RU2244065C1 - Method for screw pile driving in ground and screw pile driven by above method - Google Patents

Abstract

FIELD: building, particularly for building load-bearing foundations and securing different mechanisms and devices in ground, including permafrost ones, for driving metal tubular piles, preferably having diameters of 168 - 219 mm.

SUBSTANCE: method involves pressing pile in ground along with simultaneous driving thereof with the use of inner inventory key. Torque is initially applied to screw blade by inventory key and then as pile driving resistance increases pile shaft is also involved in torque transfer process, wherein exceeding of predetermined torque value to inventory key or pile shaft is not allowed. Screw pile comprises cylindrical tubular shaft with guiding cone, screw blade and seat formed in lower shaft part for inner inventory key installation. Shaft is formed of metal and has means for taking torque transferred from above key.

EFFECT: reduced material consumption due to providing two-stage torque transfer scheme, increased reliability of pile driving process and pile as a whole.

7 cl, 8 dwg

Description

The invention relates to construction and can be used for the construction of bearing foundations and fixing various mechanisms and devices on the ground, including in frozen soils, when screwing metal tubular piles (mainly, with a diameter of 168 ... 219 mm).

There is a method of immersing screw piles "behind the upper head of the pile shaft" (see book. M. Herod, "Application of screw piles in construction", M., 1968, p. 110), in which the torque of the pile blade is transmitted through the upper its end. At the same time, the pile head (head) is inserted into the collet of the machine, the pile is pressed into the ground and screwed into it using the slots on the head. With this method of immersion, the pile shaft must be designed for resistance to complex loading (from torsion, longitudinal bending from the axial force transmitted by the pile machine, as well as local bending from the action on the barrel of the guide rollers of the working body of the machine).

The disadvantage of this method is the increased consumption of metal to ensure the strength of the trunk, achieved by increasing the wall thickness of the pile or its diameter to the value necessary to ensure strength when immersed.

A known method of immersion of screw piles (see the book. Bogorad L.Ya. "Screw piles and anchors in electric grid construction", M., "Energy", 1967, S. 58-59, 78-83), selected as prototype, including the indentation of a pile with its simultaneous screwing using an internal inventory key. In this method, the inventory key is introduced into the internal cavity of the reinforced concrete trunk of the pile and installed in the seat of the screw shoe, while the other end of the key is fixed in the collet of the machine. With this immersion, the pile shaft does not experience torsional stresses, and when calculating it, only the loads that it will absorb from the structure, the foundation of which the pile will serve, are taken into account. The torque and axial force necessary for screwing the screw pile receives the inventory key from the machine and transfers it to the pile blades. In this regard, very strict requirements are also imposed on the rod of the inventory key, which is a steel pipe: on the one hand, its diameter must be minimal, since the diameter of the pile shaft depends on it, on the other hand, the rod must have sufficient twisting strength . When carrying out work in the Far North, the immersion of screw piles in frozen soils requires a large amount of torque. In this regard, to transfer the required torque to the blades, it is necessary to increase the diameter of the inventory key rod, and this will lead to an increase in the specified diameter above the value determined by the building loads. These measures lead to a greater consumption of metal, and, consequently, to an increase in the price of piles. In addition, as practice has shown, when installing an inventory key in a hollow reinforced concrete trunk of a pile, concrete chips on the inner surface of the trunk are possible. The resulting mechanical particles of chipped concrete can fall into the seat under the inventory key, preventing the installation of the latter, and, in general, the entire pile.

Piles are known to be installed by the methods described above.

For example, a screw pile is known, containing a barrel made of seamless steel pipe, a cast steel blade and a guide cone (see Prince M. Irodov, “The Use of Screw Piles in Construction,” Moscow, 1968, pp. 10-12 , fig. 5). In a known pile, the torque from the machine, when screwed, is transmitted to the blade through the upper head (head) of the pile shaft. Moreover, depending on the state of the soil (increased density, frozen soil), the torque perceived by the pile shaft should be increased in comparison with normal installation conditions. Therefore, to ensure the immersion of piles in such conditions, piles are used (to ensure strength) with an increased trunk diameter or with an increased wall thickness, which invariably leads to a large consumption of metal and is clearly a drawback.

Known screw pile, immersed using an internal inventory key (see book. Bogorad L.Ya. "Screw piles and anchors in electric grid construction", M., "Energy", 1967, p.25), adopted as a prototype, containing a tubular barrel of reinforced concrete, a metal screw shoe with a blade and a guide cone. Along the axis of the metal screw shoe, a landing hole is made for installing a profiled head of the lower end of the inventory key.

The inventory key used to immerse said pile consists of a headgear, a shaft and a profiled head. The cap serves to connect the key to the collet of the carriage of the working body of the machine. The inventory key shaft is a steel pipe. The profiled head is that part of the inventory key that enters the corresponding seat of the screw shoe of the pile and directly through which torque and axial load are transmitted to the pile shaft.

When immersing said pile, the torque necessary for screwing is transmitted to the screw blade only through an inventory key, and the pile shaft does not accept torsional stresses.

The use of this pile for the reasons stated earlier in the description of the known method of immersion of a screw pile (prototype), leads to an increase in material consumption.

The proposed inventions solve the problem of reducing the material consumption of a screw pile due to the use of a two-stream transmission circuit of torque to the blade of the pile when it is immersed and ensuring the implementation of the specified transmission circuit of torque.

The problem is solved in that in the method of immersion of a screw pile into the soil, including pressing the pile together with screwing it using an internal inventory key, according to the invention, when screwing the pile, the torque on the screw blade is initially transmitted using the inventory key, then as the screwing resistance increases the piles include the pile shaft in the work of transmitting torque, while not allowing the set torque to be exceeded both on the key and on tvole piles.

, величина которого определяется из соотношения:For the best implementation of the method, the inclusion of piles in the shaft when the set torque value on the inventory key is reached is automatically ensured by means of the interaction of the elements of the inventory key transmitting the torque and the device for sensing the torque located on the pile, the said key being installed in the prepared for screwing, pile in such a way that the torque transmitting elements of the inventory key in the initial state are located tion device for sensing the torque of the pile with an angular gap

, the value of which is determined from the ratio:

M _cr - the set value of the torque;

G is the shear modulus of the material of the core of the internal inventory key;

I _p is the polar moment of inertia of the cross section of the rod of the internal inventory key;

L is the length of the core of the internal inventory key.

To solve this problem, a metal screw pile is proposed, immersed by the claimed method, including a cylindrical tubular barrel with a guide cone, a screw blade, and a seat in the lower part of the barrel for an internal inventory key, in which according to the invention the pile shaft in its upper part is equipped with a device for perception torque from the above wrench.

At the same time, the device for sensing torque is configured to interact with transmitting torque elements of the inventory key when the specified value of torque is reached.

When implementing the proposed method, the above device for receiving torque can be made in the form of stops installed on the pile shaft with a protrusion in the internal cavity, or in the form of through rounded grooves at the ends diametrically located on the shaft, interacting with the aforementioned elements in the rounding zones.

In addition, to achieve the best result, the pile contains pointers, for example in the form of pictures or marks, for the oriented location of the inventory key in its seat.

Analysis of the distinguishing features of the claimed technical solutions showed:

- in the inventive method of immersion of a screw pile compared to the prototype, the torque transmission scheme from the machine to the pile blade is changed, namely, the torque is transmitted through an internal inventory key and through the pile shaft. With this scheme, the torque is initially perceived by the key, and then, as the load increases and the angle of twist of the key increases, the trunk is connected to the torque transmission operation, which reduces the load on the barrel and at the same time “does not overload” the inventory key, thereby allowing use piles with significantly reduced trunk wall thickness (from 20 to 10 mm with pile bore diameters of 168 ... 219 mm) without compromising the strength properties of piles. This, in general, helps to reduce material consumption, and hence the cost of a screw pile;

- automatic inclusion of the pile shaft into operation when the set torque value on the internal inventory key is reached is ensured by elastic twisting of the inventory key rod until it interacts with the torque sensing device located on the pile, allowing redistribution when tightening with increasing load on the inventory key torque from the inventory key to the trunk, thereby dividing its transmission into two components;

величина которого определяется, формулой- installation of the internal inventory key in the pile prepared for screwing so that its torque transmitting elements are in the initial state relative to the device for sensing the torque of the pile with an angular clearance,

whose value is determined by the formula

allows you to first use the strength capabilities of the rod of the inventory key for transmitting torque, and then transfer the rest of the necessary torque for screwing the pile through the shaft of the pile and through the inventory key at the same time.

будут отличаться друг от друга и должны определяться расчетным путем, но обязательно с учетом обеспечения прочности стержня ключа на скручивание при достижении угла

по известной зависимости (см., например, кн. Феодосьев В.И. "Сопротивление материалов". М., Наука 1972 г., с. 84, 86):For different design parameters of the inventory key (length, diameter of the rod, material used, etc.), the angle

will differ from each other and should be determined by calculation, but be sure to take into account the strength of the key rod to twist when the angle is reached

according to a known dependence (see, for example, Prince Feodosiev V.I. “Resistance of materials.” M., Nauka 1972, p. 84, 86):

τ _max - maximum allowable tangential stresses of the key material;

W _p is the polar moment of resistance;

- supplying the pile shaft in its upper part with a device for receiving torque from the inventory key ensures that when the pile is screwed as the inventory key is twisted to a certain angle (depending on the rigidity of the key), torque is transmitted to the screw blades through the barrel. In this case, the ratio of the geometrical dimensions of the pile and the key, as well as the mechanical characteristics of the materials, must be such as to ensure that at the rated torque of the load on the key, the maximum permissible stresses are simultaneously reached both in the inventory key and in the pile shaft. This allows you to fully use the strength properties of materials and thereby minimize their consumption, which helps to solve the problem;

- the implementation of the device for the perception of torque in the form of stops installed on the pile shaft with a protrusion into the internal cavity or in the form of through rounded grooves at the ends diametrically located on the shaft, is the most acceptable in terms of material costs and manufacturing technology;

- the implementation of pointers for the oriented location of the inventory key in the seat allows you to reduce the time to install it;

The invention is illustrated by drawings, which depict:

figure 1 - diagram of a method of immersion of a screw pile;

figure 2 is a view A (enlarged) in figure 1, which shows a screw pile with an installed internal inventory key;

figure 3 is a section bB in figure 2, which shows the implementation of the device for the perception of torque in the form of stops;

figure 4 is a section bB in figure 2, which shows the implementation of the device for the perception of torque in the form of grooves;

on Fig.5 - stress diagram in the pile shaft and inventory key when immersed by the claimed method;

figure 6 - screw pile, immersed without the use of an internal inventory key;

in Fig.7 is a section bb in Fig.6 with the image of the stress diagram in the pile shaft;

in Fig.8 is a section bB in Fig.2 with a plot of stresses in the pile shaft and inventory key, interconnected without the possibility of mutual angular movement;

Immersion (screwing) of the screw pile 1 into the soil is carried out by the working body 2 of the machine for screwing the piles (Fig.1, 2) by applying the axial force P and torque M _cr . The torque M _cr necessary for screwing is initially transferred from the working body 2 of the machine to the screw blade 3 by means of an inventory key 4, then, as the resistance increases and, consequently, the twist angle of the key 4 increases, the shaft 5 of the pile is connected to the torque transmission, forming the second stream of torque to the blade 3, acting simultaneously with the torque transmitted through the inventory key 4.

Screw pile 1, immersed by the claimed method, includes a steel tubular barrel 5 (figure 2) with a guide cone 6 and a screw blade 3. To reduce the complexity of manufacturing, the screw blade 3 is made by winding from a steel strip and is welded to the barrel 5. In the lower part of the barrel 5 in the guide cone 6, a seat 7 is made, for example in the shape of a hexagonal recess, for installing the internal inventory key 4. In the upper part, the barrel 5 is equipped with a device 8 for receiving torque from the key 4.

The internal inventory key 4, used when immersing piles, is made in the form of a metal tubular rod 9, with a cap 10 in its upper part. In the lower part of the key, a profiled head 11 is made, and the form of its execution corresponds to the shape of the seat 7 of the pile shaft, for example, in the form of a hexagon. On the key 4, elements 12 are made for transmitting torque. In the process of immersion piles, they interact with the device 8 for the perception of torque.

₁. При этом контактирующие поверхности выступов 14 расположены относительно упоров 13 сваи с угловым смещением (угол

₁ за вычетом половины угловых размеров ширины выступов 14 и упоров 13).As an example of a specific design of the piles, the device 8 is made in the form of stops 13 (Fig. 3) mounted on the pile shaft with their protrusion in the inner cavity of the shaft, while the elements 12 of the key 4 are made in the form of diametrically located protrusions 14. The protrusions 14 are located relative to the vertices "a" and "b" of the hexagon of the profiled head 11 at an angle

₁ . When this contacting surface of the protrusions 14 are located relative to the stops 13 piles with angular displacement (angle

₁ minus half the angular dimensions of the width of the protrusions 14 and stops 13).

задан центральным углом

₁ у паза 15 за вычетом центрального угла

₂ у диаметра стержня 17.In another example, the device 8 for receiving torque is made in the form of through oval grooves 15, diametrically located on the shaft 5 of the pile (figure 4). In this case, two diametrically located holes 16 are made in the upper part of the rod 9 of the key 4, and the torque transmitting elements 12 are a removable metal rod 17 installed in the combined (when the key 4 is installed in the pile cavity) holes 16 and grooves 15 , and the angle

defined by the central angle

₁ at groove 15 minus the center angle

₂ at the diameter of the rod 17.

To reduce the complexity of manufacturing the grooves 15, they are made in the shell 18, welded in the upper part of the barrel 5.

(фиг.3-4).When you insert the internal inventory key 4 into the cavity of the pile, it is installed so that the elements 12 for transmitting torque in the initial state are located relative to the device 8 of the torque sensing of the pile with an angular gap

(Figs. 3-4).

For the oriented placement of the inventory key 4 in the seat 7 on the pile and on the key 4, pointers 19 and 19 'are installed, made in the form of marks or marks.

The proposed method of immersion of a screw pile is as follows.

.The process of immersion begins with charging the working body of the machine with an inventory key 4. Head 10 is brought into the working body 2 of the machine. Then, using the pointers 19, install the inventory key 4 in the cavity of the pile 1 to a position where its profiled head 11 enters the seat 7, and the elements 12 of the key 4 are in the initial state relative to the devices 8 with an angular gap

.

риски 19 на стволе 5 сваи совмещают с рисками 19' на ключе 4, шестигранные посадочные поверхности ключа и сваи при этом совпадают и тем самым обеспечивается установка внутреннего инвентарного ключа относительно сваи на заданный угол

.According to the first embodiment of a screw pile (figure 3), the pointers 19 are located on the same axis with the stops 13. To provide the necessary angle of exhibition

the risks 19 on the shaft 5 of the pile are combined with the risks 19 'on the key 4, the hexagonal seating surfaces of the key and the piles are the same and this ensures the installation of an internal inventory key relative to the pile at a given angle

.

According to another embodiment of the pile (Fig. 4), when the internal inventory key 4 is inserted into the pile cavity, the shaped head 11 is placed in the seat 7 with the grooves 15 made on the pile table and the holes 16 made on the key 4 aligned, and then installed rod 17. To ensure both screwing the piles and unscrewing them with the maximum possible torque, the rod 17 is installed symmetrically with respect to the rounded edges of the oval groove 15.

The immersion of the pile 1 begins with the penetration of the guide cone into the soil under the influence of the axial force P of the working body 2 of the machine with its simultaneous screwing by transmitting torque to the blade 3 of the pile through the internal inventory key 4.

и прилагаемым моментом кручения, геометрическими размерами инвентарного ключа (диаметр и длина его стержня), определена как для торсиона по известной зависимости

увязывающей величину крутящего момента и угловую деформацию торсиона, в нашем случае стержня 9 ключа 4 (см., например, проектировочный расчет торсионов из кн. "Расчет и конструирование гусеничных машин" под ред. Н.А.Носова, Л., Машиностроение, 1970 г., формула (XII.5), с.457-459).With further immersion of the pile in the process of screwing it from the moment the load is applied to the internal inventory key 4 to the interaction of the elements 12 for transmitting torque (protrusions 14 or the rod 17) with the device 8 for receiving torque (stops 13 or grooves 15), the rod 9 of the inventory key experiencing torsion, while the relationship between the angle of twist

and the attached torsion moment, the geometric dimensions of the inventory key (diameter and length of its rod), is defined as for a torsion by a known dependence

linking the magnitude of the torque and the angular deformation of the torsion bar, in our case, rod 9 of key 4 (see, for example, the design calculation of torsion bars from the book "Calculation and construction of tracked vehicles" edited by N.A. Nosov, L., Mechanical Engineering, 1970 g., formula (XII.5), p. 457-459).

The plot of the distribution of torsion stresses (τ) arising in the pile shaft and in the inventory key when immersed by the claimed method is shown in Fig.5.

As can be seen from the diagram, the maximum torsional stresses (τ _max ) from the transmission of all the torque neither in the pile nor in the internal inventory key exceed the permissible torsional stresses [τ].

For comparison, the plot of stresses in the shaft of a screw pile, immersed without the use of an internal inventory key (Fig.6, 7), and the plot of stresses that occur in the pile shaft and internal inventory key when they are jointly immersed (Fig.8), but interacting with each other without the possibility of mutual angular movement (with this embodiment of the screw pile, the device for receiving torque is made not in the form of oval grooves, but in the form of holes whose diameter is equal to the diameters of the holes 16 and the rod 17), while in both in their cases, the torque applied to the pile shaft has the same meaning as in the claimed method.

In both cases, shown in Fig.7 and Fig.8, there is an excess of the maximum torsional stresses. So τ _max (in the pile shaft), see Fig. 7, significantly exceeds [τ]. This phenomenon also occurs in the second case, see Fig. 8, where τ _max1 (in the pile shaft) exceeds [τ _max ] although τ _max2 (in the core of the internal inventory key) is significantly less than [τ].

After immersion of the screw piles to a predetermined depth, the transmission of torque to the pile blade is stopped, the internal inventory key 4 is removed from the barrel 5 by drawing it into the working body 2 of the machine for screwing the piles.

Thus, the inventive method of immersing a screw pile into the ground together with the inventive device piles ensure the distribution of the torque transmitted from the machine, necessary for screwing the piles, into two components (first through the internal inventory key - as the first component, then, when the set torque value is reached , and through the pile shaft - as the second component). Thus, the claimed method of immersion and the design of the screw piles allow the implementation of the above torque transmission scheme and provide less material consumption in comparison with the prototype, which is a solution to the problem.

Claims (7)

1. A method of immersing a screw pile into the ground, including pressing the pile together with screwing it using an internal inventory key, characterized in that when screwing the pile the torque to the screw blade is initially transmitted using the inventory key, then as the resistance to screwing the pile increases, they are put into operation for transmitting torque to the pile shaft, while avoiding exceeding the set torque value both on the key and on the pile shaft. 2. The method according to claim 1, characterized in that the inclusion in the work of the shaft of the pile when the specified value of the torque on the inventory key is achieved is automatically ensured by the interaction of the elements of the inventory key transmitting torque and a device for sensing torque located on the pile, wherein said wrench is installed in a pile prepared for screwing in such a way that the torque transmitting elements of the inventory key in the initial state are located relative to itelno aforementioned device for sensing torque at an angular clearance Θ, which is determined from the relation

where MKR is the set value of the torque; G is the shear modulus of the material of the core of the internal inventory key; Iр - polar moment of inertia of the cross section of the rod of the internal inventory key; L is the length of the core of the internal inventory key. 3. A screw pile, including a cylindrical tubular barrel with a guide cone, a screw blade and a seat in the lower part of the barrel for an internal inventory key, characterized in that the pile shaft is made of metal and is equipped with a device for receiving torque from the above key in its upper part. 4. The pile according to claim 3, characterized in that the device for sensing torque is made with the possibility of interaction with transmitting torque elements of the inventory key upon reaching the set value of torque. 5. Pile according to any one of paragraphs.3 and 4, characterized in that the elements for the perception of torque are made in the form of stops mounted on its trunk with a protrusion into the internal cavity. 6. Pile according to any one of paragraphs.3 and 4, characterized in that the elements for the perception of torque are made in the form of through rounded grooves at the ends of the diametrically located on the trunk. 7. Pile according to any one of claims 3 to 6, characterized in that it contains pointers, for example, in the form of pictures or marks for the oriented location of the inventory key in its seat.

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