual, for barrage ponds you will learn how + (CH x SW). from ground surface to pond bottom. least 1.5 m wide) along the centre line of the dam (see Section 6.3), In certain barrage ponds where the upper shallow areas are It will (e) Build the water outlet structure (see chapter section). = 1.20 m, wet side slope = 2:1 and dry side slope = 1.5:1, then volume by C (crest factor), obtained from Graph The calculation method depends You can then at each part of the dike base on either side of the centre line, as the soil from within the pond area. Note: you should always ensure that the entrance of the as follows: (a) Deepen and widen the channel as necessary to remove all stones, the entire bottom area (see Section 6.10). Similarly, the dike base width also varies. You can calculate the volume (c) If you have to use various types of soil to build the dam, use 14. (c) Average length can be determined at the midpoint. 1 m) + 2 x (0. During this period, check the dikes carefully. line*, progresses through the dike so as to remain inside. It also shows the effect of various degrees of compaction and 17. pond, although here only one template size is required. hence the balancing depth. When using machinery to build the dikes of a cut-and-fill pond, (0.2 percent) or, preferably, dig a network of shallow drains with a slope of 0.2 percent over (d) Compact the whole area well after wetting, if necessary, and erosion becomes stronger; as the slope ratio increases, the volume of earthwork increases, + An-2)]. Graph 4). To estimate the volume at each corner, use the 6. limit by 0.20 m x 2 = 0.40 m and the outside limit by 0.20 m x 14. For the previous example, Graph 3a shows a standard If the pond was not 20 x 20 m but, for example, (. grading usually flattens off the slope. its potential for compaction by measuring out a known volume of material Note: cut-and-fill ponds are generally of the diversion Method 1 with volumes calculated as described in Section from the pond water depth. the dike, using different types of soil for each 0.20-m layer. the inside limits of the dike's base. one of the following methods. described for paddy ponds (see Section 6.7), checking the pond bottom 15.2 squares x 0.25 m2 = 3.8 m2. with the following characteristics: 9. height) x (wet side slope)], Example of dike base on very irregular = 100 m2. Determine the width of the crest according to It is best to observe the site spreading it on the dam and planting grass (see Section (b) Dig at least 30 cm below the original channel bed or until you You can check these results with a third set of calculations, Do this on Use several sections to calculate volume 4. by adding: For the above 0.04-ha pond to be built in clayey soil, Note: a difference in elevation than you dig out to fill the same hole. 21. (b) Multiply by the average length of the excavation. predation; to make edges shallower for good fry feeding. a certain volume of soil necessary to build the dikes above ground level 6. of the previous two methods. Note: for ground slopes of less than 10 percent, and where required and, if available, some squared or graph paper for sketching 37. balance using Method 1. to be reduced by either compaction plus final/small settlement, Before starting the construction of your pond, you should calculate by penetrating too deeply or disturbing the soil. Seed or plant grass to control erosion (see Section 11. to those in perimeter dikes, and the dike should be stronger. at AB and CD, and average length. Correction factor S for dike slope Dike height = 1.40 m. (b) Calculate for each pond corner the width of the dike base This task will be much easier if you have fast spread into a dense cover, through creeping, rooting stems perimeter dikes EGHF and the perimeter or intermediate dikes AE, Average output per working hour (m2/h variable level, the width of the dikes at the base varies from one pond 34. Extend the trench sideways, well into in the case of a barrage pond, you must prepare the channel of the stream 4. the methods described in Section 6.4 obtain, according also be additional small volumes to allow for in making pond shapes (a) In Graph 5 enter the area of the pond (in m2) on both side and end are S1 = S2 = 2:1, keep any part of it from sliding away. 1.5:1 (outer), this is multiplied by S = 0.9 to give 720 m3 to be built for a barrage pond, 20. ratios, 2. where digging depth = 0.72 m and dike height 1.50 m - 0.72 m = 0.78 cover on pond dikes are listed in Table 30. (c) Calculate V = (10 m 3) [10 m2 Note: these dimensions may be slightly reduced for be found or used in the rest of the project. 15. for them to function properly. two toelines on a series of perpendiculars set out at regular showing how to clean and enlarge the old stream channel. 32. soils concerning: 5. Crest width = 1m 4. above the line are approximately equal to those below the line.

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