The necessity of conducting quality and effective drilling of water wells on sites with different types of underground soils is due to the development of technologies in this field and the emergence of various methods for carrying out the work itself. One of them is screw drilling of water wells (the other two are column and impact-rope drilling).
Among the main advantages of this drilling method, one should highlight the greater speed of the rig's passage through underground soils, the ability to work in water-saturated layers, as well as the ease of determining the profile for drilling through sand, clay, or other types of cohesive rocks. However, the quality and reliability of the result depend not only on the application of a certain technology but also on the professional training of the craftsmen themselves. This is due to the fact that proper calculations must be made, and during drilling, obstacles and problems often arise that require quick and skillful solutions.
Technological features of screw drilling of wells
Screw drilling is considered one of the most accessible methods, but it can only be applied to rocks with low hardness, such as black soil, clay, peat, sand, etc. At the same time, the depth of installation can reach 50-80 m.
An important nuance concerns the need to eliminate the risk of large boulders and stones appearing in the path of the drilling equipment. As for the diameter, for example, an artesian well can be from 70 to 400 cm, while craftsmen can use additional expansion devices. The immersion of the screw device is ensured by its rotational movements, during which the soil is lifted from the bottom to the surface. This process is important when it is necessary to fix the depth at which the soil layers change. Thus, craftsmen determine the depth of the upper and lower edges of each of the underground layers.
Advantages and disadvantages of screw drilling of wells
Among the advantages of using screw devices, it is important to note:
- high speed of advancing the equipment into the ground (to the source);
- extended service life of the equipment itself, provided that it is used specifically on rocks with low resistance and hardness;
- no need to use additional cooling equipment;
- the assembly and disassembly process of the drilling rig requires minimal time and effort from the craftsmen.
Moreover, the use of screw-type installations allows obtaining a well with a larger (wider) diameter, and the cost of the turn-key well remains maximally accessible.
Among the disadvantages, it is worth noting the possibility of conducting quality work only on soft soils, the need for significant power expenditures, as well as a relatively shallow depth of work. The listed disadvantages significantly limit the scope of application of the screw drilling method, but do not affect the level of its productivity and effectiveness, which is why it remains one of the most popular.
Application areas of the screw drilling method
This drilling option is most often used when conducting various engineering-geological investigations, constructing wells for exploratory purposes, especially in plastic clay soils. Such installations are characterized by ease of control and assembly, and are maximally mobile.
Properties of clay and gravel passage
If the screw drilling system is used on clay rocks, the device quickly jams in the viscous mixture that easily adheres to its walls. To prevent this, craftsmen recommend additionally using crowns with a smooth transition of blades to a spiral element with a short step. At the same time, the speed of passage is reduced to 12-15 cm/min, increasing the frequency of rotation of the device to the maximum.
Also, during drilling, water can be used, pouring a liquid volume of 10-20 liters for every meter drilled. If the risk of clay accumulation remains, the device must be raised to the surface and thoroughly cleaned after every 1.5-2 meters of drilling. When working with gravel or pebbles, craftsmen choose to increase the screw rotation frequency (approximately up to 300 revolutions per minute).