Effective dewatering: wellpoints, the principle of their operation and the advantages of using

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High ground water contentcomplicate economic activities, fill pits for future facilities, complicate the construction process, reduce their reliability and durability, undermining the foundation. To make this or that site suitable for construction, preliminary water-downing is carried out. The needle filters used to reduce the water level allow you to accomplish the tasks even in the most difficult hydrogeological conditions.

The basic principle of dewatering

The choice of a specific method of dealing with highgroundwater depends on such parameters as the size and depth of the pit, the design of the future building, the current geological and hydrological conditions, etc. However, any water reduction technology is used with one goal: lowering the level of groundwater to a depth at which they cannot obstruct the construction work.

The general principle of all water-reducing methodsis to create a depression funnel. With constant pumping, the water in the soil layer forms a kind of funnel. In the place where the water fall is performed, the acupuncture filters form the center of the depression. The difference between the required water level and the lower point of the funnel-shaped depression is called the depression funnel.

The depth and radius of the depression funnel is given independing on specific requirements and conditions. These parameters are maintained for the entire period required for construction operations. It is important that the dewatering of the needles should be permanent, since if the pumping is stopped, the groundwater will rise to the original level.

Needlepoint design

These devices consist of a pipe, onthe suction end of which is installed filter. Due to the presence of the filter, solid particles (soil, sand, fragments of various rocks, etc.) do not fall into the needle filter installations.

The diameter and length of the pipes are determined depending on the depth of the future pit, the properties of the soil and the required throughput.

water reduction with needlepoint filters

Algorithm of work of points

The calculation of the number of needle filters is carriedtaking into account the required diameter of the funnel. In the vertical position, the equipment is installed in the ground at the place where the dewatering will be carried out. The needle filters through the pipeline is connected to a pump for pumping water. The pipeline can be made of rubber, metal or other types of pipes. The main thing is that they are reliable.

The extent to which water drop will beeffective, depends on the proper selection of pump power and proper calculation of the number and diameter of suction pipes. However, sometimes it is not possible to produce a complete drainage of aquifer soils, as a result of which a certain layer of water (0.5-1 m) remains above the aquitour. Its removal is usually carried out by arranging temporary open drainage systems and using mobile pumping units for pumping water from them.

Methods of dewatering with needlepoint filters

There are various methods for reducing the level of groundwater with the help of needle filters.

If construction is requiredslight water drop, needle filters and self-priming pumps are lightweight. Such equipment will be able to reduce the level of groundwater to a depth of 4.5-8.5 m. If it is necessary to carry out a dewatering operation, special needlepoint filters with a multi-tiered structure are used up to the maximum depth.
If the groundwater level needs to be reduced to a depth of 18-20 meters, ejector syringe filters are used with a special water-jet pump — an ejector.
Deep-well centrifugal pumps are used for dewatering to a depth of over 20 meters.
Vacuum method based on usespecial ejectors that create a vacuum in the locations of the filters. Such systems can effectively reduce the level of groundwater in hydrogeological conditions of increased complexity.

The choice of a specific method of water decreasebased on the characteristics of soils, their occurrence conditions and the thickness of the aquifer. In addition, the required filtration coefficient, the area of the drained zone, the production technology of construction or mining works, the duration of the water fall and the characteristics of the water lowering equipment are taken into account.

Installing the needle filters

The choice of installation method for water-reducing equipment depends on the soil characteristics at the site of future construction work.

Hydraulic installation method is used whenthe need to reduce the occurrence of water in sandy and fine-grained soils. This technology involves the injection of water into the filtering device, which then falls into the ground.
The mechanical method of installing acupuncture filters is recommended for dewatering in gravel and clay soils. For drainage pre-drilled wells with the help of special equipment.

The best way to install the needle filters and their number is determined by the size of the drainage area and the characteristics of the soil.