just by using one cross-section. The cross-section of a dike to be built on. volumes can be defined: 4. If the ground slope is very irregular, it is best to proceed slightly that is, whether the compaction potential is related to the expanded Work on the bottom of the pond to make sure the pond 24. earlier removed or is obtained from a nearby source. When the ground slope is steeper than 0.5 percent, you soil in a trench; a hand tamper, a metal or concrete weight (maximum 4 to 6 kg) attached about 0.20 m above the level of the surface of the dike's foundations. 1. using one of the methods described earlier (see Section 6.4, paragraph described for paddy ponds (see Section 6.7), checking the pond bottom the water table elevation with the season. You will normally have to remove the topsoil (d) Stake out the dikes' bases all around the pond, on short perpendiculars variable level, the width of the dikes at the base varies from one pond For reasonably flat, level surfaces, where excavated The dike is 1.40 m high with the following characteristics: Pond area= 25 x 15 m = 375 m2 the pond reaches the designed maximum level. The pond to be built measures 25 x 15 m along centre lines. Use good soil, how much soil you will need to build its dikes. of the pond to form dikes, the trenches created should be linked in (a) At intervals d = 10 m, identify seven cross-sections see Table 30, at relatively short intervals. to the first table given below, using the second table given balancing volume (155 m3). the method described in Section 6.4, paragraph 23, using (d) Transport the soil removed, as necessary. (g) Seed or plant grass to control erosion (see Section + An-2)]. Never plant large trees on or near dikes because their roots would prevents seepage water from washing out the finer dike material. dikes vary in height. the dam, it is useful to place larger grades (such as medium to coarse Building the dikes using soil material METHOD 1 (d) Fill the pond again very slowly and up to a maximum level about If SD = 1.5:1 and SW = 2:1, calculate the base width of the quality of the foundations' soil: 11. elevation for the water outlet pipes. In good soils, this is usually (g) For each dike, move the inside and outside limits toward This expanded volume is (d) Spread this soil material in thin layers and compact it well. for dikes, a method Use several sections to calculate volume Using the figures from the example on paragraph 4, the cross-section (a) Fill the pond with water very slowly and up to a maximum depth areas to obtain A1 = 10 m2 ; A2 either radiating from the outlet if the pond shape is squarish; or in a fish-bone pattern if the pond is more elongated. best results, you therefore should always: Good soil material for compacting will stick together. (You could use a plough or a hoe.). To illustrate method one we will use a 400m2 18). You can calculate the volume of material required pond area to the outside limits of the pond dikes but you would need a sheepsfoot or pneumatic roller (see Section 10.2 It the ground slope is greater than 1.5 percent, the bed of the diversion ditch within the pond area. high ground level and should be lower), or a deficit needs to be made If the site soil was initially loose, you may be able to compact Building a water outlet structure in the Another way to build the dikes of a paddy pond is given here. 69). drainage of the pond along the sloping bottom (see paragraph 14 of this (i) Shape the sides of the pond to the desired slope and finish (h) Dig to the designed depth within the limits of the pond, cutting gravel or small rocks) at the dry toeline. Place the outlet entrance at an elevation low enough to ensure complete along the centre lines of the dikes. compact each layer well (see Section 6.2). the basis of planned dam characteristics (see Section 6.1). of the surplus (the difference between the expanded volume and the original and drainage canals have to be built at the same time, so that the earthwork the change in horizontal distance (z in m) per metre of vertical distance on rough ground, you should apply the following formula, known as Simpson's You are now ready to finish your barrage pond. less than 0.5 percent. (d) Compact the whole area well after wetting, if necessary, There are several ways to build the dikes of a paddy pond. dike height = 1 m. This time, you obtain: In this case, the fill volume exceeds the cut volume. 38. Calculate distances from the centre line to the regular, you can calculate the volume of the dike (in m3) the inside limits of the dike's base. using heavy string or cord. the cultivation of a crop (see also Section 5.6). If in the above example, a side slope ratio of 2:1 is used, and plant or seed grass (see Section 6.9). 1. excavation and dike volumes on sloping ground. 7. For ponds where internal trenches have been dug to provide material can be estimated as: 22. further as 0.728 m x 1.5 = 1.092 m. 1. (d) If you do have relatively permeable materials on the dry side of 2. water behind it (see Sections 1.3 and 1.4). The volumes of earth involved, either the dike's construction height. (see paragraphs 13 and 14) or mechanically (see paragraphs 19 m + 35 m) 2 = 37.5 m. (d) Thus volume = average area x average length = should be established outside the operation radius of the machinery. a more rapid but less precise estimate, see Section 11.3. intervals. on The distance between drains should vary from 4 to 8 m LMNO as follows: 8. You will find it useful to have a notebook in which to make any calculations Notice that the limits of the side walls are according to the size of the canals. As the dike slope ratios differ from those of the standard pond Check carefully the quality of compaction 1. for plates and percussion tampers called frogs. also be additional small volumes to allow for in making pond shapes 80 percent of the previous figure (see paragraph 14). According to the extent have enough impervious soil at the site to avoid excess seepage losses. the shape of the pond is usually either square (minimum earthwork) or (b) Clear all vegetation on irregular ground using squared paper Water supply and drainage canals are usually 11. . the basis of planned dam characteristics (see Section 6.1). Remove any excess soil. This task will be much easier if you have Impermeability of the dike can be ensured by: Diagram of a pond dike built using sandy lines between these new points. cut-and-fill calculations will define the surplus soil produced or the In the previous case, at corner A for example, if side slopes On more steeply sloping ground (steeper than 10 percent Begin building the dug-out pond by preparing the site 9. Alternatively you can arrange for ponds to be at different would be 400 m2 x 1 m = 400 m3). Do this on adjust levels graphically to obtain an approximate balance of the wet side inside the pond and the dry dike, although this method is less accurate. = [(0.36 m3 - 0.30 m3) 0.30 m3] 19. Note: for clays and similar soils, it may be better volume by C (crest factor), obtained from Graph GRAPH 5 According to the average construction you should use Method 1 together with the methods for calculating ponds to be at the same level. (c) Mark a parallel line on each side of this outlet calculated most easily using a scale drawing. 3. during a complete annual cycle to check on the possible variations of 6. m x 1.5) = 0.5 m + 1.80 m = 2.30 m; and similarly all around 60 cm vertical by 180 cm horizontal gives + 4(3.1 m + 2.1 + 2.5)] = (100 m2 4) x [(12.8 m) + 2(20.9 of the area toward the dry side of the dike. Use average ground and dike levels for the group dikes. [(6.375 m2 + 11.375 m2) 2] x 37.5 m = of the dikes needs to be level, but as the base of the dikes is on a (e) Again, plot these values on the two-way graph (see You can estimate the bulking of any earth material and determine As shown, a clay core will Crest width = 1 m 8. Trenches for dike material should not be cut with The downslope dike will be the highest above This, together with the height of the dike, will determine be that the last soil layer is less than 0.20 m thick, in which TABLE 29 (c) Build up the second part of the dam, being particularly Build the dikes as explained earlier in this section, either manually the example. (d) If the height of the dikes is not 1.5 m, multiply the through the site or through groups of ponds. lengths of the base and the corresponding cross-sections, as calculated so that the surface materials of the foundations are as well compacted (a) Stake out the centre lines with a series of pegs. (b) Dig at least 30 cm below the original channel bed or until you B Wet zone of dike in sandy soil the steeper the slope, the more easily it can be damaged; as the soil becomes more sandy, its strength decreases, and slopes 3c. 23. required, adapt the size(s) to the size of the dike. You can determine the construction height (CH in m) simply on the ground before starting the construction. is to calculate one pond at the top end of the site and another at the it over the entire area into a layer about 0.20 m thick, wet it if necessary, for its construction; excavated ponds, to provide the pond volume required; other structures such as harvest pits, supply channels, etc. is determined for each pond corner, and therefore their corresponding Determine the level using one of the levelling methods Here each pond is calculated individually. Levels should If you do not have enough good soil to of the earthwork involved, rough estimates may be obtained by using Then, proceed how deep to dig at a series of points (see Section 11.4, as volume by P (pond shape factor), obtained from Graph
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