The company "Installation of Pile" offers services for driving driven reinforced concrete piles with highly productive diesel hammers. Our equipment is represented by tubular and rod hammers with a hammer weight from 1.5 to 3 tons. These units effectively drive piles into all types of soil common in the central region of Russia.

This page provides information about the technology of driving piles with diesel hammers. We will review the specification and specifications of this equipment, types of hammers and their functionality.

Diesel hammers are attachments

The scope of use of diesel hammers is extensive; this equipment is used for the following purposes:

• For driving reinforced concrete piles (square, rectangular, round, composite structures);
• For driving metal sheet piles (Z-shaped, trough-shaped, flat).

Important: hammers are installed on piling machines with wheeled or tracked layout. The pile driver mast and diesel hammer have a unified fastening system, which allows the pile driver to be equipped with any model of impact pile driving unit.

Rice. 1.1

The cross-section and configuration of piles and sheet piles that a diesel hammer can work with depend on the shape of its head - the fastening element by which the hammer is fixed to the shaft of the submerged structure. Each specific section (30*30, 40*40 cm, etc.) requires the use of an appropriate headrest.

In the factory configuration, the diesel hammer has a set of caps for the most common standard sizes of piles; if necessary, additional caps are purchased separately.

Types of diesel hammers for driving piles

• Lightweight - striker weight up to 700 kg;
• Medium-heavy - up to 2000 kg;
• Heavy - from 2500 kg.

Important: A division is also made according to the shape of the structure, according to which tubular-type units and rod hammers are classified.

• Rod hammers

Rice. 1.2: Rod hammer diagram

The basic functional units of this equipment include:

• Piston block fixed on a steel hinge plate;
• Parallel pipes serving as guide elements of the striker;
• Diesel fuel injection system into the piston;
• The cat is a knot that secures the head of the hammer.

Rice. 1.3

The piston block, which is a cast structure formed in the inner part of the cylinder, in turn consists of a piston and compression rings. The fuel injection system is represented by a nozzle connected to the fuel pump through a supply hose.

On a hinged plate fixed on top of the chabot there are 2 guide frames parallel to each other, connected by a steel bridge on the upper contour. During operation, the firing pin moves along the frame, in the body of which the fuel detonation chamber is located.

• Tubular hammers

Rice. 1.4

The differences between tubular mechanisms are that the guiding function in this equipment is performed by a body, which is a steel cylindrical pipe. The impact part of the tubular hammer is also its piston, into which the fuel mixture is supplied by a nozzle.

Rice. 1.5

Important: the closed body of tubular hammers allows for forced cooling, which is absent in rod units. Its presence is one of the key advantages of tubular structures over rod ones - they are subject to long-term operation without interruptions for natural cooling, whereas when using diesel rod hammers it is necessary to withstand forced pauses to prevent overheating of the equipment.

Technical characteristics of diesel hammers

The most popular series of diesel hammers in domestic construction are the SP and UR hammers; you can see their technical characteristics in the image below:

Rice. 1.6: Specification of hammers of the SP series

The weight of the impact part in diesel rod hammers can reach up to 3 tons, while their maximum impact energy does not exceed 42 kJ, the range of the number of impacts on a pile per minute is 45-55 pcs.

Rice. 1.7

Due to limited power, such structures are used for installing reinforced concrete piles and sheet piles in low and medium-density soil - tubular hammers are used to carry out foundation work in hard soils.

These units can operate in a temperature range from -35 to +40 degrees (in operating conditions in frosts of more than 20 degrees, the piston assembly of the hammer must be preheated). For tubular units, the mass of the striker is more variable - its weight can be 5, 3.5, 2.5, 1.8 or 1.25 tons. The range of impact power is from 35 to 170 kJ. Operating speed - up to 45 beats/min.

Technology for driving piles with diesel hammers

• Initially, the pile driver is placed at the immersion site, then it winches the pile from the temporary warehouse, the shaft is slung with cables, the driving position is set and brought under the head of the hammer;
• The pillar is fixed to the pile driver mast, the hammer is lowered onto it and the pile is mated to the cap;
• The impact striker of the unit is lifted into the upper part of the housing by means of a headframe winch along guides;
• After the driver turns on the hammer release lever, under the influence of its own weight, it falls along the guides to the hammer attached to the head;
• When the striker falls, it activates fuel pump and the nozzle supplies diesel fuel to the combustion chamber;
• When the striker and the cylinder come into contact, the piston strikes the cylindrical recess of the combustion chamber, causing the mixture in it to spontaneously ignite and detonate;
• Thanks to the energy generated as a result of the fuel explosion, the firing pin is thrown up along the guides;
• When the lifting energy of the striker is balanced by the force of gravity, the striker begins to fall back down under its own weight.

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 into 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 filling on the pile head is created using special mechanisms - hammers of the most different types, the main ones being diesel.

On construction sites rod and tubular diesel hammers are used.

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.

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 hammer of the vibration exciter and the pile is less than the amplitude of vibration 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.

Immersion of 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 piling work, it is necessary to preserve frozen soils in their natural state, 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.

Pounds with a little ice can get a cavity required sizes 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 retraction is determined so that the diameter of the thawed cavity is 2... 3 times the largest cross-sectional size of the pile. 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 widespread 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 the trolley platforms and shift 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 locations, and 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 construction of sheet piling fencing made of metal and wooden sheet piles begins with the installation of lighthouse piles, to which 2...3 tiers of screeds are attached, serving as guides when driving the sheet piles.

When pouring 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 on top, 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 piling work, the type of piles, the depth of immersion, 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. According to the test immersion of at least five piles in various places site is installed average duration immersion and the calculated productivity of pile-loading equipment for the specific conditions of each object.

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

Pile hammers are used mechanical (suspended), steam-air and diesel.

Mechanical hammers, with which piles are driven using the energy of their free fall, have low productivity. They are rarely used for driving small piles.

Steam-air hammers widely used for driving reinforced concrete and steel piles, including driving heavy piles into dense cohesive soils. These hammers operate using steam or compressed air; According to their design and principle of operation, they are divided into single and double action hammers.

Single action hammers There are manual, semi-automatic and automatic controls.

Manual Hammers simple and reliable in operation, but have low frequency blows (up to 25 per minute). The weight of the impact part in single-action hammers reaches 8000 kg.

Double action hammers are more productive and work automatically, but have a lighter impact part, which limits their use for driving heavy piles. There are double-action steam-air hammers adapted for working underwater.

In winter conditions, it is better not to use steam-air hammers. compressed air, but steam, since with the pneumatic method water condenses and freezes in the mechanisms.

Diesel hammers They are widely used mainly for driving relatively small piles and are divided into rod, tubular and air-buffered. In rod hammers the impact part is a cylinder, and in tubular hammers it is a piston. The weight of the impact part is from 400 to 2500 kg.

The disadvantages of diesel hammers include:

Low efficiency - up to 60% of kinetic energy is spent on compressing the air in the cylinder;

Inadequacy of work in the initial period and in weak soils - with little resistance to immersion, sufficient compression of the combustible mixture does not occur and therefore the hammer stops working;

Operation is ineffective at low air temperatures.

The general organization of piling work at a bridge construction site depends on the choice of mechanisms for driving piles. The choice of pile driving units, including pile hammers, depends on the properties of the soil, as well as the weight of the pile, its design, the required immersion depth and load-bearing capacity.

The weight of the impact part of a single-action hammer (including a diesel hammer) must be greater than the weight of the pile when its length is more than 12 m. For a pile length of less than 12 m, the weight of the impact part of the hammer must exceed the weight of the pile by more than 1.25 times - when immersed in soil medium density.

In different soil conditions, the effect of driving piles can depend both on the energy of the hammer impact and on the frequency of its impacts. Only with an optimal ratio of all parameters of the pile-driving unit, corresponding to specific soil conditions, can piles be successfully driven into the ground.

Driving piles with hammers into sandy soils that are completely saturated with water in some cases turns out to be difficult. Increasing the weight of the impact part of the hammer has no effect. Water is displaced more intensely and, therefore, the speed of immersion of the pile increases, also undermining the soil, which causes a flow of water along the walls of the piles, friction decreases and a path opens for free water to exit from the pores of the soil. For water-saturated sandy soils, it is preferable to vibrate piles and drive them with hammers high frequency blows and using washing.

When piles are immersed in clayey soils, they become compacted, structural bonds are broken, and as a result, part of the cohesive water passes into free water, i.e. the soil liquefies (thixotropin phenomenon). This phenomenon facilitates the immersion of piles, and it occurs more intensely at a relatively higher frequency of hammer blows. In addition, the possibility of successfully driving piles into clay soils depends on many

other reasons and mainly from the consistency and moisture of the soil. High adhesion forces of clay soils to the pile sharply reduce the sinking effect; in water-saturated clay soils, immersion is difficult even with low density; In dense clay soils, the resistance to immersion increases. Washing piles in clayey soils rarely gives positive results. In dense clayey

It is better to drive pile soils using pile hammers with heavy weight impact part - single-action steam-air hammers. To make it easier to drive tubular piles into clay, they are sometimes driven with an open end and the soil removed from their cavity.

In sandy loam or weak loams Piles can be successfully driven using pile hammers using, if necessary, undermining.

Piles must be driven into the ground until the amount of subsidence from one impact reaches a design value called failure (the arithmetic average of the settlement from several impacts).

Design failure indirectly characterizes the bearing capacity of the pile on the ground, i.e. is the dynamic equivalent of the maximum static load on the pile. The initial failure obtained after completion of pile driving is usually not true, since after a period of interruption the magnitude of the failure changes. In low-moisture sandy soils, failure increases (resistance decreases), and in clayey soils it decreases.

The productivity of piling work depends on both the right choice piling unit, and from auxiliary driving operations, which take up to 80% of the time. For pile work, pile drivers or cranes are used. Jib and gantry cranes are equipped with guide booms and other auxiliary equipment. To guide piles during driving, especially to guide inclined piles, guide devices are also used in the form of frames made from inventory elements of UICM or portable devices installed on spacer mounts of pits.

The pile drivers and cranes used for driving piles must be maneuverable and allow them to be quickly moved, as well as carry out all auxiliary work. Drivers should be light, fairly rigid, easy to assemble and, if possible, universal. The dimensions of the pile driver and its design are selected depending on the size of the piles, the conditions for their immersion, as well as the pile-driving unit used. If pile drivers are intended for driving relatively short and light piles or sheet piling, then they can be manufactured in construction. Wooden collapsible headframes can be made up to 15 m high; Wooden pile drivers with two booms are used, making it possible to drive two piles at a time. Metal stock pile drivers are most often used. Among them are pile drivers for diesel hammers, made of various rolled profiles and pipes and equipped with wheels for movement on rails. To drive heavy long piles, including inclined ones, universal pile drivers are used that are moved on rails. These pile drivers can be tilted up to 5:1 using long screws installed between the tower and the platform. Most universal headframes are fully rotatable in the horizontal plane, and the platform usually houses a steam boiler, winch and turning mechanisms. When rearranging the trolley and installing it on rails in a different direction, the frame of the pile driver is lifted with jacks secured under the platform. In areas covered with water, it is advisable to drive piles using floating pile drivers, which are placed on dinghies made of metal pontoons (usually on KS inventory pontoons) and secured with anchors.

Along with pile drivers, various cranes are widely used in bridge construction for driving piles: jib stationary derrick cranes, jib cranes on crawler or truck-mounted tracks, and portal cranes. In areas covered with water, floating cranes are suitable for this purpose.

The use of a crane for driving piles is especially advisable if it is used for all support construction work, i.e. for driving sheet piles, extracting soil and concreting the support body, and, in addition, for installing spans. Thus, universal cranes with replaceable equipment allow you to drive sheet piling and piles, develop and remove soil from pits or sinkholes, supply concrete mixture, lift sliding formwork or supply formwork panels for assembly, assemble supports from blocks, install prefabricated metal and reinforced concrete spans etc.

The cranes used for driving piles are equipped with guide booms. Short guides suspended from a crane are used, which are periodically lowered as the pile is driven in such a way that the hammer does not go beyond their limits during operation. More often, long guides are used, suspended from the crane boom, in the lower part rigidly attached to the crane body using a connection that allows you to change the inclination of the guide and the reach of the crane boom.

In cases where the design elevations of the pile heads are below the water level, pile hammers capable of working under water are used, or so-called “headstocks” are used, installed between the end of the pile and the hammer. Headstocks are sections of piles or corresponding inventory structures.

The sequence of driving piles depends on the shape of the foundation and soil properties. number of piles and equipment used. With a small number of rows, piles are driven sequentially in rows, starting from the outer one. In multi-row foundations, a spiral sequence is used, starting from the central piles in order to avoid over-compaction of the soil, which prevents the immersion of subsequent piles.

So, piles are a structural element that transfers loads from a building (structure) to soils located significantly below the conditional zero level. Reinforced concrete piles of square section 300x300mm, 350x350mm, 400x400mm with a length from 3m to 16m and composite piles up to 32m long are optimal choice for construction on soft soils. In bridge construction, centrifuged (hollow) piles with a diameter of 600 mm are used.

The technology has remained virtually unchanged for many years, but in recent years certain restrictions have been introduced on the use of pile hammers in urban areas. In densely built-up urban areas, bored piles are used, which are much more expensive, but their installation does not pose the risk of destroying neighboring dilapidated buildings. Or they perform a set of works (installation of sheet piling, preliminary soil selection, leader drilling) to reduce the negative load on existing building foundations and utility networks.

Methods for driving piles into the ground.

Before the piles begin to be immersed in the ground, a complex is performed preparatory work in accordance with the piling work project, which includes:

• delivery and storage of finished reinforced concrete piles,
• delivery and installation of equipment for driving, development of a movement diagram for a pile-driving installation indicating the order of driving piles in accordance with the PPR;
• planning the foundation site (in the spring-autumn period, as a rule, backfill is made from broken bricks or crushed stone);
• geodetic breakdown of the axes of pile rows;
• test driving of piles to clarify the calculation of the load-bearing capacity of the pile (carrying out static and dynamic tests).

The sequence of driving piles is established by the project, taking into account the properties of the soil and the maneuvering characteristics of the equipment.

Geodetic layout, i.e. The location of the piles is carried out by our specialists based on the drawings and the building axes received from the customer. In accordance with regulatory requirements, permissible deviations piles from the design axis are 0.2d for linear driving, or 0.3d if the piles will be combined with a foundation slab. d - pile section, i.e. when driving 300x300mm piles under the “slab”, valid value the deviation will be 9 centimeters.

Various methods are used to drive piles

• impact method - driving piles with a hammer
• pressing method
• vibration method - driving piles using vibration
• drilling and installation of piles into a well (using leader drilling)

Impact method.

Driving is carried out with hammers of various types with a striking part weighing, usually 1.8 - 12 tons, mounted on heavy, usually tracked equipment (headframes, crawler cranes, cable and hydraulic excavators). Piles are driven into the ground by applying a vertical (sometimes inclined) load.

The base machine is used to hook the pile, lift it and drive it into the hammer head, which moves along the mast guide. Then the hammer drives the pile into the ground by releasing the impact part.

Driving the pile begins with several light blows, followed by 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 corrected by supporting, tightening, etc., or pulled out and driven in again. Pile driving continues until the failure specified by the design is achieved - the amount of immersion of the pile from one hammer blow after the completion of driving. Driving piles when approaching the design value of immersion is carried out with “collaterals”, i.e. 10 hammer blows in a row. The immersion of the pile from one foundation is measured with an accuracy of 1 mm. Pile failure is determined as the quotient of the value of pile immersion from one foundation divided by the number of blows in the foundation.

Indentation method.

The pile driving method is used in the reconstruction of buildings that cannot be demolished because they are of historical value and are protected by law.

The most effective area of ​​​​application of pile pressing technology is the driving of reinforced concrete piles and sheet pilings near or inside existing buildings and structures in densely built-up conditions, near dilapidated and emergency structures, in landslide zones and in other places where it is impossible to drive piles using the impact method or vibration driving due to inadmissibility of dynamic, vibration and noise impacts. Equipment for pressing piles is quite cumbersome, performance leaves much to be desired, but sometimes this non-impact method is simply irreplaceable. Sunward walking pile driving units are most widely used.

Vibration method - driving piles (sheet piles) using vibration.

The vibration driving method is effective when driving piles into water-saturated sandy and poorly cohesive soils. In this case, the sandy soil liquefies and the friction forces on the side surface sharply decrease. After the vibration stops, these friction forces are restored.

Vibratory driver - exciter of vibrations along the axis of the pile. A device with a rotator and a load with a displaced center of gravity driven by an electric motor or hydraulic station is suspended on the head of the pile. Due to the significant weight of the vibratory driver and vibrations, the pile (tongue) is immersed in the ground. Vibration dampers, unlike hammers, have certain restrictions on the types of soil in which they can work. Also, when vibratory driving, leader drilling is often used.

Pile driving technology using leader drilling

Leader drilling is drilling performed before the pile is immersed. Leader drilling can have several goals: reducing the dynamic load transmitted when driving a pile to nearby buildings, reducing noise from the operation of a diesel hammer, increasing the length of the pile used (when driven into dense soils). Also, leader drilling is used if there is a sand layer of more than 2 meters in the geological section. The decision to construct leader wells is made by the designer based on a geotechnical survey report.

The diameter of the auger for leader drilling under 300x300 piles is taken to be 200mm-250mm depending on the category of soil. The drilling depth is usually 0.5 meters less than the pile immersion depth. Also, for example, to drive a 10-meter pile, when a meter-long sand layer occurs at a depth of 5 meters, leader drilling can be assigned to a depth of 6-6.5 meters to reduce the negative effect of sand when driving piles.

During leader drilling, the soil selected by augers from the well increases the elevation of the earth's surface (pit) by 10 or more centimeters (depending on the depth and diameter of the drilling. It is necessary to competently approach the drilling work because when driving piles, the well, located in the immediate vicinity often crumbles due to dynamic loads during hammer operation.For the construction of leader wells during piling work, our company uses PBU-2-317, LBU-50, URB-2A2 installations.

Machines and equipment for driving piles

Diesel hammers based on full-rotary excavators of the EO series are used. Excavators are crawler-mounted and serve, by and large, to move piling equipment. The piling equipment is the mast and the hammer itself. The hammer moves along guides on the mast.

But the most effective pile drivers with a hydraulic hammer are: Junttan PM20, Junttan PM22, Junttan PM25, Hitachi KH-150-3, Hitachi KH-180-2, Nippon-Sharyo DH, Banut, PVE, Liebherr.

If necessary, the hammer can be replaced with drilling equipment for leader drilling. When relocating from object to object, the hammer and mast (consisting of 2-3 parts) are removed from the base machine. Considering the oversized dimensions and weight of the pile driver, its relocation is carried out with a special permit from the traffic police with escort.

Driving hammers.

The hammer consists of a striking part that moves along the guides, a chabot (fixed part) and a head. Based on the type of action, a distinction is made between diesel hammers and hydraulic hammers.

The photo shows very common diesel rod hammers and domestic Ropot hydraulic hammers. Between the shock and stationary cylinders there is a regular diesel engine cylinder. The operating principle is also very similar to ordinary diesel engine. The impact part is lifted by a cable, at this moment the fuel supply is opened, then the hammer is dropped and an explosion occurs in the cylinder because as is known, inflammation diesel fuel comes from compression. Due to the energy of the hammer impact and the explosion in the cylinder, the pile sinks, and the impact part of the hammer is thrown up and falls again. This happens until the fuel supply stops.

The hydraulic hammer differs in its drive mechanism. Instead of an internal combustion engine cylinder, the impact part is driven by hydraulics. Moreover, with the help of hydraulics, the striking part not only rises, but also lowers, i.e. does not reset. Due to this, it is possible to adjust the lifting height. If the diesel hammer hits with almost the same frequency, the hydraulic hammer can hit both with maximum force and with small frequent blows, which is very convenient when working on sandy soils. The weight of the impact part of hydraulic hammers is 3-12, in contrast to diesel hammers, whose impact part weighs 1.8-3 tons. Although there are imported diesel hammers with impact parts of 10, 14, 16 tons.

Environmental and external advantages when working with a hydraulic hammer:

• Reliability, reliability, ease of operation, all-season, all-weather.
• Impact energy regulation.
• Minimal seismic impact on the ground, allowing piling work in dense urban areas without danger to nearby buildings.
• Productivity is 2 times higher than similar free fall pile driving devices.
• Reduced noise.
• No exhaust gases, environmentally friendly.
• Reduced vibration.

When driving reinforced concrete and steel piles, caps must be used to protect the pile head from damage when it is hit with a hammer from a pile driving machine. When driving wooden piles, the head of the pile is protected from being weakened by a yoke, which is a cylindrical ring made of strip steel, placed on the head of the pile. The lower end of the wooden pile is sharpened in the form of a tetrahedral or triangular pyramid. If there are solid inclusions in the soil, a metal shoe is placed on the tip of the pile to protect the tip from getting wet. Wooden piles are used provided the head of the pile is laid below the groundwater level.

To prevent powerful blows from breaking the head of the pile, a wooden spacer is inserted into the head of the hammer to act as a shock absorber.

SAFETY WHEN PRODUCING PILE WORKS

Installation of piling equipment and piles must be carried out without interruption until they are completely secured in place.

During the process of driving piles, it is necessary to constantly monitor the condition of the pile-driving installation; if it malfunctions, work must be stopped immediately.

The piles are dragged to the pile driver only through a pull-out block fixed at the base of the pile driver and in a straight line within sight of the winch operator.

Persons who know the rules for handling equipment and mechanisms and have passed a special technical minimum are allowed to carry out pile driving work. At. During a short stop, the hammer must be attached to the pile driver and the lifting rope must be loosened. During long stops, the hammer is lowered to the lower position and secured.

Each pile driver is equipped with an audible alarm. Before the pile hammer is put into operation, a sound signal is given.

Moving the piling rig from parking lot to parking lot is carried out only at the command of the foreman and under his supervision.

IN winter time work sites must be cleared of snow and ice and sprinkled with sand.

Quality control during driving (driving) of piles

Quality control of work on the installation of a pile foundation is carried out step by step with the execution of reports on the preparation of the pit, access roads, geodetic layout, driving of piles, and installation of a grillage.

Data on pile driving must be recorded in the “Pile Driving Log”. The main requirement for the quality of pile driving is its achievement of the specified load-bearing capacity. The permissible load on the pile depends on the depth, accuracy and technology of its immersion, as well as on soil conditions. The most reliable value of the load-bearing capacity of piles is given (experimental pile driving, trial pile driving) by their static test, but it is labor-intensive and time-consuming. Therefore, in the process of work, a less accurate, but simple and easy-to-use dynamic method of testing piles is used, the essence of which is based on the correlation of the relationship between the resistance of the pile and failure.

Pile failure is the depth of immersion of a pile into the ground from one hammer blow, defined as the arithmetic mean value of the depth of immersion of a pile from a certain number of blows (collateral). The number of blows in the deposit for suspended and single-action hammers is taken equal to 10 (for double-action hammers and vibratory hammers the number of blows or the operation of the mechanism is taken for 2 minutes). This actual failure is compared with the calculated (design) failure, which is established by designers based on engineering-geological conditions in order to control the load-bearing capacity of the pile. Failure is measured at the end of the pile driving with an accuracy of 1 mm from at least three consecutive piles. A pile that does not give the calculated (design) failure must be subjected to control finishing after resting and being sucked into the ground for 6 days - for clayey and heterogeneous soils, 10 days for water-saturated fine and silty sands. 20 days for soft and fluid-plastic clay soils. Piles that gave a false failure, or piles that were not driven 10 - 15% of the length, should be examined in order to eliminate the reasons that make driving difficult. When; if the failure during control finishing exceeds the calculated one, the design organization must conduct control tests of the piles with a static load and adjust the design of the pile foundation or part of it.

Pile driving can be carried out both to the design failure and to the design mark (established by the project). The latter is possible only in cases where soft soils lie under the tip of the pile and the load-bearing capacity of the pile does not exceed 200 kN.