Intake structures for capturing groundwater
The groundwater abstraction is a complex of waterworks, comprising a meter device for taking water from an aquifer, a pumping station to lift water, the conduits for collecting and transporting water in the building to improve its quality or to the reservoirs.
The type and layout of water intake facilities selected on the basis of geological and hydrological conditions. The type of construction depends on the depth of the aquifer, its capacity and voodoobilly, the conditions of deposition (the nature of the rocks, the presence of pressure in the reservoir, etc.). Structures used to capture groundwater that can be divided into the following groups: wells (tube wells), dug wells, horizontal water supply wells, intakes, radiation, capture sources.
Water wells – wells for sampling groundwater, equipped, as a rule, standing pipes and water-intake devices, mainly filters. The basis for calculations water supply wells based on hydraulic and hydrodynamic methods to estimate the reduction levels and (or) pressures in the intake device at a given flow rate in different periods. Well yield – the volume of water given by the well per unit time.
Depending on geological, hydrogeological and sanitary sloveniana defined well structure (Fig. 4.11), its depth, the column diameter of pipes, type of water intake part of the intake and tip well (Fig. 4.12).
Fig. 4.11. The scheme of construction of well:
1 – conductor; 2 – technical column 3 – maintenance column 4 – annular cementation; 5 – coupling; 6 – stuffing box; 7 – filter the first column
Fig. 4.12. Design of intake wells:
a – above-ground pavilion; b – underground camera; 1 – water – lifting pipe; 2 – casing; 3 – control Cabinet; 4 – the pump motor; 5 – plunger; 6 – differential pressure gauge flowmeter
When designing water supply wells should consider the conditions of their interaction with existing or planned water intakes, as well as their impact on the environment.
In the well design should provide for the possibility of carrying out measurements of flow, level and water sampling, and production repair work.
The diameter of the production casing tubes in wells should be taken when installing the pumps: borehole with a transmission shaft (engine installation over the wellhead) by 50 mm larger than the nominal diameter of the pump; submersible – equal to the size of the pump.
For fastening of wells using casing steel sleeves and welded tubes. For fixing wells up to 250 m in loose fit casing it is allowed to use non-metallic pipe with a required annular cementation.
When drilling, we should prevent the penetration of surface contaminants and water, unused aquifers in the well.
When the unit wells in loose, unstable rock and half-rock rocks, you must install filters that prevent the borehole from the entry of soil particles from the aquifer. The correctness of the chosen design and installation of the filter to ensure the reliability of the wells.
The type and design of the filter will be based on aquifer rocks. A water intake device – different types of filters should be maintainable, i.e. to ensure the application of the impulse, reagent and combination (pulsed-chemical) ways to restore the capacity of the intakes. After installation in the bore of the filter is carried out by experienced pumping to determine the specific well yield.
Water-lifting devices and equipment management depending on local conditions you can place in the pavilion (see Fig. 4.12, a) or recessed (see Fig. 4.12, b).
Wells recommended for sampling water, usually in the first from the surface unconfined and shallow aquifers, lying at depths up to 30 m.
When aquifer thickness to 3 m suit wells of the perfect type with the opening of the entire formation thickness; if a higher capacity is allowed perfect and imperfect wells with the opening of the stratum.
Wells . usually perform circular shape in plan with a diameter of from 1 to 2.0 m. the sides of the well may be of brick, rubble, concrete, reinforced concrete, wood. In Fig. 4.13 shows a diagram of the device of mine wells of precast concrete rings with a diameter of 2 m and height 1 m.
Horizontal water intake (GW) used for the abstraction of water from shallow aquifers with a small capacity.
They consist of an intake structure, taking water from an aquifer; drainage canals or pipes to drain water collected into the drainage pit, drainage wells and pumping stations.
On the basis of unit inlet horizontal intakes can be divided into open channels, stone-crushed stone drains, pipe drains and galleries.
For temporary water supply used stone gravel horizontal intake. Water from a stone-and-gravel drains water intake is part of stone-crushed stone prism, built of ragged stone or crushed stone of size 30 × 30 or 50 × 50 mm, laid in trenches. Before backfilling, you should have a screen of clay or loam as to prevent the ingress of surface water into the trench.
The most perfect horizontal water – tube drain. The inlet tubular drains are made of perforated concrete or reinforced concrete pipes. Minimum pipe diameter of 150 mm. the lower part of the pipe (not more than 1/3 of the height), through which flows the collected water, has no holes. Pipes are laid with a slope of 0,007. Of 0.001 in the direction of drainage of the well. The rate of flow of water in pipes should be not less than 0.7 m/s.
In particularly important water systems arrange the drainage gallery of precast concrete elements. Gallery width of 0.8 was adopted. 1 m, height 1.2. 2.0 m.
Water-intake device of horizontal water intakes should be placed across the movement of groundwater flow for a more complete capture.
Radial intakes are structures consisting of a shaft well and a system of horizontal wells extending from the lower part of the shaft (Fig. 4.14).
A water intake portion of the intake – horizontal tubular drains (rays) radiating from the mine pit and laid in the aquifer by forcing. The bursting rays is carried out from shallow wells. Radiation filter pipe made of a perforated (slotted) steel pipes. Horizontal radiation from the filters the water enters the mineshaft.
The use of radial intakes for intake of hyporheic water can get clean water from rivers and lakes by filtering it through a bed and banks.
Meter installations water abstraction spring water are a camera type wells arranged in place of water present on the surface. By type of education spring flow springs can be divided into ascending and descending. Updrafts are formed as a result of a violation of the layer overlying confined aquifers. Descending spring waters are formed as a result of seepage to aquifers (for example, on the slopes of the banks of ravines, gullies, hills). The damming is in the opening and the device structure, providing the most complete use of the source and its protection from pollution of surface waters. The design of the meter facility depends on the type of flow.
In Fig. 4.15 shows an example of the capping of thermal spring water that provides the flow of water through the bottom of the well.
1 – supply pipe; 2 – overflow pipe; 3 – well; 4 – vent pipe; 5 – a vegetative layer; 6 – clay-gravel blind area; 7 – hard-Packed clay soil; 8 – rocky ground; 9 – gravel; 10 – the Nagorno the ditch
In the presence of declining use of the spring construction which provides the flow of water through the holes in the wall of the chamber. To best capture downstream capture suit wall. Depending on the power of the spring water they can be used for water supply of small settlements and large cities.