Buroinjection piles are used, as a rule, to strengthen the foundations of buildings undergoing reconstruction. Their wide use is due to several factors. First of all, the drilling pile piles have small dimensions together with special technical capabilities for use. These designs allow working in rooms whose height is up to two meters, punch holes through reinforced concrete, concrete up to three hundred millimeters in diameter and up to fifty meters deep. A small installation can drill in a room with an externally mounted power unit.
Buroinjectional piles have varieties. One of the types are the structures used in new buildings for reinforcement and fences for vertical slopes. They are called "injection anchors". Special anchor installations are used.
Depending on the ground conditions, a choice is made of one or another tool for drilling. The borehole piles have a length and a diameter in accordance with a given load-bearing capacity of the piles or the force perceived by the anchor.
Drilling in unstable and waterlogged soils is carried out by washing the well with clay mud or using
The device is implemented using reinforcement. In this case, in accordance with the nature of the acting load, the reinforcement is carried out over the entire length or in the upper part. The length of the reinforcement section is determined in accordance with the height of the room. Armocarcas are installed after, before, or during the testing of the well.
The device assumes the presence of fixing components, centering the piles in the wells and providing the necessary thickness of the protective layer in the concrete. With the help of welded joints, the length and, consequently, the strength of the reinforcement are ensured. On the contour of the pile at a distance of at least the diameter of the rod itself are located rods. Usually the cross-sectional area of the longitudinal reinforcement is not less than 0.5% of the cross-sectional area of the pile itself.
To strengthen the bearing characteristics of the pile, due to compaction of the soil, the well walls and freshly applied concrete are pressed.
Crimping can be done in various ways.
Thus, it is possible to pump an additional portion of the solution with a pump through a tampon that is unclamped at the wellhead, in a wellhead or an existing base. In this case, the crimping is performed at a pressure of 0.2-0.3 MPa for two minutes. If the pressure is not maintained during this time, it is not possible to work again, after an hour or two, until the desired result is obtained.
Crimping can also be performed on a certain section of the pile or in the wellbore face through the auger augers.
The work is carried out using electric discharge technology. At the same time, an electrohydrodynamic crimping of the bore hole or walls is performed.
Another method is "repeated injection". In this case, the concrete section is pressed on the pile shaft by injecting the primary infusion of concrete.
Buroinjection piles are arranged in accordance with a certain technological cycle, consisting of several operations:
- Drilling.
- Organization of a reinforced frame.
- Filling the well with a mixture.
- Pressing a fresh mixture.
It should be said that the reinforced frame is allowed to be installed both after and before filling the well with a mixture.
Recently there has been a continuous improvement of the equipment used, technological operations and techniques, which, undoubtedly, is aimed at improving the quality and bearing capacity of the piles.
Buroinjection piles (LSI) is a technology widely used both in industrial and civil engineering. LSI are concrete structures ranging in diameter from 120 to 300 mm and depth of deposit up to 20 meters, made by injection of concrete solution inside the well during drilling.
Fig. 1.1: Stages of creation of drill-in piles
Let's consider the main advantages of drilling pile injection:
- Bearing characteristics of this type of piles in moisture-saturated soil and soils prone to whipping, exceed the characteristics of analogues by an order of magnitude;
- Buroinjectional piles have small dimensions, in comparison with boron-boring designs, but they are not inferior to them in terms of strength characteristics;
- Buroinjection technology for erecting piles does not have a negative impact on the soil and foundations of buildings that have already been erected, such piles can be created in a densely populated city and landslide-prone areas;
- Economical - drilling-injection technology in most cases is realized without the use of casing pipes, which significantly reduces its cost;
- The minimum amount of excavation causes a high rate of erection of the foundation from the drilling pile.
Where the drill piles are used
The device pierreinjection piles resorted to in cases where, due to the nature of the soil, other types of pile foundations can not be used. There are also cases where it is the drilling pile drivers that are the most preferred option.
Fig. 1.2: Strengthening of the foundation of the house by drilling injections piles
We shall understand, in what situations it is better to apply piles of drilling-injection type:
- The need to strengthen already built overloaded foundations (when building premises);
- To strengthen the foundations when changing operational loads of buildings (replacement of production equipment with more dimensional, increasing bridges);
- When erecting buildings in a heavily built area of the city or in construction work in a confined space (in the territory of existing plants and enterprises);
- For correcting the roll of foundations, which arose as a result of their precipitation;
- When building buildings on problematic soil.
Buroinjection piles very often used in the reconstruction of the bases, because the injection technology allows performing the strengthening of the problem foundation without disturbing the structure of the soil on which the building is located and, thus, not exacerbating the emergency situation.
Fig. 1.3: Strengthening of soil with drilling pits
Types of drilling pile injection piles
Classification of drilling pile piles is performed proceeding from the technology from the installation, the consonant of which is allocated:
- LSI without additional casing;
- LSI with well casing;
- LSI with screw coiling.
Boring piles without casing They are used to create foundations in normal soils, which contain a minimum amount of groundwater. BIS without casing have a limitation in the maximum diameter, which can not exceed 180 mm.
Type of solution supply when constructing LSI without casing is chosen based on their diameter - this can be either a gravity feed to an already drilled well, or an injection pipe that fills the bore with concrete immediately after the drill reaches its face. BIS without casing is necessarily strengthened by an armored frame.
In soil with insufficient bearing capacity (moisture saturated and prone to shear soil) is practiced to strengthen wells under LSI casing. Such pipes are a metal sleeve, placed in a drilled hole, inside which a concrete solution is pumped.
Fig. 1.4: Arrangement of boring pile with casing
The method of mounting a BIS with a screw coil differs from that of conventional LSI. Wells for such piles are formed by drilling the ground with a screw-like tip fixed to the injection pipe. On the trunk of the injection pipe there is an armored frame, it is immersed in the ground simultaneously with drilling.
Equipment for the installation of drilling pile injection piles
Speed of foundation of foundations from drilling pile piles directly depends on equipment, which is used to install them
For the installation of BIS are applied mobile drilling rigs with a continuous hollow auger (CFA), simply speaking - an injection tube. Visually, the drill string in CFA installations is similar to that of conventional yamobur - the same spiral blades, but inside this column there is a channel for feeding concrete solution.
The first cycle of work CFA plants is to create a well for the future pile - the soil along the blades of the drill string rises to the top until the required depth of the well is reached. In this case, the injector cavity of the drill string is closed with a plug, which prevents entry into the soil hole.
Further, into the drill string by a pump injected concrete solution and there is a raising of the column with simultaneous filling of the well with concrete. All modern CFA-systems perform the supply of concrete under pressure, as a result of which it is compacted and the pile gets more strength. Then the installation instead of the drill string is mounted vibrator and in a well filled with a well drops reinforcing frame.
Fig. 1.5: The drilling rig for drilling pile injection piles BM-881
Construction company "Bogatyr" has a fleet of modern equipment for drilling the leading wells for drilling pile inlets.
- BM-881 - installation that has a powerful power unit capable of drilling wells under the LSI even in frozen ground;
- KG-12m - our "heavy artillery", equipped with a hinged installation of СО-2 , which can drill wells under piles up to 30 meters deep.
Arrangement of drilling pile injection piles
To create a BIS, a concrete mix based on M400 cement and above is used, with a density of no more than 29%. The ratio of cement sand and water is 1: 1: 0.4 or 1: 2: 0.7. The composition of the solution is added sand of fine fractions, with a size of not more than 1 millimeter.
The actual strength of the concrete of the drilling-injection pile must be at least 15 MPa 7 days after its creation, and not less than 30 MPa after 28 days.
For reinforcement, depending on the size of the BIS and the type of soil, both single reinforcing bars and reinforcing cages can be used. In exceptional situations, steel pipes may be used for reinforcement
Fig. 1.6: Armocarcas for strengthening BIS
The type of reinforcement is determined depending on the characteristics of the soil and the load bearing the pile will experience. The frame can be either uniform along the entire length of the LIS (in unstable soil) or mixed (welded cylindrical frame at the point of maximum bending pressure on the pile, and single reinforcement over the remaining length of the LSI) in normal soils.
Armokarkas is made of hot-rolled reinforcing bars of A5 and A4 classes, the diameter of which for structures of different sizes is determined by the requirements of SNiP 2.02.03-85.
Strengthening of emergency bases by means of BIS must be performed immediately after the discovery of their precipitation, the first signs of which are cracking of walls. Also, reinforcement is an important part of the process of preparing existing facilities for the superstructure.
Fig. 1.7.: Strengthening of the foundation by drilling pits
The process of strengthening the foundation The LSI is performed in several stages:
- Design calculations are carried out and the optimum diameter and depth of the piles are determined;
- The work site is being prepared for work, it is being deployed drilling rig ;
- On the perimeter of the emergency foundation a grillage is created, corresponding to the design calculations; . To order work on piling reinforced concrete piles, leave a bid:
Another interesting technology of strengthening the soil and foundations is the drilling pile piles, which is a kind of traditional bored structures.
By their nature they are referred to hanging piles. Abroad they are called "microspikes". Are used, both in civil and in industrial construction.
Scope of Technology
Most often, the technology of drilling pile piles is used when it is not possible to install pile elements, but these cases the scope of this type of construction is not limited.
Similar piles are used for:
In addition, drilling-injection (LSI) piles are used to strengthen and prevent the destruction of unique natural landscapes. With the help of this technology, preventive works were carried out to preserve the Cretaceous Rock in the Svyatogorsk Lavra (Donetsk region, Ukraine).
Types of drilling pile injection piles
The main difference between this technology and bored piles lies in the way the injection solution (concrete fine-grained or cement-sand mixture) is delivered directly to the slaughter.
Depending on the conditions and properties of the soil, as well as the availability of groundwater, several types of structures can be used:
Some features of the device of injection supports
Piles of this type are made mainly with the use of reinforcing structures, while using different installation technologies:
The injection of the injection solution can be carried out through a hollow auger screw or through a special pipe that can be removed or remain in the thickness of the concrete. From the choice of a certain technology will depend on the final price of drilling piles, when removing technological pipes the construction will cost less.
- Feeding is carried out with the help of concrete pumps, while the pressure of the solution can reach 20-30 atmospheres.
- Injection of concrete must be carried out until the concrete mixture begins to leave the wellhead.
- It should be remembered that the technology volume of injected concrete should be 1.25-2.5 of the volume of the well itself. If the borehole took more than this amount, which happens in the poor condition of its walls in the absence of a casing, it is necessary to allow the mixture to solidify, and after that make the final crimping.
- For injections, solutions of grade P4 (according to workability) are used. Demands are also made for the strength characteristics of concrete. Its composition should ensure, at least seven days after casting, strength not less than 15 MPa, and after four weeks not less than 30 MPa.
Strengthening foundations
The reinforcement of foundations by drilling-injection piles can be carried out by drilling them through the existing structure.
The same technology is used to increase the speed of installation of foundation stone foundation:
- Throughout the perimeter of the foundation, a grillage of the necessary structure is mounted.
- After that directly through it wells of the necessary depth are drilled.
- All further operations are standard - injection, reinforcement, pile press. Particular attention should be paid to the quality of the crimping, the pile's working characteristics largely depend on it.
It is worth remembering that the possibility of using this technology of mounting or reinforcing the foundation can only be determined by special calculations. Therefore, it is not worthwhile to mount it yourself, and even more so to design such constructions.
All work should be performed only by professionals, especially since the execution of work requires the use of special equipment.
Buroinjection structures are a modern legacy of traditional piles. They not only are not inferior to their predecessors in key parameters, but also have a number of unique advantages. The main difference is in the formation of the pile body directly in the well, due to which it is possible to avoid such an unpleasant procedure as piling. A low level of vibration during the construction of the pile field allows the safe use of this technology on unstable soils and in conditions of dense urban development.
Mounting technologies
Several types of installation techniques are used for the drilling pile installation. The most popular methods are those that do not involve the installation of casing pipes - most industry experts consider them to be more economical and efficient.
1. Drilling a well. 2. Extraction of the drill string. 3. Feeding the cement solution. 4. Injection of cement slurry through a special tube.
DDS
At the initial stage, the well is created using a special installation. During the drilling, the walls of the canal are compacted by rock. After reaching the calculated depth, a cement slurry is supplied, and the bit itself rises to the surface. At the final stage, the reinforcing channel is immersed in the concrete mass, giving it additional hardness after hardening.
CFA
This technology It involves the use of a continuous hollow auger that lifts a part of the ground outwards. The remaining stages are similar dDS technology way.
Used equipment
When implementing the above technologies, the following types of special equipment are needed:
- drilling rigs,
- vibrating loaders,
- concrete pumps.
When creating piles using the DDS technique, a spreader is used, which compacts the walls of the channel. Exceptions are only areas with solid rock, for drilling which use the so-called zaburnik. CFA technology involves the operation of a continuous auger, through the hollow channel of which a concrete mixture is fed.
The price of production of buroinjection structures by the specialists of "BurStroyAlliance"
When compiling an estimate for the performance of work on the pile field, the geometrical characteristics of the piles (length, section), parameters of the concrete mix and reinforcing cage, and geological factors are taken into account. The cost of work can be affected by the unpreparedness of the site, the urgency of the work and other circumstances. Anyway, we try to set acceptable prices, which fully correspond to the quality of the work performed. We are waiting for your calls and requests!
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