Driving piles with a diesel hammer. Technology for driving reinforced concrete piles

1. Product type . An element of a given load-bearing capacity immersed in the ground. The immersion is carried out by a series of vertical blows to the head of the pile.

2. Composition of the process. Delivery of piles to the site; installation of piles on a loading unit; immersion of piles into the ground until design “failure”.

3. Login to the process . Previous work (site) was accepted, trial piles were loaded and tested (to determine the actual length of the pile and the time of its immersion).

Tests are carried out on a fully prepared site or at the bottom mark of the design pit before the start of mass production (or delivery) of piles. During dynamic tests, a pile of designed dimensions is driven with hammer blows until the calculated “failure”. During static tests, the design pile is loaded with real vertical load(s). If the test results are positive, an application is given for the production of design piles in a given quantity (per object). If the results are negative, the designers change the length or cross-section of the pile and conduct new tests.

4. Materials . Prefabricated reinforced concrete piles. The cross-section of the piles is square, 300x300 mm. Tubular piles with a diameter of 400–800 mm are also used. The length of piles at PGS facilities is 5–16 m. In this case, piles 12–16 m long can be composed of two elements, connected during the driving process by working joints (Fig. 3.4).

When constructing bridge supports, tubular shell piles with a diameter of 1200–6000 mm are used. From individual sections 6.0 m long, a pile 20.0–40.0 m long is made during the driving process.

Wooden piles can only be used below the groundwater level (wood does not rot in water). Most of the old buildings in St. Petersburg, including cathedrals and palaces, were built on such larch piles. Currently, wooden piles are practically not used in the construction of industrial and civil structures (IGS).

Steel piles - sheet piling. Steel plates of a special profile, 200–400 mm wide and 6–12 m long. They are used for constructing retaining walls and fastening the walls of deep pits (page 31, Fig. 2.4).

4.1. Technique . To drive piles into the ground, a pile-loading unit (SPU) is used. The SPU is a set of two units – a pile driver and a loader.

Koper includes (Fig. 3.5):

Basic vehicle (1) – tractor, excavator, car, mobile bridge;
- guide boom – to hold the piles in the desired position; for attaching the immersing mechanism (loader - 3);
- auxiliary equipment – winches for lifting the pile and loader; boom pointing systems; welded steel or cast head caps with a set of shock-absorbing pads (hard wood, reinforced rubber) (Fig. 3.6).

Guidance systems provide: placing the pile on a point; vertical alignment; correction of the pile position during the immersion process. They provide:

Tilt of the boom at a certain angle in two planes;
- translational movement of the boom “left-right”, “forward-backward”.

It should be noted that not all pile drivers have a full set of these movements; most have only boom tilt movements, which complicates guidance and reduces the accuracy of driving piles.

Loader– a mechanism that drives a pile into the ground using a force impulse (Fig. 3.8, 3.9). It determines the type of technology.

Rational areas of application of various piledrivers:

Tractor installations - driving piles 5–12 m long with piles arranged in a row (the tractor moves along the row), productivity 20–30 pcs/shift;

Excavator (or based on jib cranes) - driving piles 6–16 m long with a cluster arrangement of piles in foundations for columns; from one site, by turning the boom, he immerses all the piles in one bush and moves on to another cluster of piles. Productivity 15–25 pcs/shift;

Bridge SPUs (rail or tracked) complete with a hammer - driving piles 5–10 m long with a row arrangement of piles or a field (Fig. 3.7). They have a high productivity of 40–70 piles per shift. They can move short distances (from house to house) under their own power. However, due to the high initial costs, such installations are effective only for large volumes of work (more than 1,500 piles). They are used for block development of urban microdistricts.

Hammers that differ in the type of drive are used as loaders: internal combustion (diesel), steam-air and mechanical (suspended) hammers. Steam-air hammers come in single and double action. In single-action hammers, the force of steam or compressed air is used only to lift the impact part, and the working stroke is carried out when it falls on the pile. Double action hammers use steam or compressed air energy to increase impact force. Hammer control can be manual, semi-automatic or automatic.

The main parameter of the hammer is the mass of the impact part, which, depending on the type of soil, determines the maximum possible length of the driven pile.

Diesel rod type hammer(Fig. 3.8, a) includes: a chabot with a piston (2), guide rods (5), an impact part with a cylinder (4) and a piston block, which ends with a hinged support consisting of a spherical heel and a head. The purpose of the hinged support is to provide a central blow to the pile with a slight violation of the alignment of the hammer and the pile. To launch the diesel hammer, the striking part is lifted by the headframe winch to the uppermost position using a grappling grapple (Fig. 3.8, a). After this, the gripper releases the impact part and when it falls, compressed air is formed in the cylinder, as a result of which its temperature increases greatly. At this time, a plunger-type pump supplies fuel to the cylinder and the mixture ignites (Fig. 3.8, b). The gases formed during combustion throw the cylinder to its original position (Fig. 3.8, c), and then the hammer operates automatically until the fuel supply stops. The lifting height of the striking part is adjusted by supplying fuel to the cylinder.

To drive piles, diesel hammers with a striking mass of 600, 1200, 1800 and 2500 kg and a number of blows per minute of 50–100 are used. The lifting height of the impact part of the hammer is 1.0–2.6 m. The advantage of diesel hammers compared to steam-air hammers is that they are more mobile and do not require bulky steam boilers or powerful compressors for their operation. The disadvantage of diesel rod hammers manifests itself when driving piles into soft soils, when it is impossible to ensure its automatic operation, since the high degree of air compression necessary to ignite the fuel mixture is not formed in the combustion chamber.

IN tubular diesel hammer(Fig. 3.9) (with a part mass of 1200, 1800 and 2500 kg, respectively), the cylinder (2) is stationary, and the impact part is the heavy movable piston (4). The cylinder at the bottom ends with a stationary striker, which transmits the blow to the pile through an elastic gasket. The plunger pump supplies fuel to the cylinder. Exhaust gases escape into the atmosphere through the pipe. The operating principle of a tubular diesel hammer is the same as a rod hammer.

Tubular diesel hammers are more reliable in operation and have 1.2–0.5 times greater driving capacity than rod diesel hammers.

The disadvantage of these hammers is that they are difficult to start in sub-zero temperatures.

Mechanical hammer used for small volumes of work. It consists of a striking part weighing 1000–3000 kg and a gripping device. After the winch placed on the pile driver raises the impact part of the hammer to the required height, the gripping device releases it and the pile is struck during free fall. Mechanical hammers are inexpensive, durable and have a simple design.

Their disadvantage is that they produce a small number of blows - 3-4 per minute; with constant fastening of the rope to the striking part of the hammer, the number of blows can be increased to 10-12 per minute, but this leads to intense wear of the winch and piledriver.

IN double-action steam-air hammer The impact part during the working stroke is under the influence of gravity and steam or compressed air pressure. Thanks to this, the speed of movement of the striking part is much higher and the number of beats per minute has increased to 20.

The advantage of these hammers is their high driving ability (they can drive piles up to 20–25 m long), but the disadvantage is the bulky and heavy steam power equipment. At industrial and civil construction sites, double-action steam-air hammers are practically not used.

Process composition:

Layout of pile row axes;
- Laying out and securing pile points with pins;
- Placing the unit on a point and placing a pile on it;
- Pointing the pile to the design point using a unit;
- Diving with verticality control and failure measurement;
- When the pile reaches “failure”, immersion stops regardless of the actual depth of immersion of the pile.

« Refusal" - the amount of immersion of the pile from one blow from a series of 10 blows in mm (1.5–4.0 mm), upon reaching which the design load-bearing capacity of the pile is fully ensured.

The piles delivered from the factory are stored on the edge of the pit or laid out at the immersion site (Fig. 3.10).

The pile points are secured in the quantity required “per change” using steel pins with a diameter of 12–16 mm and a length of 300–400 mm. The pile is dragged to the pile driver by a rope through the working block (Fig. 3.11, a) or through the outlet block (Fig. 3.11, b) at distances of more than 15.0 m.

After placing the pile on the SPU, horizontal and vertical alignment, the hammer is launched. To a depth of 1.5–3.0 m, immersion is carried out with weak hammer blows when the striking part is dropped from half the height. Then the plunge is carried out during normal operation of the hammer. The verticality of the pile is continuously monitored in two directions. When it is visually noticeable that the sinking rate is approaching the calculated “failure”, monitoring devices are installed - failure meters, by which the magnitude of the actual failure of the pile is determined.

When driving piles, a “Journal of Piling Works” is kept, in which all piles must be numbered in accordance with the working drawing. For each pile the following is indicated: the amount of “failure”; dive time; immersion depth, as well as special circumstances (“rest”, cracks, fracture, backup pile, etc.).

After reaching the “failure” of the pile, the SPU moves to the next pile point. The underloaded part of the pile (“butts”) is subsequently cut off.

During the driving of piles, cases often arise when the pile does not reach the design “failure” when driven to its full length. In these cases, the following actions are recommended:

One pile did not receive a “refusal”, and the following piles give a “refusal”. The driving of the piles continues, and a backup pile is driven next to the defective pile;

2–5 piles in a row do not give a “failure”. In this case, it is necessary to stop further immersion of piles. After the piles have “rested” (3–7 days), control finishing is carried out. As a rule, in clayey soils the phenomenon of pile “sucking” manifests itself and usually control finishing gives values less than the calculated “failure”;

After the control finishing of a group of piles, the calculated “failure” was not obtained. Work on driving piles is suspended, representatives of the design organization are called to clarify the dimensions of the piles (usually the length of the pile increases).

Delivery of the pile field. Upon delivery the following must be presented:

Certificates for immersion of backup piles; to replace types of piles;
- act of driving and testing test piles;
- as-built diagram of loaded piles;
- passports for piles;
- acts for the installation of joints (for composite piles);
- log of pile work (indicating the failure of each pile).

Cutting off pile heads. To install a grillage, it is necessary to ensure the design elevation of the top of the piles. This is ensured by cutting off the pile heads to the required size. The cutting process is quite labor-intensive. The difficulty lies in the fact that it is necessary to cut two different materials: stone (concrete) and steel (reinforcement), which requires different technologies and cutting tools.

Currently, cutting of pile heads is carried out mainly manually using pneumatic and electric hammers. To reduce the volume of concrete chipping (Fig. 3.13), a steel crimping frame is used. Reinforcing bars are cut by fire or by cutting machines.

Mechanical methods for cutting pile heads are used to a limited extent:

– force chipping with hydraulic jacks (Fig. 3.14, a, b);
– cutting with a circular saw;
– bending of the pile head using special equipment based on a tractor (Fig. 3.14, c).

Currently, thermal, explosive, and cryogenic technologies for cutting off pile heads are also being developed.

Advantages of impact pile driving technology:

High performance;
- driving piles into almost any type of soil;
- a significant increase in the load-bearing capacity of the pile (by 15–30%) due to compaction of the soil under the tip.

Flaws:

Dynamic impact on the pile (there must be a safety margin);
- large dynamic impacts on buildings and structures located nearby.

If there are dilapidated or unsafe buildings near the construction site, this technology is unacceptable.

Source: Technology of construction processes. Snarsky V.I.

Our company carries out work on driving and driving piles in small and medium volumes using high-speed equipment. You can find out in more detail when the use of pile driving machines is justified. Call us and we will help you with driving piles. And now we will talk about diesel hammers, which are used on piling equipment, including our piling equipment.

Types of diesel hammers for driving piles

The classification of impact equipment used in piling work is carried out based on its design features, according to which diesel hammers of the tubular and rod type are distinguished.

Rod-type structures use two vertical rods as a guiding element for the striking part of the hammer, while tubular units use a fixed pipe.

Piling hammers are also divided into groups based on the mass of the impact part. Hammers with a hammer weight are distinguished:

up to 0.6 tons - light;
up to 1.8 tone - medium;
over 2.5 tons - heavy.

Let's take a closer look at each type of diesel hammer.

1. Rod.

You can see rod-type devices in image 1.1:

Rice. 1.1

The design of a diesel rod hammer consists of the following main elements:

Piston block mounted on a hinged support;
Two vertical guide rods;
Fuel mixture supply system;
A device for fixing a pile column is a “cat”.

The piston block is a monolithic structure cast inside the hammer body. It includes the piston itself and compression rings, a fuel supply hose, a nozzle for spraying the fuel mixture and a pump that drives it.

The piston block is fixedly fixed on a hinged support, from the bottom wall of which two guide rods extend.

Rice. 1.2

The rods, for more rigid fixation, are connected at the top by a traverse. During operation, the impact part of the hammer moves along the guide rods, on the lower wall of which there is a chamber for combustion of the fuel mixture.

2. Tubular.

Tubular-type structures are shown in Image 1.3.

Rice. 1.3

The structure of all tubular type hammers is completely unified; they are designed according to established standards and have identical design features.

The tubular diesel hammer consists of the following parts:

“Cats” - for capturing and fastening a pile post, the cat has an automatic locking and releasing mechanism;
Impact striker - it is represented by a piston equipped with compression rings;
Chabot - the striking surface with which the striker comes into contact during the operation of the hammer;
The working cylinder, inside of which there is fuel detonation;
Lubrication and cooling systems;
Guide pipe made of high-strength steel.

Rice. 1.4

Unlike rod-type hammers, tubular structures have a forced water cooling system, which makes it possible to continuously operate these devices, while the operation of rod hammers must include regular breaks after every hour of driving piles, necessary for natural cooling of structural elements.

You can choose the one you need piling installation in our equipment section.

Technical characteristics of diesel hammers

Tubular diesel hammers are rightfully considered the most advanced and efficient designs. With the same hammer weight, they are capable of driving heavier piles (two to three times the difference in the weight of the pile column).

The hammer consists of the following parts:

cylinder (or rods)
baba (impact part, striker) moving inside the cylinder
chabot (the lower part of the hammer to which the head is attached)

The spherical recesses on the baba and the chabot, when in contact, form a combustion chamber. Diesel fuel is supplied into it using the injection method, which, when the woman hits the shaft, under the high pressure created in the combustion chamber, self-ignites and throws the woman to the top point. After which the woman’s fall resumes.

Thus, the hammer makes a series of blows on the pile, plunging it into the ground; the process can be clearly seen in video:

The disadvantages of rod structures also include low durability (the service life, on average, is almost two times less than the service life of tubular hammers).

Diesel rod hammers, due to the limited impact energy, which is 27-30% of the potential energy that the impact hammer can develop, are used exclusively for driving pile pillars into weak, low-density soil.

The most common diesel rod hammers have a hammer weight of 2500 and 3000 kilograms; such designs are capable of delivering impact energy up to 43 kJ, while the number of blows per minute is limited to 50-55. We have this technology: Pile driving equipment.

Rice. 1.5

Tubular type diesel hammers are used for driving reinforced concrete piles into any type of soil. If it is necessary to work in permafrost soil conditions, pre-drilled leader wells are used for driving piles.

Operating temperature range tubular piling hammers vary from -45 to +45 degrees. If piling work is carried out at temperatures below 25 degrees, additional heating of the piston block is required before starting the hammer.

Striker weight in tubular diesel hammers it can be 1.25, 1.8, 2.5, 3.5 and 5 tons. The firing pin, depending on its weight, can develop an impact force from 40 to 165 kJ. The maximum number of hammer blows per minute of work is 42.

Technology for driving piles with a diesel hammer

A diesel hammer is a specific piling equipment that is hung on the mast of a piling machine, that is, it is a mounted piling mechanism. The principle of operation of a pile hammer is to strike the pile using the force of its own weight.

The specifics of pile driving technology will vary depending on the type of equipment used.

Let's consider the main stages of driving piles with a diesel rod hammer:

Upon completion of slinging and fixing the pile, the “cat”, fixed on the headframe winch, lowers down and engages with the impact part of the hammer;
The cat and the firing pin are raised using a winch along the guides to the maximum upper position;
The operator activates the release lever and the striking part, under its own weight, falls down to the hinged head mounted on the pile post;
During the process of lowering the striker, the air inside the cylinder is compressed and increases its temperature (up to 650 degrees);
When the impact striker comes into contact with the hinged head of the pile, fuel is pumped into the cylinder by a nozzle, which is mixed with compressed air;
Upon impact, self-ignition of the fuel mixture occurs; the gas released as a result of detonation pushes the striker to the upper starting position;
During the lifting process, the speed of movement under the weight of the striker decreases, and the striker lowers back to the hinged head attached to the pile post. The process is repeated until the pile driver operator turns off the fuel pump.

Rice. 1.6

The sequence of operation of a tubular hammer when driving piles is as follows:

The piston part is connected to the cat and raised to the upper position using a headframe winch;
The piston and cathode are automatically uncoupled and the striking part is lowered along the guide pipe;
As the piston falls, the pump is activated, which pumps fuel into a special recess located on the upper wall of the chabot body;
As the piston is further lowered, the air inside the hammer tube is compressed;
When the piston hits the shaft, the fuel mixture detonates, half of the energy goes to immersion of the pile column, and another part goes to throwing the piston to its original position.

Rice. 1.7

The immersion of the pile column is carried out as a result of the influence of two types of energy - shock (emanating from the mass of the striker) and gas-dynamic, which is released at the moment of detonation of the fuel mixture.

Our company will supply equipment to the site

The Bogatyr company carries out piling work in strict accordance with the requirements of SNiP and other regulatory documents.

The technology for driving piles is fully described in documents specially developed for the period of piling work: PPR (works project), technological map, etc., during the work a summary sheet of pile driving is maintained. Thus, the process in the full sense is production and its strict execution, especially during pile driving, is monitored by the person responsible for the piling work.

Driven piles are driven into the ground by impact, vibration, indentation, and a combination of these methods.

At a construction site, pile storage areas should be located closer to the pile driver paths so that the piles can be lifted with a pile driver without a crane. The movement of the piledriver should be as straight as possible with a minimum number of turns.

The most widely used method is the impact method of driving piles. According to this method, various hammers are used to drive piles - mechanical, steam-air and diesel hammers, which are mounted on pile drivers or mobile pile drivers.

The process of driving a pile consists of the following operations: moving the pile driving unit to the place where the pile is being driven, pulling, lifting, aligning and installing the pile, and then driving to the design mark or specified failure.

For large volumes of piling work and the use of piles longer than 12 m, universal tower-type pile drivers are used, mounted on trolley platforms moved on rails. Such copra have a large load capacity and significant dead weight.

The most widespread in industrial and civil construction are self-propelled pile driving installations based on cranes, excavators, tractors and cars.

Such installations have greater maneuverability and are used for driving piles 3-10 m long. Pile driving installations allow you to drag and lift the pile, and insert the head of the pile into the cap.

The efficiency of driving a pile depends on the correct choice of a pile hammer, namely on the correct determination of the ratio of its mass and the mass of the pile. This also takes into account the type of soil into which the pile is immersed. The mass of the impact part of a free-falling hammer when driving a 12 m long pile into dense soils should be equal to 1.5 of the mass of the pile with a cap, and when driving into medium-density soils 1.25 of this mass.

Steam-air hammers come in single and double action.

In single-action hammers, the drive energy (steam or compressed air) is used only to lift the impact part, and its fall occurs under the influence of its own mass. In double-action hammers, the drive energy also goes to the downward movement of the striking part, increasing its speed and, consequently, the impact force: pa. Single-action hammers have a hammer mass of 1.25-6 tons, the number of blows does not exceed 30 blows per minute. Most double-action steam-air hammers have a piston as their striking part. The number of hammer blows per minute can be more than 200 and can be adjusted automatically. Using double-action hammers, piles are driven in vertical and inclined positions.

Diesel hammers come in tubular and rod types. The impact part of rod hammers is a movable cylinder, open at the bottom and moving in guide rods. When the cylinder falls onto a stationary piston, a mixture of air and fuel ignites in the combustion chamber. The energy generated as a result of the combustion of the mixture throws the cylinder upward, after which a new blow occurs and the cycle repeats. The fuel enters the combustion chamber injector through a tube passing through the piston block using a high-pressure pump, which is driven by a movable cylinder.

For tubular diesel hammers, a fixed cylinder with a top is a guide structure. The impact part of the hammer is a movable piston with a head. Fuel atomization and ignition of the mixture occurs when the piston head hits the surface of the spherical cavity of the cylinder, where fuel is supplied by a low-pressure pump.

The number of blows per minute for rod diesel hammers is 50-60, for tubular ones 47-55.

Tubular diesel hammers, compared to rod hammers, with the same mass of the impact part, have significantly greater (2-3 times) impact energy. For driving piles 8-10 m long, it is recommended to take the following ratio of the mass of the impact part of the hammer to the mass of the pile: for rod hammers - 1.25: for tubular diesel hammers 0.5-0.7.

In winter, rod diesel hammers can be started at a temperature of -30 ° C, and to start tubular diesel hammers already at temperatures down to -20 ° C, it is necessary to use special fuel additives and preheat the hammer for 20-30 minutes. Rod hammers operate more steadily in winter conditions.

The caps allow you to secure the pile in the guides of the pile driving machine and protect the pile heads from destruction during hammer blows. When driving piles with overhead and steam-air hammers, cast and welded metal caps with shock-absorbing pads made of hardwood or polymer materials are used. The head cap is hung from the hammer by the ears and together with it is raised and lowered onto the pile. For diesel hammers, caps with a rotating frame are used, which allow the head of a pile lying on the ground to be inserted into the internal cavity when the hammer is lowered. After moving the pile driver to the required position, it is centered along the axis of the pile being driven. Verify the verticality of the booms in two planes, and for driving inclined piles, set the specified angles of inclination of the booms. After this, the pile driver is secured with tension brackets or outriggers, the hammer is raised and secured in the upper position. Using a rope and remote blocks, the pile is pulled up, lifted and installed at the immersion site. The upper end of the pile is brought under the head and the hammer is lowered.

After installing the pile on the ground and aligning it, the hammer is slowly lowered onto the head and, under the influence of the weight of the hammer, the pointed end of the pile is pressed into the ground. To ensure the correct direction of the pile, the first blows are performed from a small height (no more than 0.4-0.5 m). When using diesel hammers, measure the operating time of the hammer for each meter of pile penetration and the number of blows per minute. It is important at the beginning of driving the pile to ensure that the pile is driven correctly horizontally and vertically or at a given angle of inclination. Inclined piles are driven using pile-driving machines, the guide masts of which can be installed with a slope. The mast is installed according to the tilt indicator, which has a graduated scale.

At the end of driving with the help of mechanical and steam-air hammers of single action, when the pile is driven approximately to the design mark or to design failure, driving is carried out with “collaterals” of 10 blows each. When driving piles with double-action hammers and diesel hammers, it is difficult to count the blows, so the amount of penetration is measured in 1 minute.

When using self-propelled piling machines, the duration of the main operations (driving piles) is only 40% of the time, and the rest of the time is spent on auxiliary operations. When using non-self-propelled pile drivers and performing piling work in winter, auxiliary operations occupy 70-80% of the total time spent on driving the pile. Thus, mechanization of support operations is important for increasing labor productivity.

With the vibration method, the pile is driven using vibration machines, the dynamic effect of which allows one to overcome the soil resistance along the side surface and under the tip of the pile.

Vibrating machines are used as vibrating machines, which are suspended from the mast of the pile-loading installation and connected to the pile by the head.

The amplitude of vibrations and the mass of the vibration system (vibration driver, cap and pile) must ensure destruction of the soil structure with irreversible deformations.

Vibratory hammers are divided into high-frequency (700-1500 min-1) and low-frequency (300-500 min-1).

High-frequency ones are designed for driving light piles into soils that do not offer much resistance, for example, water-saturated sandy and weak plastic silty-clay soils.

Low-frequency loaders are used when driving heavy reinforced concrete piles and shells with a diameter of more than 1000 mm. The choice of vibratory hammers should be made based on the load-bearing capacity of the pile and soil conditions.

For low-frequency vibration submersibles, the required driving force, kN, is determined by the formula

Vibratory loading of piles at the beginning should be carried out at a low speed of lowering the vibratory driver, without slack in the rope, but also without strong tension. This prevents the possibility of deflection of the pile during the initial period of immersion.

The vibration method is most effective when driving piles into non-cohesive soils. To drive piles into low-moisture, dense, dusty, clayey soils, it is necessary to construct leading wells using drilling mechanisms. More universal is the vibroimpact method of driving piles using vibratory hammers, which, based on the type of drive, are divided into electric, pneumatic, hydraulic and vibratory hammers with internal combustion engines.

The most common spring vibratory hammers work as follows. When the unbalances rotate in opposite directions, the vibration exciter performs periodic oscillations. When the gap between the vibration exciter hammer and the anvil of the pile cap is less than the vibration amplitude of the vibration exciter, the hammer periodically strikes the pile cap anvil. For more efficient driving of the pile, the mass of the impact part of the vibratory hammer must be at least 50% of the mass of the pile and be 650-1350 kg.

Static indentation of piles is carried out by transferring increased mass to the pile, and with vibration indentation simultaneously with the action of vibration. To drive piles using the static indentation method, installations consisting of two tractors, a guide frame and a base plate are used.

The process of pressing piles is as follows. A tractor with a mast is installed above the place where the piles are immersed and, using a winch, the base plate is lowered to the surface of the ground, on which the loading tractor is then installed. The pile is first winched into the opening of the tractor mast located on the ground. The forces from the winch are transferred to the head and it begins to move along the guides, pressing the pile into the ground.

The installation develops a pressing force of up to 350 kN and can load 10-15 piles up to 6 m long per shift. The accuracy of pile driving is ensured by the construction of leading wells. The disadvantages of this method are low productivity, bulky equipment, which reduces maneuverability, and a small depth of immersion of piles.

More effective is the pressing of piles using vibration-pressing installations, when the pile is immersed from the combined effects of vibration and static load. On the rear frame of the vibration-pressing installation there is an electric generator powered by the tractor engine and a double-drum winch. On the front frame there is a guide boom with a vibrating loader and blocks through which the pressing rope from the winch passes. After installing the pile and turning on the vibratory driver, the pile is immersed in the ground due to the influence of vibration, as well as due to its own weight, the mass of the vibratory driver and part of the tractor mass transmitted by the pressing rope through the vibratory driver to the pile.

Vibration is generated by a low-frequency loader with a sprung plate.

To reduce resistance in dense soils, piles are driven using undermining. Water is supplied under pressure of at least 0.5 MPa through tubes with a diameter of 38-62 mm, mounted on a pile. The arrangement of the tubes can be lateral or central, when one single-jet or multi-jet tip is placed in the center of the driven pile. With lateral erosion, more favorable conditions are created to reduce friction forces on the side surface of the pile. As a result of undermining, the pile is immersed under the influence of its own weight and the weight of the hammer or vibratory driver installed on it. If the pile itself does not sink, it is driven in with light hammer blows or vibration without stopping the washing. When undermining, the adhesion of the soil under the tip and along the side surface of the pile is disrupted, which reduces its load-bearing capacity. Therefore, the pile is immersed in the last 1-2 m without undermining. Additional operations for driving piles with undermining lead to an increase in labor intensity and cost of work, and therefore this method is used quite rarely, mainly when driving heavy piles more than 8 m in length and shells.

When driving composite piles, it is necessary to join the piles during the driving process.

In our country, new designs of driven piles have been developed, which are used in some soil conditions.

In soft soils, club-shaped piles are used. Such piles were used in the construction of the hydraulic ash removal route for the Krasnogradskaya Thermal Power Plant in a wetland as foundations for pipeline supports.

Self-expanding gantry piles are elements that are not connected to each other and have beveled lower ends. For. When such piles are immersed in the ground, the piles are placed next to each other with bevels inward. As the piles sink, their lower ends diverge due to the impact of the reactive forces of the soil on the bevels, as well as on the lateral internal surfaces of the expanding piles.

The nature of the work of self-expanding piles when inserted into the ground differs significantly from the work of conventional inclined piles, since during immersion each branch of the pile performs a complex movement, moving progressively downward and turning relative to the hinge of the head.

In dense sandy and silty clay soils with a fluidity index /L<;0,1 не рекомендуется применять самораскрывающиеся сваи из-за больших изгибающих моментов, возникающих при погружении таких свай в грунт.

When driving piles into seasonally frozen soils, it is necessary to perform additional operations to ensure that the piles are driven to the design level. If the freezing depth does not exceed 0.5-0.7 m, then using powerful hammers it is possible to break the piles through the frozen soil layer. Sometimes, to prevent freezing, the places where piles are driven are insulated in advance with sawdust and straw. If it was not possible to prevent freezing, then the frozen layer is drilled with leading wells, destroyed with vibrating impact installations or destroyed by other mechanical means, and the frozen soil is also thawed. The soil is heated by fire using thermal drills with jet burners or thermochemically. Deep electrical heating of the soil is also used. Sometimes thermal electric heaters (TEHs) are used.

pile storage areas should be located closer to the movement paths of the pile drivers so that the capture and lifting of the pile can be done from the pile drivers;

the movement of the pile driver should be as straight as possible with a minimum number of turns and minimum idle passes;

Where possible, vehicles inside the construction site should move in a circular pattern.

The PPR for pile work should include the following materials: characteristics of pile foundations, their volume and layout of piles on the pile field, technological calculations, technological maps, contents of the work flow diagram, work schedules or schedules.

The order of driving piles is determined by the PPR and, as a rule, depends on the equipment used for driving piles and the design location of the piles.

When piles are arranged in a straight line in separate rows or in bushes, the row pile driving system is most widely used. The spiral system involves driving piles in concentric rows from the edges to the center of the pile field. With a complex arrangement of piles and large distances between them, the driving order is determined by considerations of efficient use of equipment. When choosing the order of driving piles, it is necessary to take into account the possibility of reducing the duration of operations for pulling piles.

The choice of pile driving method is influenced by the following factors: physical and mechanical properties of the soil, type of piles used, driving depth, tightness of the construction site, design features and productivity of the equipment used, as well as the volume of piling work. The weight, length and design of the pile have a significant impact on the choice of pile-loading equipment.

Pile-loading installations must have low weight, maximum maneuverability, ease of installation, dismantling and maintenance.

Driven piles are made on the surface of the ground and then driven into the ground in a vertical or inclined position. There are several methods for driving driven piles.

Impact method. This method is based on the use of impact energy, under the influence of which the lower end (pointed part) of the pile is embedded into the ground. As it sinks, it displaces soil particles to the sides, partly down and partly up. As a result of immersion, the pile displaces the volume of soil and thus further compacts the soil base. The impact load on the pile head is created by special equipment. mechanisms - hammers of various types, the main one being diesel. As a rule, rod and tubular diesel hammers are usually used.

The process of driving a pile consists of the following operations:

pulling and lifting the pile while simultaneously inserting its head into the head socket in the lower part of the hammer;

installation of the pile in the guides at the driving site;

driving the pile first with several light blows and then increasing the force of the blows to maximum. If the position of the pile deviates from the vertical by more than 1%, the pile is straightened with supports, ties, etc., or removed and driven in again;

moving the pile driver and cutting the pile at a given mark.

Pile driving is carried out until the failure specified by the project is achieved.

Refusal- depth of immersion of the pile from one blow. Failure is measured to the nearest 1 mm. The settlement from a single blow at the end of driving a pile is difficult to measure, so failure is defined as the average value over a series of blows, called a pile.

When driving piles with diesel hammers and single-action steam-air hammers, the deposit is taken equal to 10 blows; when driving piles with double-action hammers and vibratory hammers, the deposit is taken equal to the number of blows per 1 minute of driving.

If the average failure in the 3 subsequent pledges does not exceed the calculated value, then the pile driving process can be considered complete. Piles that did not give a control failure after a break lasting 3-4 days are subject to control driving; if the depth of immersion of the piles has not reached 85% of the design one, and during the last 3 pledges a design failure was received, then the reasons for this phenomenon must be identified and agreed with design organization.

Vibration method. The method is based on a significant reduction in vibration of the coefficient of internal friction in the soil and the friction force of the side surfaces of piles. Thanks to this, when vibrating and driving piles, tens of times less effort is required than when driving. In this case, partial compaction of the soil is observed. The compaction zone is 1.5-3 pile diameters, depending on the type of soil and its density. With the vibration method, the pile is driven using special mechanisms - vibratory drivers. The vibratory driver is suspended from the mast of the pile of the driving installation and connected to the pile with a cap. The action of the vibration suppressor is based on the principle in which horizontal centrifugal forces are mutually compensated, and vertical ones are summed up.

The amplitude of vibrations and the mass of the vibration system (vibrating hammer, cap, pile) must ensure destruction of the soil structure with irreversible deformations. During vibration immersion in clay or heavy loam, a clay cushion is formed under the lower end of the pile, which causes a significant reduction in the load-bearing capacity of the pile. To eliminate this phenomenon, the pile is driven by impact to a length of 15-20 cm. To drive light piles (up to 3 tons) and metal sheet piles into soils that do not provide high drag under the tip of the pile, high-quality vibratory drivers with sprung loading are used.

The vibration method is most effective for non-cohesive, water-saturated soils. the use of the vibration method for driving piles into low-moisture dense soils is possible only when constructing leading wells.

Vibro-impact method driving piles - universal. The vibratory hammer strikes the pile cap when the gap between the vibration exciter drummer and the pile is less than the exciter oscillation amplitude.

The mass of the impact part of a vibratory hammer for reinforced concrete piles must be at least 50% of the mass of the pile and is about 650-1350 kg.

Indentation method (static method) short piles (up to 6 m) are safer for surrounding structures than vibration and vibration-impact methods. However, in dense soils, it is necessary to drill leading holes of small diameter before pressing.

Vibration pressing. During vibration indentation, the pile sinks from the combined effects of vibration and static load. This method is more effective than simple pressing.

The vibration-pressing installation consists of 2 frames; on the rear frame there are electric generators powered by a tractor and a 2-drum winch. On the front frame there is a guide boom with a vibrating driver. When the vibratory-pressing installation reaches its working position, the vibratory driver is lowered down, the pile is connected with a cap and lifted to the place of driving.

The vibration pressing method eliminates the destruction of piles and is effective when driving piles up to 6 m long.

Screwing. Screw piles are made of steel or combined: the lower screw part is steel; the top is reinforced concrete. Such piles are used as foundations and anchors in the construction of masts, power lines, radio communications, etc.

The work operations when driving a pile using the screwing method are similar to those performed when driving piles using the driving or vibration method, only instead of installing and removing the cap, shells are put on here.

Method with soil washing. With underwater pressure of at least 0.5 MPa, rack piles can be immersed if there is no danger of settlement of nearby structures. The location of the flushing tubes can be central or lateral. The central location is more preferable, since when positioned laterally, the flushing tubes are often damaged and filled with soil. Due to erosion of the soil under the heel of the pile, 1...1.5 m before the design mark, the erosion is stopped, and then the pile is immersed without erosion.

Electroosmosis used when driving piles into dense clay soils. After a short-term exposure to direct current, groundwater collects near the walls of the submerged cathode pile, reducing the friction forces between the pile and the soil

a - vibration; b - vibration shock; c - indentation; d – vibration compression;

d - screwing; e - washing; g - electroosmosis.

From construction industry enterprises or from supply bases of construction organizations, reinforced concrete and wooden piles, steel pipes and sheet piles are delivered to the work site in a prepared form.

Piles are driven by impact, vibration, indentation, screwing, using washing and electroosmosis, as well as combinations of these methods. The effectiveness of using a particular method depends mainly on pound conditions.

Impact method

The method is based on the use of impact energy (impact loading), under the influence of which the pile is embedded in the pound with its lower pointed part. As it fuses, it displaces the particles of the pound to the sides, partly down, partly up (to the surface). As a result of deflation, the pile displaces a volume of pound almost equal to the volume of its vented part, and thus further compacts the pound base. The zone of noticeable compaction around the pile extends in a plane normal to the longitudinal axis of the pile over a distance equal to 2...3 times the diameter of the pile.

Impact loading on the pile head is created using special mechanisms - hammers of various types, the main ones being diesel ones.

Rod and tubular diesel hammers are used on construction sites.

The impact part of diesel rod hammers is a movable cylinder, open at the bottom and moving in guide rods. When the cylinder falls onto a stationary piston in the combustion chamber of the mixture, the energy throws the cylinder up, after which a new blow occurs and the cycle repeats.

In tubular diesel hammers, a stationary cylinder with a chabot (heel) is a guiding structure. The impact part of the hammer is a movable piston with a head. Fuel atomization and ignition of the mixture occurs when the piston head hits the surface of the spherical cavity of the cylinder, where the fuel is supplied. The number of blows per 1 minute for rod diesel hammers is 50...60, for tubular ones - 47...55.

The main indicator characterizing the plunging ability of a hammer is the energy of one blow. The latter depends on the weight and height of the fall of the impact part, as well as the energy of fuel combustion. Impact energy values (kJ) can be quantified using the following expressions:

for rod hammers

for tubular hammers

where Q is the weight of the impact part of the hammer, N, h is the height of the fall of the impact part of the hammer, m.

For specific construction conditions, the hammer is selected according to the required nominal energy of one blow and the hammer applicability factor.

Required rated impact energy

Based on the obtained value En, a hammer is selected (according to the relevant reference books), and then it is checked according to the coefficient of applicability of the hammer k, which is determined from the ratio of the weight of the hammer and pile to the impact energy, i.e.

K = (Q1 + q) / En,

where Q is the dead weight of the hammer, N, q is the weight of the pile (including the weight of the head and headstock), N.

The k value ranges from 3.5 to 6 (depending on the pile material and the type of hammer). For example, for driving reinforced concrete piles with a diesel pile hammer k = 5, wooden piles k = 3.5, and tubular piles - k = 6 and L = 5, respectively.

The hammer kit usually includes a head cap, which is necessary to secure the pile in the guides of the pile-driving installation, protect the head of the pile from destruction by hammer blows and distribute the impact evenly over the area of the pile.

The internal cavity of the cap must correspond to the shape and size of the pile head.

To drive piles in order to hold the hammer in working position, lift and install the pile in a given position, special lifting devices are used - pile drivers. The main part of the piledriver is its boom, along which the hammer is installed before diving and lowered as it is driven. Inclined piles are driven using tilting boom pile drivers. There are rail-mounted pile drivers (universal metal tower-type ones) and self-propelled ones - based on cranes, tractors, cars and excavators.

Universal pile drivers have a significant dead weight (together with the winch - up to 20 tons). The installation and dismantling of these pile drivers and the construction of rail tracks for them are very labor-intensive processes, so they are used for driving piles more than 12 m long with a large volume of piling work on site.

The most common piles in industrial and civil construction are 6...10 m long, which are driven using self-propelled pile driving units. These pile-driving installations are maneuverable and have devices that mechanize the process of pulling and lifting the pile, installing the pile head into the cap, and also aligning the boom.

Driving piles begins by slowly lowering the hammer onto the cap after setting the pile on the pound and aligning it. The weight of the hammer forces the pile into the pound. To ensure the correct direction of the pile, the first blows are made with limited impact energy. Then the hammer impact energy is gradually increased to maximum. Each blow causes the pile to shrink by a certain amount, which decreases as it deepens. Subsequently, a moment comes when, after each pledge, the pile is reduced by the same amount, called failure.

The piles are driven until the design failure specified in the project is achieved. Failure measurements should be made with an accuracy of 1 mm. The failure is usually found as an average value after measuring the immersion of the pile from a series of impacts, called the deposit. When driving piles with single-action steam-air hammers or diesel hammers, the deposit is taken equal to 10 blows, and when driving with double-action hammers - the number of blows in 1...2 minutes.

If the average failure in three consecutive pledges does not exceed the calculated one, then the pile driving process is considered completed.

Piles that do not give a control failure are subjected to control finishing after a break (lasting 3...4 days). If the depth of immersion of the pile has not reached 85% of the design one, and during three consecutive pledges a design failure has been received, then it is necessary to find out the reasons for this phenomenon and agree with the design organization on the procedure for further carrying out pile work.

Vibration method.

The method is based on a significant reduction in vibration of the coefficient of internal friction in the soil and friction forces on the side surface of piles. Due to this, when vibrating, driving piles requires sometimes tens of times less effort than when driving. In this case, partial compaction of the soil (vibration compaction) is also observed. The compaction zone is 1.5...3 times the diameter of the pile (depending on the type of soil and its density).

With the vibration method, the pile is driven using special mechanisms - vibratory drivers. A vibratory driver, which is an electromechanical vibrating machine, is suspended from the mast of a pile-driving installation and connected to the pile with a cap.

The action of the vibrator is based on the principle in which the horizontal centrifugal forces caused by the unbalances of the vibrator are mutually eliminated, while the vertical ones are summed up.

The vibration amplitude and mass of the vibration system (vibration driver, head and pile) must ensure destruction of the soil structure with irreversible deformations.

When choosing low-frequency loaders (420 kol/min), used when driving heavy reinforced concrete piles and shells (tubular piles with a diameter of 1000 mm or more), it is necessary that the moment of the eccentrics exceeds the weight of the vibration system by at least 7 times for light soils and 11 times for medium to heavy pounds.

During vibration immersion in clay or heavy loam, a crushed clay pad is formed under the lower end of the pile, which causes a significant (up to 40%) reduction in the load-bearing capacity of the pile. To eliminate the occurrence of this phenomenon, the pile is immersed in the final segment of 15...20 cm in length using the impact method.

To immerse lightweight (weighing up to 3 tons) piles and metal sheet piles into soils that do not provide much drag under the tip of the pile, high-frequency (1500 vibrations per minute or more) vibratory drivers with a sprung load are used, which consist of a vibrator and a using an additional weight spring system and a drive electric motor.

The vibration method is most effective for loose, water-saturated pounds. The use of the vibration method for fusing piles into low-moisture dense pounds is possible only when constructing leading wells, i.e., when previously performing another process that requires drilling mechanisms.

More universal is the vibroimpact method of driving piles using vibratory hammers.

The most common spring vibratory hammers work as follows. When the shafts with unbalances rotate in opposite directions, the vibration exciter performs periodic oscillations. When the gap between the vibration exciter hammer and the pile is less than the vibration amplitude of the vibration exciter, the hammer periodically strikes the anvil of the pile cap.

Vibratory hammers can self-adjust, i.e., increase impact energy with increasing resistance per pound to pile pushing.

The mass of the impact part (vibration exciter) of the vibrating hammer in relation to the forcing of reinforced concrete piles must be at least 50% of the mass of the pile and be 650...1350 kg.

In construction practice, a method is also used that is based on the combined effects of vibration (or vibration with impact) and static load. The vibration-pressing installation consists of two frames. On the rear frame there is an electric generator powered by a tractor engine and a double-drum winch, on the front frame there is a guide boom with a vibrating driver and blocks through which the pressing rope from the winch passes to the vibrating driver. When the vibratory-pressing installation takes its working position (the suspension hook of the vibratory driver must be above the place where the pile is immersed), the vibratory driver is lowered down, the head is connected to the pile and raised to the upper position, and the pile is installed at the place where it was driven. After turning on the vibratory driver and winch, the pile is immersed due to its own weight, the weight of the vibrating driver and part of the weight of the tractor transmitted by the pressing rope through the vibratory driver to the pile. At the same time, the pile is subject to vibration created by a low-frequency loader with a sprung plate.

The vibration pressing method does not require the construction of any paths for working movements, eliminates the destruction of piles and is especially effective when driving piles up to 6 m in length.

Driving piles by screwing

The method is based on screwing steel and reinforced concrete piles with steel tips using installations mounted on cars or car tractors.

The method is used mainly when constructing foundations for masts of power lines, radio communications and other structures, where the load-bearing capacity of screw piles and their resistance to pulling out can be sufficiently used. These installations have a working body, four hydraulic outriggers, a drive for rotating and tilting the working body, a hydraulic system, a control panel and auxiliary equipment.

The design of the working body allows you to perform the following operations: pull the screw pile inside the pipe of the working body (previously put an inventory metal shell on the pile), provide a given angle of immersion of the pile within 0...450 from the vertical, immerse the pile into the ground by rotation with the simultaneous use of axial force , if necessary, remove the pile from the ground. The rotation of the working element and its tilt are carried out from the vehicle's power take-off through the corresponding gearboxes.

The working operations when driving a pile using the screwing method are similar to the operations performed when driving piles using the driving method or vibratory driving. Only instead of installing and removing the head cap, they put on and remove the shells.

Methods to speed up the process of driving piles

Such methods are based either on the pressure energy of a water jet (soil erosion) or on the use of the effect of electroosmosis.

By washing, the soil is loosened and partially washed away with jets of water flowing under pressure from several tubes with a diameter of 38... 62 mm mounted on a pile. In this case, the resistance of the pound at the tip of the pile is reduced, and the shaft rising along the shaft erodes the soil, thereby reducing friction on the side surfaces of the pile. The location of the flushing tubes can be lateral, when two or four flushing tubes with tips are located on the sides of the pile, and central, when one single or multi-jet tip is placed in the center of the pile being immersed. With lateral erosion (compared to central erosion), more favorable conditions are created to reduce friction forces on the side surface of the piles. When positioned sideways, the flushing tubes are attached in such a way that the tips are located at the piles 30...40 cm above the tip.

To wash away the soil, water is supplied into the tubes under a pressure of at least 0.5 MPa. When undermining, the adhesion between soil particles under the base and partially along the side surface of the piles is disrupted, which can lead to a decrease in the load-bearing capacity of the pile. Therefore, the piles are driven in the last meter or two meters without undermining.

The use of erosion is not allowed if there is a threat of subsidence of nearby structures, as well as in the presence of subsidence soils.

Driving piles using electroosmosis is used in the presence of water-saturated dense clay soils, moraine loams and clays. To practically implement the method, the immersed pile is connected to the positive pole (anode) of the current source, and the immersed pile adjacent to it is connected to the negative pole (cathode) of the same current source. When the current is turned on around the pile (anode), the humidity of the pound decreases, and near the pile being driven (cathode), on the contrary, it increases. After the current supply is stopped, the initial state of the pound water is restored and the bearing capacity of the piles, which are cathodes, increases.

Additional operations when fusing reinforced concrete piles using electroosmosis involve equipping the piles with steel strips - electrodes, the area of which occupies 20...25% of the lateral surface of the piles. This operation is eliminated when metal piles are tightened using the screwing method.

The use of the electroosmosis method makes it possible to speed up the process of pouring the pile by 25...40%, as well as reduce the loads required for pouring the pile.

Driving piles into frozen soils

When driving piles in winter during seasonally freezing conditions, it is necessary to perform additional operations or separate processes that increase the complexity and duration of piling work. It is possible to manage without additional operations, but with a slight decrease in the productivity of installations, when pushing piles with powerful hammers and vibratory hammers, if the freezing depth does not exceed 0.7 m. In other cases, conditions close to summer should be created. To do this, it is necessary to prevent freezing of the pound by insulating the places where piles are driven in advance with available materials (sawdust, straw, etc.). For the same purposes, frozen soil is destroyed at the site of driving piles using mechanical methods, leading holes are made using drilling machines and vibrating impact installations, or slots are cut along the rows of future piles using bar machines, and the layer of frozen pound is thawed (all these processes are performed using methods adopted in the development of frozen pound ). The process of deflating the piles itself is identical to the processes adopted for summer conditions.

Methods for driving piles into permafrost soils are characterized by technological features determined by the physical and mechanical properties of frozen soils, which in an undisturbed state have a high bearing capacity. Therefore, in these conditions, when performing pile work, it is necessary to preserve frozen soils in their natural state as much as possible, and in areas where the soil structure is disturbed during the process of driving piles, the properties of these soils should be restored. Freezing of piles, or, in other words, freezing of the surface of the pile with the soil, leads to the fact that they acquire a high load-bearing capacity. This phenomenon can be effectively used when driving piles into hard frozen soils, conventionally classified as low-temperature. These pounds have an average annual temperature at a depth of 5... 10 m no higher than - 0.6 ° C for sandy loams - 1 ° C for loams and - 5 ° C for clays.

Piles are pressed into hard-frozen pounds mainly by two methods: into thawed pounds or into drilled holes whose diameter exceeds the largest cross-sectional dimension of the pile. When pouring piles into thawed soil, first thaw it and then push the piles into the liquefied cavity formed in the frozen pound. The soil is thawed using a steam needle perforated at the lower end. Under the action of steam (pressure 0.4...0.8 MPa) coming out at the tip of the needle, the pound is liquefied to a fluid state and the pile is driven into it to the design depth.

In pounds with a small amount of ice, you can obtain a cavity of the required size in a short time (1... 3 hours), and in pounds with a high degree of ice saturation, this process occurs within 6...8 hours. The rate of needle insertion is determined using this calculation so that the diameter of the thawed cavity is 2... 3 times greater than the largest size of the pile in cross section. Some time after the pile has been sunk, freezing occurs and, being embedded, as it were, in the thickness of the permafrost soil, it acquires the necessary load-bearing capacity.

The method of driving a pile into drilled wells involves the following sequence of processes and operations: drilling a well, filling the well with sand-clay solution to the point at which the volume of solution with some excess is sufficient to fill the gaps between the walls of the pile well after its immersion, immersion of the pile, accompanied by squeezing out the solution , removing the casing.

In plastic-frozen high-temperature (with an average annual temperature not lower than - GS) piles are driven by driving or drilling method. Methods of pouring into a thawed pound and into wells with a larger cross-section than the cross-section of the piles in conditions of high-temperature pound are of little use due to the fact that freezing of the pile occurs very slowly. Piles can be driven into plastically frozen silty loams and sandy loams that do not contain inclusions, and only during the period of seasonal thawing, since in winter the active layer cools to -5... -10°C and becomes hard frozen. Therefore, the scope of application of the drilling method is much wider.

The piles are drilled using the drilling method in two stages. At the first stage, a leading well is drilled, the diameter of which is taken to be 1...2 cm less than the side of the pile. At the second stage, the pile is driven using a vibratory hammer or diesel hammer. In this case, the pound is pressed from the corners of the pile towards the middle of its walls. The soil thaws due to thermal energy transformed from mechanical energy developed by the hammer and partial squeezing of the pound from the well. It is enough to thaw a thin layer of the pound and the temperature in the area adjacent to the pile will increase by an insignificant amount, and the process of freezing of the pile into the pound will occur in a short time. The use of leading wells makes it possible to increase the accuracy of pile installation, ensure its expansion to the designed depth, eliminate cases of pile breakage when hit by sharp boulders, etc.

Pile driving sequence

The order of driving piles depends on the location of the piles in the pile field and the parameters of the pile-loading equipment. In addition, subsequent processes for constructing the pile grillage should be taken into account.

The most common is the row system for driving piles, used when they are arranged in a straight line in separate rows or bushes.

The spiral system provides for driving piles in concentric rows from the edges to the center of the pile field; in some cases it makes it possible to obtain the minimum length of the path of the pile-loading installation. If the distance between the centers of the piles is less than five of their diameters (or, accordingly, the dimensions of the cross-sectional sides), then the soil in the middle of the pile field may become compacted, which complicates the process. However, there are cases when it is impossible to load piles located in this zone. In this case, the piles must be driven from the center to the edges of the pile field.

For large distances between piles, the driving order is determined by technological considerations, primarily the use of efficient equipment. Thus, in some tower-type piledrivers, the masts rest on retractable frames located above trolley platforms and shifting by about 1 m. These piledrivers can be used to drive piles of two rows from one piledriver site. For the construction of the underground part of residential buildings, special cranes are used, equipped with mounted pile driver equipment, a double-drum winch for lifting the hammer and pile, and a diesel hammer. Such cranes can drive piles 8 m long, moving along a rail track laid approximately at the zero level along the edge of the foundation pit of a building under construction.

When constructing pile foundations for long-term residential and industrial buildings, it is very effective to drive piles using a bridge piling machine. This installation is a movable bridge along which a trolley with a pile driver moves. Piles 8...12 m long are driven with a diesel hammer. Since the pile driver's mast is lowered below the floor of the pile driver's working platform, it is possible to drive piles below the bridge frame. This installation is a kind of coordinate device that facilitates the breakdown of pile immersion sites, while it is possible to install piles with a high degree of accuracy. The location of the pile within the coverage area of the bridge installation allows the duration of operations to pull the pile to be reduced, which, in turn, increases the productivity of the entire process.

The installation of sheet piling fencing made of metal and wooden sheet piles begins with the raising of lighthouse piles, to which 2...3 tiers of screeds are attached, serving as guides when driving the sheet piles.

When deepening piles in winter using electric rod heaters to thaw the frozen pound, the pile driving area is divided into five capture sections: in the first, wells are drilled, in the second, the wells are already pre-drilled and insulated from above, in the third, the piles are deepened. The interval between the excavation of the well and the insertion of the pile into it should not exceed one shift. In approximately the same way, with a breakdown into grips, the order of raising piles is established, if the installation of grillages begins before the completion of pushing all the piles for a building or structure.

Selection of methods for driving piles and pile-driving equipment

When driving piles, the main factors determining the choice of method are the physical and mechanical properties of the soil, the volume of pile work, the type of piles, the depth of driving, the performance of the pile-driving installations and pile drivers used.

The volume of work is most often measured by the number of piles or meters of the total length of the immersed part of the piles, and the sheet piling row - by meters of the length of the sheet piling row of a particular immersion depth. Accordingly, equipment productivity is measured per hour or more per shift.

Average data on the time standards for driving piles using various installations for different types of hammers and loaders, as well as the composition of the working units, are given in ENiR. However, the diversity and complexity of the operating factors in most cases require the establishment of general dependencies for a certain speed and duration of immersion of piles into the ground for specific conditions. To do this, carry out a test driving of piles within the area of the pile field using the same equipment that is supposed to be used. Based on the test driving data of at least five piles in different places of the site, the average duration of driving and the estimated productivity of pile-loading equipment for the specific conditions of each object are established.

The type of pile-loading installation chosen largely depends on the volume of piling work. This is explained by the fact that for tower-type pile drivers, bridge piling machines and some other installations, rail tracks are required, which are advisable to lay only when there are a large number of piles being driven. In addition, installing a piledriver is more labor-intensive than preparing a mobile installation.

The number of machines required to perform piling work is determined based on the operational shift productivity of the pile-loading installation:

Psm = 480 kv / (t0 + tv),

where kв is the utilization factor of the installation over time (0.9 can be taken), 480 is the duration of the shift, min, t0 is the execution of the main operation of driving piles, min, tв is the duration of auxiliary operations, including moving the installation, min.

Knowing Psm and the established period for the production of pile work, we obtain the required number of pile-loading installations:

Construction of overhead lines