A well with a casing guarantees the high quality of the foundation of the building, the long life of the foundation and the ability to extract piles during emergency operations. The technology using bored piles with casing makes it possible to complete the initial stage of construction on complex soils in a shorter time. This method is more expensive, but very effective if you need to remove part of the pile or filter from the hole. Arrangement of the foundation and choice casing pipe has its own characteristics.
The technology using BPS and casing allows you to build reliable buildings on complex soils
Content
Varieties of piling
Bored piles are one of the most effective methods for arranging a buried foundation. Its feature is that the wells are drilled to the required elevation, a trunk is formed under the piles with an increase in the lower part and filling of the concrete mixture (soil or sand). The so-called "broadening" of the lower section is formed when drilling soil with special equipment that allows the rock to burst. After this, the concrete is rammed. Sometimes they use a directed explosion at the bottom of the well to seal.
Cylindrical cavities in soils are obtained in a different way, because of which the pile packing is classified into:
- Bored.
- Sandy.
- Soil-concrete.
- Pneumatic
- Frequently rammed.
- Vibrating ram.
Soils “dictate” their conditions for the choice of technology, but today it is possible to build high-rise buildings in almost any environment, thanks to the use of one of them. Experts determine which method will be most effective:
- without strengthening the walls of the well;
- with clay mortar for fastening the drilled trunk;
- using casing products.
The type of installation of piles is determined depending on the type of soil, in many cases, strengthening the drilled trunk is required
Well casing purpose
The use of casing pipes is the formation of wells of various functionalities, including construction, oil production or the extraction of drinking water from deep formations. They are produced by foreign and domestic enterprises in accordance with GOST 632–80.
Casing pipes have a characteristic shape with a prepared joint - for ease of connection. In some cases, welding or joining using special clamps of the clamping type is used. Pipes are produced from different materials, mainly asbestos cement, stainless steel or plastic. Cast iron, wood and some varieties of polymers are used less often - when drilling piles for domestic needs. All of them prevent shedding of soil and siltation of dug wells.
The use of casing pipes for piles - the ability to work in any conditions, and the cylindrical products themselves can be temporarily left in the ground or removed from the holes. These are the so-called "inventory" pipes. Well drilling is carried out using special equipment (percussion or rotational method).
Attention! In industry, only steel and plastic pipes are suitable, which are often given the advantage because of their availability.
Pipes have a different shape and diameter, ovality and difference, an indicator of indirectness (increased accuracy), for which there is a standard:
- products from 33.5 mm to 89 mm - within 0.3 mm;
- products with a diameter of 108 mm to 146 mm - within 0.5 mm;
- in products of larger diameter, an error of more than 0.7 mm is permissible.
When installing bored piles, steel pipes are most often used as casing
Casing asbestos-cement pipes for piles have thick walls, but they are more fragile than the other assortment. They are readily acquired, due to availability, but for inexperienced workers they cause some difficulties in organizing drilling.
Installation of the casing shaft is carried out in stages - each pipe is attached to the previous one. Depending on the technology, pipes are also dismantled in sections in the same way or left in the ground. This should be a corresponding entry in the technical work journal and the acceptance certificate (for each pile).
Mandatory cleaning of the drill hole for piles from crumbling soils upon completion of this stage of work. A special drill or “Kelly bar” is used with the position of the blades having a gripping function.
The advantage of bored pile technology
Casing pipe is a reliable way to strengthen the soil wall in the formed holes. Pipes for bored piles consist of rigidly connected sections. The use of this technology in practice is effective not only on problematic soils, but also when building buildings in megacities on a small area. The speed of mining and the cost of installation depends on the main factors:
- general condition of drilling equipment;
- well diameter and depth;
- type of soil.
The principle of the technology for the construction of bored piles with casing is quite simple. During the formation of deep rods, a drill shaft is formed in stages, with the coupling of the pipes one after another. The tight fixation of the casing (from any material) is important as it moves deeper.
- Drilling equipment is installed at the prepared site, which makes the wells of design width and depth.
- Plastic or metal casing pipes for bored piles are buried by means of a barrel twist. The required level is fixed in advance in the design documentation.
- Fragments of the pipes interlock with each other in the manner that is provided for products made from one or another material, the so-called “leading penetration”.
- When the drill post is fully formed, soil that has crumbled during hole formation is removed.
- In the prepared shaft insert the frame from the reinforcement under the piles.
- The prepared cement-sand mixture is supplied in batches - through a concrete pipe (piling).
- From the well, the casing is removed section by section.
The cement-sand mixture is poured into the prepared well in small portions.
Advantages of safe casing piling technology:
- the ability to work near closely located structures, due to the absence of shock and vibration processes during excavation;
- work in complex soils (floaters, water-saturated, weak and crumbling, salt marshes);
- guarantee of perfect vertical and one hundred percent quality of drilling;
- high performance drilling equipment,
- the possibility of deep work with overlapping horizons;
- safety of pile work;
- one hundred percent protection of downhole mines from collapse and control of all stages of the process;
- protection of the mine shaft from groundwater;
- saving concrete with effective pouring (without necks);
- minimizing the number of miscalculations during installation;
- drilling, broadening, extraction of boulders and large fractions when working with a drill;
- conformity control of design parameters to practical work;
- maximum possible load-bearing functionality of a well due to a high-quality wall.
One type of casing is plastic products. Polymer parts are available for various purposes from such varieties of materials:
- LDPE - high pressure polyethylene;
- HDPE - low pressure polyethylene;
- PNP - low density polyethylene;
- PVC - polyvinyl chloride.
The wall thickness of the casing varies within 40mm. These products have many advantages:
- sufficient tightness of the connection;
- lack of corrosion processes;
- low cost relative to metal products;
- low weight;
- high resistance to chemical or other aggressive environments;
- accelerated installation due to the simple connection of the sections of the casing.
Polymer casing can be used only for the installation of domestic water wells
The only minus is that plastic casing is not very durable, which is why it is easy to destroy their integrity with a sharp blow with a sharp tool and they are not suitable as casing with BNS. They prefer to use these products because of their low cost and practicality for drilling domestic wells for water supply to private households.
Recommendations for work in different soils
In areas with aggressive (natural and industrial) waters, bored technology using this material is often abandoned in favor of asbestos-cement products. Without reinforcing the walls, the drill rod is being worked out in swelling and refractory soils.
In difficult geological conditions, it is difficult to do without the installation of bored piles using casing pipes. It is used on terrain with a high probability of landslides and avalanches, while the casing is not removed. Sometimes it is necessary to strengthen the walls of the well under excess water pressure. In such conditions, experts do not recommend the use of the technology described above.
At the end of the work, the pipe sections are dismantled, but if it is supposed to be designed, they are left in the ground. Sometimes this is required for additional protection of concrete piles from soil movement in difficult geological or seismic conditions.
Product Diameter Selection
Products of different diameters are offered in specialized catalogs for bored piles with casing. These parameters are indicated on the marking and described in the technical documentation (internal and external) diameter. Thanks to this, there is the possibility of the most accurate fitting of pipes for the development of a hole with a drill, in accordance with international standards:
- The outer diameter is marked - from 620 mm to 2500 mm.
- According to the inner diameter - in the range from 640 mm to 2580 millimeters.
Helpful information! It is not necessary to purchase large diameter pipes to increase the productivity of a water well. It cannot give more water than the water supply on the surface can take and squeeze the aquifer underground. The diameter of the pipes must be proportional to the throughput of the well!
The maximum diameter of casing pipes used with bored piles is 2580 mm
Experts recommend that when drilling, raise the drill as often as possible and excavate. Upon completion of drilling, 2-3 days to remove soil slurry and pump out water from the well to form the maximum expansion. This is important for a greater flow of water into the well.
A deep well (up to 15 m) can be made with your own hands by renting equipment using bored piles with casing. You will need a drill, a tripod for stop, a gate for rotation and connecting elements for fixing the pipes.
The same drilling technology is used at the base of the foundation, and the wall is strengthened by the optimal method. If the independent execution of work seems difficult, you can perform part of the work, for example, prepare the site. Entrust the most difficult stages of this technology to specialists.
The prices for this type of work are different everywhere, and the executing company is obliged to submit an estimate or other statements that indicate regional rates. They include the cost of the purchase and delivery of pipes (if they were not already). The prices for the installation of bored piles (using casing technology) should take into account:
- drawing up a project;
- pipe material;
- type of technology;
- depth and width of the well;
- site geology;
- deadlines (urgent or normal process);
- state of the art;
- total workload (number of wells).
Each technology has its limitations and advantages. All the pros and cons must be weighed, deciding on the choice of drilling methods and strengthening the walls. However, in many cases, they prefer technology that involves the use of bored piles with casing. The methods of strengthening the drill stem are successfully used in many regions of the Russian Federation and other countries.
