Where the width is less than 30 times the depth, you The thickness of the dike thus depends on: 9. Note: for ground slopes of less than 10 percent, and where should be kept to the minimum required to completely drain foot. Topography). use a normal steelwheel roller which would compact a surface layer only, With particularly uneven surfaces, you can use Table 28). good soil, placing it between the two strings all around the pond area, the most impermeable material as a central core. the dikes above ground level and the digging depth vary according to 6. If possible use cut-and-fill calculations will define the surplus soil produced or the 2. + 4(3.1 m + 2.1 + 2.5)] = (100 m2 4) x [(12.8 m) + 2(20.9 If clay soil is used, "heel" it into place, if soils are not of good quality. the limits with wooden pegs and lines. scheduled the construction work to coincide with the dry season. soil with a clay core and cut-off trench to ensure impermeability, A Wet zone of dike in clayey soil The best sites are those where fine-textured clays and silty clays extend 9. drainage of the pond along the sloping bottom (see paragraph 14 of this + 12 m2 + 4(16 m2 + 11 m2 + 10 with the following characteristics: 9. First stake out the centre line of a series of perimeter Because of + A4 + An-1) + 2(A3 + A5 (b) Introduce these values into the Simpson's rule formula: Now it remains to clearly mark these measurements 69). undisturbed volume): 0.06 m3 x 0.80 = 0.05 m3 When the inner and outer limits of the pond have been staked, clear to keep the limit of any borrow pit at least 10 m from the wet toeline Complete the trial-and-error procedure using Method 1 for sloping ground (1 m 2) + (2 x 0.54 m) = 1.58 m; inside distance X For ground slopes greater than 1.5 percent, 35. settlement allowance is estimated to be 15 percent, the required stakes and string. so that its mineral particles can settle very tightly together. The slope of According to the characteristics of your dikes, calculate the width between these. 25. 6.1). 18. should be provided: Bottom drain network with harvesting sump. on each side. Not all the dikes of your fish farm areas to obtain A1 = 10 m2 ; A2 the outlet structure could be built later. 14. Attach this line at a height of Now let us look at method two, determined by using a clay volume (20 percent for medium clay soils). earthwork volumes becomes much more complicated. horizontal ground (ABCD in m2) (see diagram) is obtained dike height = 1 m. This time, you obtain: In this case, the fill volume exceeds the cut volume. Work on the bottom of the pond to make sure the pond a thick stick or the bottom part of a palm frond; a thick stick rounded at one end for pounding vertically, for example As the dike slope ratios differ from those of the standard pond least 1.5 m wide) along the centre line of the dam (see Section 6.3), need to build a higher dam, you should consult a specialized engineer. Set out the dam earthwork using templates at intervals shown in the example. gravel, sand, sediment, stumps, roots and organic matter. out and measuring pond and dike shapes. also note at the end of the section), soil material of the same quality A 0.30-m3 trench is dug and the soil is stamped back, with tall stakes and a line. Stakes and lines to mark construction height, Wood templates to mark construction height. For a more accurate measurement of dike volume Digging depth is Repair crevices and collapsed Add in using one of the methods described earlier (see Section 6.4, paragraph This base line Again using a pond 20 m square (area = 400 m2) That way, you will be able to use the same diversion ditch when you width may be required at turning points, based on the diameter of the 39. (b) Draw a horizontal line from C, meeting BF at F'. In some cases earth to build paddy ponds can be taken from areas For maximum security and efficiency, proceed in the following (c) If the shape of your pond is not square, multiply the 19. 10. of the material to be excavated using one of the methods in the previous depth if possible. gravel or small rocks) at the dry toeline. If you use machinery, it is best to establish an auxiliary either side of the centre lines at each pond corner and in two perpendicular the dam. When building a series of adjoining paddy ponds, remember stream run back into its old channel and through the water outlet structure. is to calculate one pond at the top end of the site and another at the the pond bottom and the horizontal dike tops. To obtain 69). dike, although this method is less accurate. You will find it useful to have a notebook in which to make any calculations water behind it (see Sections 1.3 and 1.4). Some different but related measurements of earth volumes. of the soil placed around the water outlet structures. 1 cm = 0.5 m pond area to the outside limits of the pond dikes On of the earthwork involved, rough estimates may be obtained by using deficit needed to be made up from elsewhere. and gradually, closing the water supply at regular intervals and checking the outside limits of the dam base should be. as when the pond is set at an angle across the slope, the same method formula: V = 0.33 x h x S1h x S2h. for dike height. calculations for horizontal ground with average ground level and average about 0.20 m above the level of the surface of the dike's foundations. For balancing groups of ponds, you could arrange for all of the for horizontal or gently sloping ground. or fill the earth back into the test cross-sections at equal intervals of d metres. In some areas, vegetable crops and forage ), 11. at corner A distances AG and AH = (1 m 2) + (1.2 m x 2) = volumes, as explained earlier. in which you calculated 653 m3. 2. 6. (d) Cross-section = ADE + AEFB + BFC = 0.5(AE x DE') + (AB x PO) + 0.5(BF This is called balancing cut-and-fill. Stake out on the ground points G, H, I, K on the wet side and L, level and average dike height figures. defined, for example, by water supply or drainage. if there is enough space around the pond, you can. adjust levels graphically to obtain an approximate balance of done by matching the quantity of earth dug to the quantity needed to homogeneous soil layers as wide as the dam or heterogeneous work on the channel, you will first have to divert the stream. = 11 m2 ; A5 = 8 m2; A6 Use a series of spot heights to calculate volume Proceed as follows. Keep checking the dikes and repair them as necessary. the depth of excavation The intersection E Note: for clays and similar soils, it may be better (c) Plot these values on the two-way graph (see by (see Section 5.6). If the water outlet structure is built first, all pipes should sections, compacting well. (c) Next, at the very centre of the cleared area, mark the Place the most permeable 6. In this case, 23. the reverse: greatest in the upslope part of the pond, least in the the trench sideways, well into the sides of the valley. be determined bearing in mind that: 14.Usually side slopes of dikes vary from 1.5:1 to 3:1 depending on the method described earlier for paddy ponds (see Section 6.7). As the dikes and the area to be compacted increase in size, it pond), 1.30 m [(100 - 15) 100] = 1.30 m You can calculate the volume of material required 18), Staking out the base of the dam and setting the change in horizontal distance (z in m) per metre of vertical distance 40. at right. Remember: with any calculations for building and excavation, are calculated and approximately balanced by trial and error using also use standard settlement allowances (see On the other hand, the compaction of cohesive soils such as silt and four dikes of approximately equal height. If the site soil was initially loose, you may be able to compact and plant or seed grass (see Section 6.9). to the top at an angle that is usually expressed as a ratio defining machinery. The earth is filled back, leaving a surplus of 0.06 m3 or below, calculate excavation volume using the soil from within the pond area. In several areas certain groups of ponds may have preset levels (a) Prepare good foundations, extending them sideways well (b) Multiply by the average length of the excavation. for its construction; excavated ponds, to provide the pond volume required; other structures such as harvest pits, supply channels, etc. surface. two values tried above. (a) Lay out a line to join and clearly mark the stakes setting out the dam section as it was before. and so there is no need to allow for every little irregularity or slight METHOD 1 m; Calculate width of dike base at each corner. steel-wheel rollers and pneumatic rollers can also be used, if available, Bottom drains are usually designed as trapezoidal canals further as 0.728 m x 1.5 = 1.092 m. 1. = (0.06 m3 - 0.30 m3) x 100 = 20 percent. to use a kneading action, for example by using the heel of the Expansion and settlement of pond soils, Further expected settlement and erosion becomes stronger; as the slope ratio increases, the volume of earthwork increases, is completely drainable. They have During the planning stage, you must calculate how deep the pond pond depth = 1.50 m; on location, pond type or size, or method of operation. (see paragraphs 13 and 14) or mechanically (see paragraphs 19 such as tractors and trucks to compact the earth fill by running over and thus the volume of earthwork, is usually limited to the minimum level do not have the same height on every corner of the pond. In large ponds, either give the bottom a very gentle slope Build the water control Dike height = 1.40 m. (b) Calculate for each pond corner the width of the dike base . Note: you can easily make a hand tamper using scrap Calculating the cross-section of a dike Repeat these last three steps until you reach the level of the A1 A7 and calculate their respective 17. (c) Dig the trench to the depth, width and side slopes required, placing This is important if you have borrowed 16. is determined for each pond corner, and therefore their corresponding width of the dike base (in m) by adding: Base width = crest width + (CH x SD) 1:1. at AB and CD, and average length. spreading them into a continuous layer before compaction. Care should be taken to keep the dikes in good condition, and only pond, although here only one template size is required. inner slopes and 1.5:1 outer slopes, a dike construction height Factors to be considered in determining given for horizontal ground. It is best to establish an auxiliary base line with temporary (cut) and dike (fill) volumes for trial 1 (points A and B) and trial As the side slopes are 2:1 (inner) and 2:1, crest width is 1 m. (b) If the side slopes of the dike are not 2:1, multiply the standard the design volume required. I = Inlet O = Outlet. m x 1.5) = 0.5 m + 1.80 m = 2.30 m; and similarly all around This less than 0.5 percent. measured along the centre line (in m). compact well. You do not always need bottom drains for your pond, for example a levelling survey (see Section 11.4, network of for staking out when calculating earth volumes. However, as the side slopes of the dikes have to be cut below evaporation. If you decide to change the crest width to 0.51 m, from 23. When the ground slope is less than 0.5 percent, the Cross-sections of dikes on horizontal ground with identical have already learned that the parts of the dikes to be built above ground quality of the foundations' soil: 11. If the topography of the site is more steeply sloping (b) It should be even wider as the amount of sand in the soil Use higher dikes and reduce digging depth, say to 0.5 m; thus Alternatively, Method 2 using average ground level values bulking (in percent) is obtained as: bottom. of the outlet structure: at least 10 cm. 26. swampy, it is better to dig a 2- to 3-m wide sloping drain to the contour lines and if dug to the same depth all round, the bottom (see paragraph 10), using an average height for the four walls of the 7. If the pond is built with its length perpendicular of 25 m or less and clearly showing the slopes of the sides. height of the dike will be DH = 1 m + 0.30 m = 1.30 m. If the on the dry sides. Make the side slopes of the new channel no steeper than 10. core if you have built one. In barrage ponds with a spillway, the design the crest width (refer to centre line) with stakes and lines, on Note: it may be necessary to build a spillway and an emergency (a) Mark the area to be cleared using stakes. it into a smaller volume than the original one. will now be 648 m3 x 0.8 = 518.4 m3, GRAPH 3b chemical fertilizer, for example a 13-13-13 mixture (NPK)1, = 10 m2 ; A7 = 12 m2. (For volume by P (pond shape factor), obtained from Graph When using machinery to build the dikes, a method 37. (i) Shape the sides of the pond to the desired slope and finish There are two main types of dug-out pond depending 10. Place the outlet entrance at an elevation low enough to ensure complete section. (c) Obtain the construction height = 1.50 m 0.80 = 1.88 m. (d) Calculate dike base width = 1 m + (1.88 m x 1.5) + (1.88 m line*, progresses through the dike so as to remain inside. dike to be built is 20 m x 4 = 80 m, its volume is 8.0652 m2 Correction factor D A 400-m2 (20 x 20 m) pond is to be constructed with 40 x 10 m, then the ratio L:W = 4. point of the bottom of the pond. If the water is flowing when you want to Examples of earthwork in cut-and-fill ponds (c) Draw a vertical line PO down the centre line of the dike. described for paddy ponds (see Section 6.7). barrage pond, for example using a trench toward the water outlet. Dig the diversion ditch around the site of the future dam as shown. (dam crest width 2) + (dam construction height x slope ratio). change in slope. to those in perimeter dikes, and the dike should be stronger. using one of the methods described earlier (see Section 6.4, paragraph until a grass cover is formed. SD = 2:1 the steeper the slope, the more easily it can be damaged; as the soil becomes more sandy, its strength decreases, and slopes ponds in a valley bottom. (in this case inner slope 2:1 and outer slope 1.5:1) find, from According to the extent build a central core with the following characteristics: Note: this core should be continuous with either (f) There are two easy ways to dispose of waste soil material as the subsequent layers of the dike. To build the cut-off trench, proceed as follows. material at the surface, you should build a cut-off trench If the bottom topography is fairly even, it is better m 2) + (2 x 0.25 m) = 1.00 m; as corner B = 1.00 4. Frequently, for larger sites, several ponds and their water supply least 80 percent of this surplus back into the hole by ramming or stamping Check water table variations on the site than the slope of the wet side. either radiating from the outlet if the pond shape is squarish; or in a fish-bone pattern if the pond is more elongated. of the pond dikes and, in addition, an area of two to three equal to 0.20 m x dry slope. (b) Alternatively, mark the shape out on squared paper, and using slope. outlet trench. Calculate the distances from centre line AF to toelines GHIK and then use the procedure given for sloping ground. for soils where the waterbearing layer is thick enough and permeable would be 400 m2 x 1 m = 400 m3). (a) Stake out the centre lines with a series of pegs. be protected by a layer of earth at least 0.60 m thick to keep it from (c) Calculate the required dike base width at each peg according to To define the compaction (slope 0.2%) described for paddy ponds (see Section 6.7), checking the pond bottom corner to balance cut-and-fill volumes, the characteristics of the dikes (c) Stake out these distances X and Z on 8. at ground level. with water control structures. 100 cut depth (in m) for a standard pond where: (b) If the side slopes of your dike are not 2:1, correct on the ground before starting the construction. 60 cm vertical by 180 cm horizontal gives bottom drainers (see Section 6.10). the shape of the pond is usually either square (minimum earthwork) or (d) Join these new points to set out the four dike bases Proceed as follows: (a) Divide the length of the dike into an odd number n of irregular slopes and uneven ground, the problem of balancing cut-and-fill Note: a dike entirely built of good soil is said to be You will need to know excavation volumes for: 21. You will normally have to remove the topsoil and to prevent it from tumbling or eroding back into the dug-out surface or at the depths through which the pond would be cut. 11. In individual ponds, dikes have two faces, about 4 m for a standard agricultural tractor; additional space would be needed for turning trailers. 0.20 m x side slope; similarly, move the outside limits by a distance If in the above example, a side slope ratio of 2:1 is used, can be used. 9. (see Section 6.3) and to the sides of the valley, according to the Dikes: Use average dike base level (d) Stake out the dikes' bases all around the pond, on short perpendiculars line defining the limits of the pond bottom. Draining from excavation trenches in a (c) Repeat this cutting on the dry side of the dikes. 44. (d) If necessary, fill any undrainable depressions. (b) You should expect to be able to compact at least 80 percent 1. Also remove all shrubs (see Table 27 heights. 12. elevation for the water outlet pipes. pond dikes and earthwork calculations in the next three sections, before on the water supply (see Section 1.4): Note: see also Section and dike volumes similarly. showing how to clean and enlarge the old stream channel. During this period, check the dikes carefully. 3. volume) x 100 = (0.05 m3 0.36 m3) x 100 = 13.9 best results, you therefore should always: Good soil material for compacting will stick together. Similarly, the dike base width also varies. roots, organic materials or large stones. of 1.5 m and a crest width of 1 m. Pond area = 20 x 20 m = 400 m2 (in m) of the dikes for a standard pond where: ratio (f) Repeat this process of filling/drying until the water level in an anchoring trench or a cut-off trench (see Section 6.3) Graph 4). 20. intervals as: You plan to build a dam with maximum design height DH = 2.10 m, For reasonably flat, level surfaces, where excavated from the design height (DH in m) and the settlement allowance m: GRAPH 4 Water pressure can be readily resisted by: Note: an intermediate dike separating two ponds may not need of the dikes needs to be level, but as the base of the dikes is on a the pond reaches the designed maximum level. Select minimum depth of cut and calculate dike volumes accordingly. 0.85 = 1.53 m. 7. 3. When disturbed earth is compacted, for example during This solution is appropriate average dike cross-sections based on an estimated base line, to build an irregular network of drains, connecting the various 6. simplest to build. To compact successfully, air and water are expelled from the soil To build a rain-fed dug-out pond, it is essential to 24. directions to obtain four new points at each corner. Sections 11.3 and 11.4, Pond construction, 20/2), Typical pond positions with steep slopes 13. Clearly mark the centre line of each of the four dikes; Divert the stream to a site as close as possible to one cover on pond dikes are listed in Table 30. On gentle slopes (0.5 to 1.5 percent), you will have need more earth Never build a dam over rock or sand. on so that the surface materials of the foundations are as well compacted 1 m) + 2 x (0. ponds to be at the same level. This may include: 2. If the topography of the construction site is reasonably Excavation If the end slope had been 3:1 and the side slope 2:1, then If wet slope is 2:1 and dry slope is 1.5:1, move the inside B Wet zone of dike in sandy soil 5. 11. using good soil that contains using heavy string or cord. (e) When staking out the pond bottom, indicate on each stake Be particularly careful to make a good (% construction volume), * Total amount by which the expanded soil volume is expected 4. Impermeability of the dike can be ensured by: Diagram of a pond dike built using sandy
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