Pipes

Drilled piles with casing pipe: methods and features of staged installation

July 1, 2020

A borehole with casing guarantees the high quality of the base of the structure, long service life of the foundation and the possibility of removing the pile during emergency work. Technology, which uses drilled piles with casing, which makes it possible to perform the initial stage of construction on difficult soils in a shorter time. This method is more expensive, but very effective, if part of the pile or filter needs to be removed from the hole. Arrangement of the foundation and selection of casing pipes has its own characteristics.

The technology using BNS and casing pipe makes it possible to build reliable buildings on difficult soils

Types of piling

Drilled piles are one of the most effective methods of arranging a buried foundation. Its feature is that wells are drilled to the required mark, a trunk is formed under the piles with an increase in the lower part and filling with concrete mixture (soil or sand). The so-called "expansion" of the lower segment is formed when drilling the soil with special equipment, which allows you to expand the rock. After that, the concrete mixture is compacted. Sometimes they use a directional explosion at the bottom of the well for the purpose of compaction.

Cylindrical cavities in soils are obtained in different ways, which is why pile driving is classified into:

  1. Drilling machines.
  2. Sandy.
  3. Gruntobetonnie.
  4. Pneumatic.
  5. Frequently rammed.
  6. Vibratory rammers.

Soils "dictate their conditions regarding the choice of technology, but today it is possible to build high-rise buildings in almost any conditions, by using one of them. Experts determine, which method will be most effective:

  • without strengthening the walls of the well;
  • with a clay solution for fixing the drilled trunk;
  • with the use of casing products.

The type of pile installation is determined depending on the type of soil, in many cases, strengthening of the drilled trunk is required

Purpose of casing in wells

The use of casing pipes is the formation of wells of various functions, including construction, oil production or extraction of drinking water from deep layers. They are produced by foreign and domestic enterprises for the Guest 632-80.

Casing pipes have a characteristic shape with a prepared joint - for ease of connection. In some cases, welding or docking is used using special clamping type fasteners. Pipes are produced from different materials, mostly it is asbestos cement, stainless steel or plastic. Cast iron is less often used, wood and some types of polymers - when drilling piles for household needs. All of them prevent soil collapse and siltation of dug wells.

The use of casing pipes for piles - the possibility of working 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. Wells are drilled using special equipment (impact or rotary method).

Warning! In industry, only steel and plastic pipes are suitable, which are often preferred due to their affordability.

Pipes have different shapes and diameters, ovality and diversity, non-linearity indicator (high accuracy), for which there is a standard:

  • products from 33,5 mm to 89 mm - no more 0,3 mm;
  • products with a diameter of 108 mm to 146 mm - within 0,5 mm;
  • in products with a larger diameter, the permissible error is greater 0,7 mm.

When installing bored piles, steel pipes are most often used as casing

Asbestos-cement casing pipes for piles have thick walls, but they are more fragile, than other assortment. They are willingly bought, due to availability, but for inexperienced workers, they cause some difficulties when organizing drilling.

Installation of the casing mine is carried out in stages - each pipe is attached to the previous one. Depending on the technology, the pipes are dismantled or left in the ground exactly in sections. There should be a corresponding entry about this in the logbook of technical works and the act of acceptance (for each pile).

Mandatory cleaning of the borehole for piles from fallen soil after completion of this stage of work. A special drill or "Kelly bar" is used with adjustment of the position of the blades, that have a capture function.

The advantage of the technology with the use of bored piles

A casing pipe is a reliable method of strengthening the soil wall formed in the 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 work and the cost of installation depends on the main factors:

  • general condition of the drilling equipment;
  • diameter and depth of the well;
  • type of soils.

The principle of technology for installing bored piles with a casing pipe is quite simple. During the formation of deep cores, a drill shaft is formed step by step with the coupling of pipes one after the other. Tight fixation of casing products is important (of any material) as you move deeper.

  1. Drilling equipment is installed on the prepared site, which makes wells of the design width and depth.
  2. Plastic or metal casing pipes for bored piles are deepened with the help of a screw-in barrel pipe. The required level is fixed in advance in the project documentation.
  3. Fragments of pipes connecting each other in that way, which is provided for products made of one or another material, the so-called "preemptive passage".
  4. When the drill string is fully formed, soil is removed, which fell off during the formation of the hole.
  5. A frame made of reinforcement is inserted into the prepared mine under the piles.
  6. The prepared cement-sand mixture is supplied in portions - through a concrete pipe (pile driving).
  7. The casing is pulled section by section from the well.

A cement-sand mixture is poured into the prepared well in small portions

Advantages of the safe technology of driving bored piles with a casing pipe:

  • the possibility of working near nearby buildings, due to the absence of shock and vibration processes during soil excavation;
  • work in difficult soils (floats, saturated with water, weak and crumbling, salt marshes);
  • a guarantee of perfect verticality and one hundred percent drilling quality;
  • high productivity of drilling equipment,
  • the possibility of deep work with overlapping horizons;
  • safety of welding operations;
  • one hundred percent protection of well shafts from collapse and control of all stages of the process;
  • protection of the borehole from groundwater;
  • saving concrete with efficient pouring (without necks);
  • minimizing the number of miscalculations during installation;
  • destruction, expansion, extraction of boulders and large fractions when working with a drill;
  • control of compliance of design parameters with practical work;
  • maximum possible load-bearing functionality of the well at the expense of a high-quality wall.

One of the types of casing pipes is plastic products. Polymer parts are produced for various purposes from such types of materials:

  • PVD - high-pressure polyethylene;
  • HDPE - low-pressure polyethylene;
  • PNP - low density polyethylene;
  • PVC - polyvinyl chloride.

The wall thickness of casing pipes varies within 40 mm. These products have many advantages:

  • sufficient tightness of the connection;
  • lack of corrosion processes;
  • low cost compared to metal products;
  • light weight;
  • high resistance to chemical or other aggressive environment;
  • accelerated installation due to the simple connection of sections of the casing cylinder.

Polymer casing pipes can be used to install domestic water wells

The only downside is that casing pipes made of plastic are not very strong, which is why it is easy to destroy their integrity with a sharp blow with a sharp tool and they are not suitable as cladding with BNS. These products are better to use due to their low cost and practicality for drilling domestic water supply wells for private households.

Recommendations for working in different soils

On the territory with aggressive (natural and industrial) water from drilling technology using this material is often rejected in favor of asbestos-cement products. Without strengthening the walls, the drill rod is processed in swelling and rigid-plastic soils.

In difficult geological conditions, it is difficult to do without the device of bored piles with the use of casing pipes. It is also used in areas with a high probability of landslides and avalanches, at the same time, the casing pipes are not removed. Sometimes it is necessary to strengthen the walls of the well under excessive water pressure. In such conditions, experts do not recommend using the technology described above.

Upon completion of the work, the pipe sections are dismantled, but if provided by design, then they are left in the soil. Sometimes this is required for additional protection of concrete piles from soil movement in difficult geological or seismic conditions.

Choice of product diameter

Products of various diameters are offered in specialized catalogs for bored piles with casing pipe. These parameters are indicated on the marking and described in the technical documentation (internal and external) diameter. Thanks to this, it is possible to most accurately adjust the pipes for making a hole with a drill, in accordance with international standards:

  1. The outer diameter is marked - within from 620 mm to 2500 mm.
  2. On the inner diameter - within the limits of 640 mm to 2580 millimeters.

Useful Information! It is not necessary to buy pipes of large diameter in order to increase the productivity of the water well. She cannot give more water, than it can be received by a water pipe on the surface and squeezed out of the aquifer underground. The diameter of the pipes should be proportional to the throughput capacity of the well!

The maximum diameter of casing pipes, which are used with bored piles, is 2580 mm

Experts recommend raising the drill as often as possible during drilling and making a soil excavation. Upon completion of drilling 2-3 days to remove soil slurry and pump water from the well, to formalize maximum expansion. This is important for greater inflow of water into the well.

A deep well (to 15 m) you can do it yourself with the help of renting equipment using bored piles with a casing pipe. Drills will be needed, tripod for support, a gate for rotation and connecting elements for fixing pipes.

The same drilling technology is used at the base of the foundation, and strengthening of the wall is carried out by the optimal method. If independent performance of work seems difficult, you can do part of the work, example, prepare the site. The most complex stages of this technology should be entrusted to specialists.

Prices for this type of work are different everywhere, and the executing firm are required to submit an estimate or other reporting, where regional tariffs are indicated. They include the cost of purchasing and delivering the pipes (if they weren't already). Estimates for the installation of bored piles (for casing technology) should take into account:

  • drawing up the project;
  • pipe material;
  • type of technology;
  • depth and width of the well;
  • geology of the site;
  • terms of performance of works (urgent or routine process);
  • state of the art;
  • the total amount of work (the number of wells).

Each technology has its limitations and advantages. All pros and cons must be weighed, making a decision on the choice of drilling methods and wall strengthening. However, in many cases it is technology that is preferred, which involves the use of bored piles with a casing pipe. Drill stem strengthening methods are successfully used in many regions of the Russian Federation and other countries.