The reservoir is a water storage facility built with artificial materials and has the function of seepage prevention. It is an important engineering facility for rainwater storage.The lack of fresh water resources, water pollution and ecological deterioration have restricted social and economic development to a certain extent. As a low-cost water-saving system, the reservoir has effectively alleviatedWater shortage, solved the problem of citycontrol floodanddrainageQuestion.[1]
According to its terrain and soil conditions, it can be built on the ground or underground, that is, it can be divided into open type and closed type. According to its shape characteristics, it can also be divided into circular and rectangular types. Due to different building materials, it can be divided into brick pool, masonry pool, concrete pool, etc.The layout principle of reservoir is basically the same as that of water cellar.[2]
Open circular reservoir: the tank body consists of the tank bottom and the tank wall. After the tank bottom is compacted with undisturbed soil, it is paved with cement mortar masonry, and then concrete is poured on it.The pool wall has three forms of masonry, brick masonry and concrete, which can be selected according to the local building materials.Structural characteristics: the unit investment of the closed reservoir is relatively small due to the good mechanical conditions;Because there is no top cover, it is easy to build a large capacity pool.
Open rectangular reservoir: this type of reservoir can be divided into brick type, masonry type and concrete type according to different materials.The pool body composition, auxiliary facilities configuration and wall structure are the same as those of the round pool.Its structural feature is that its stress condition is not as good as that of a circle, especially the weak parts at the corners, which need to be reinforced and impervious, especially attention should be paid to prevent uneven settlement between the heavy side wall and the relatively thin pool bottom, resulting in fracture.
Closed graphical reservoir: This form is equivalent to adding a top cover on the open circular reservoir to keep warm and prevent evaporation.In order to reduce the load and save investment, thin shell concrete arch plate or rib arch plate should be used for the top cover, and the pool body should be laid below the ground as far as possible to reduce the thickness and work amount of the pool wall.
Closed rectangular reservoir: This form is equivalent to adding a top cover on the open rectangular reservoir.The top cover is usually a concrete hollow slab or a ribbed arch slab hollow slab with a certain thickness of insulation layer and covering layer set according to the local climate conditions and use requirements.The biggest advantage of this rectangular pool compared with the closed round pool is its strong adaptability. Generally, different specifications and sizes can be selected according to the requirements of terrain and storage capacity, so that the storage capacity can vary greatly.
Pool design
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Site selection principle
The reservoir shall be built at an elevation of 350~700m;Natural villages with relatively concentrated residence and difficult water use;There is natural water (natural rainfall) area and diversion ditches can be built;High ridge with flat terrain or no slip in front and back;Mountain depressions can be irrigated by gravity;It is required that the formation is compact and solid without water leakage;Avoid pollution sources;It is forbidden to build ponds on granular bodies, slope deposits, landslide bodies, and riprap cellars with developed fissures.
Volume determination
(1) Determination of drinking water tank volume
According to the runoff condition, the daily regulation method is adopted to meet the following requirements:
Where, V is the volume of drinking water tank;N is the number of confirmed water demand;T is the water quota.
(2) Determination of irrigation pool capacity
If possible, it shall be determined according to the drought resistance days method, and in general areas, it shall be determined according to the irrigation quota to meet the following requirements:
Where, V is the pool capacity;Q is the daily water demand;N is the irrigation period (5-7d);M is irrigation area;K is the water utilization coefficient, taken as 0.85.
Tank body design
The pool body is composed of four parts: ① the pool body.Generally, bricks, strip stones and concrete precast blocks are used for mortar masonry,cement mortarIt is made by plastering.The wall thickness is 0.25m, the lining material is M7.5 cement mortar, the surface layer is plastered with M10 cement mortar, and finally covered, and a sand basin and diversion ditch are required. ②Outlet.It is set at the normal pool level of the pool wall. ③Pool edge.The pool edge of the fully buried pool shall be 0.25m higher than the ground to prevent the soil and sewage around the pool from flowing into the pool. Generally, it is made of bricks, stones and concrete precast blocks. ④Pool bottom.The bottom of the pool is generally in the shape of a pot bottom, and C15 concrete is embedded at the bottom. It is required to mix evenly. The pouring is mechanically vibrated to achieve a dense and flat thickness of 0.1~0.2m. The surface is plastered with M10 cement mortar.The side wall foundation bricks shall be laid at the same time as the pool bottom pouring, so that the side wall foundation and the pool bottom concrete can be connected as a whole.To facilitate the cleaning and maintenance of the pool, a vent pipe with a diameter of 0.1m is set at the bottom.
supporting facilities
(1) Diversion ditch (canal).It is an important part of the reservoir.According to the terrain conditions, lined ditches can be used to connect the water source with the water storage facilities.The diversion ditch should preferably be connected with the natural rainwater gully on the slope, and the length should ensure sufficient water diversion.
(2) Sand basin.In order to precipitate harmful sediment larger than the specified particle size in the water, make the sediment content of the water meet the water quality requirements and adapt to the sediment carrying capacity of the downstream channel, avoid massive siltation of the reservoir, reduce water storage and increase the dredging workload, so that the flood cement sand on the slope of the sedimentation tank will be deposited in the sedimentation tank, and at the same time, it is also easy to clear.
(3) Trash rack.Trash racks shall be set at the water inlets of sand basins and filters to intercept the dead branches, leaves, weeds and other pollutants carried in the confluence.
(4) Inlet pipe (channel).The following principles should be followed: ① The inlet layout should be adapted to local conditions, the water flow should flow smoothly into the canal, and the shape should be simple; ②When selecting the axis direction, the water inlet shall be smooth; ③When the inlet channel is long, a transition section should be set in front of the control section. The length should be determined according to the flow rate and other conditions, and should be greater than or equal to twice the water depth in front of the weir; ④When the channel needs to turn, the turning radius of the axis is more than 4 times the width of the channel bottom, and a straight section with a length of more than or equal to 2 times the weir head should be located between the curve and the control weir (gate).
(5) Fence.Mainly to prevent people and animals from entering, protect people and animals and project safety, the overall height is ≥ 0.7m, and the solid wall height at the bottom is 0.2m.[3]
