Highly buried groundwater significantly impedes economic activity, pits 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 reduction is carried out. Acupuncture filters used to reduce the water level, can realize the tasks even in the most difficult hydrogeological conditions.
The basic principle of water reduction
The choice of a specific method of dealing with high groundwater depends on such parameters as the size and depth of the pit, the design of the future building, current geological and hydrological conditions, etc. However, any technology for lowering the water is used for one purpose: lowering the level of groundwater to such a depth on which they will not be able to obstruct the construction work.
The general principle of all water-lowering methods is the creation of a depression funnel. With constant pumping, water in the soil layer forms a kind of funnel. In the place where the water reduction is performed, the needle filters form the center of the cavity. The difference between the required water level and the bottom of the funnel-shaped cavity is called a depression funnel.
Depth funnel depth and radius are set depending on specific requirements and conditions. These parameters are maintained during the entire period required for construction operations. It is important that the decrease in pressure with a needle filter be permanent, because if pumping is stopped, groundwater will rise to its original level.
Needle Filter Design
These devices consist of a pipe, on the suction end of which a filter is installed. Due to the presence of a filter, solid particles (soil, sand, fragments of various rocks, etc.) do not get 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.
Acupuncture algorithm
The calculation of the number of needle filters is carried out taking into account the required diameter of the funnel. In an upright position, the equipment is installed in the ground at the place where the water will be reduced. Acupuncture filters are connected via a pipeline 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.
How efficient the reduction of pressure with needle filters will depend on the proper selection of the pump power and the competent calculation of the number and diameter of the suction pipes. However, sometimes it is not possible to completely drain the aquifers, as a result of which a certain layer of water (0.5-1 m) remains above the water stop. Its removal is usually carried out by arranging temporary open drainage and the use of mobile pumping units for pumping water from them.
Needle filter dewatering techniques
There are various methods for reducing the level of groundwater occurrence using needle filters.
- If minor dewatering is required for construction work, light filters and self-priming pumps are lightweight. Such equipment will be able to reduce the level of groundwater occurrence to a depth of 4.5-8.5 m. If necessary, carry out a water reduction operation to a maximum depth using special needle filters with a multi-tiered design.
- If the groundwater level needs to be reduced to a depth of 18-20 meters, ejector needle filters with a special water-jet pump, an ejector, are used.
- Large-capacity deep-well centrifugal pumps are used to lower water to a depth of over 20 meters.
- The vacuum method is based on the use of special ejectors that create a vacuum at the locations of the filters. Such systems are able to effectively reduce the level of groundwater in hydrogeological conditions of increased complexity.
The choice of a specific method of water reduction is based on the characteristics of soils, the conditions of their occurrence and the thickness of the aquifer. In addition, the required filtration coefficient, the area of the drained zone, the technology of construction or mining operations, the duration of the water reduction and the characteristics of the water-reducing equipment are taken into account.
Installation of needle filters
The choice of installation method of water-reducing equipment depends on the characteristics of the soil at the site of future construction work.
- The hydraulic installation method is used when it is necessary to reduce the level of water occurrence in sandy and fine-grained soils. This technology involves pumping water into a filter device, which is then lowered into the ground.
- The mechanical installation method of needle filters is recommended for water reduction in gravel and clay soils. For drainage, wells are pre-drilled using special equipment.
The optimal installation method of the needle filters and their number are determined by the size of the drainage area and soil features.
Benefits of Using Acupuncture Filters
- Availability of water-reducing equipment.
- Mobility and ease of installation.
- No need to use electricity (needle filters run on diesel).
- Efficiency of work.
- Low cost of water reduction in comparison with other methods.
- High efficiency.