Method of installing screw piles and device for implementing method

Abstract

FIELD: petroleum engineering.SUBSTANCE: invention can be used to implement the claimed method for installing pile supports for oil well collectors, foundations and foundations in areas with soils of any hardness, including those with solid inclusions, in permafrost soils and soils with seasonal freezing. The method for installing screw piles in soils of any hardness, including permafrost, seasonal freezing, and soils comprising solid inclusions, involves drilling a pilot hole of the design diameter into the soil to the design depth and screwing a screw pile into it using a unit with a screwing mechanism with one or more blades arranged along a single helical line with a constant pitch and with any design of cutting elements along the perimeter. The screw pile is immersed into a pilot borehole by rotation together with the formation of a screw thread in the wall of the pilot borehole by the pile blades directly from the soil surface to the design depth of the borehole installation with full correspondence of the pitch and profile of the thread in the soil to the pitch and profile of the pile blades, ensuring stable proportionality between the immersion value and the angle of rotation of the pile until the complete completion of the immersion process, and the pile is immersed to the pitch of the screw pile by rotating it by 360 degrees. A device is used for implementing the method of installing a screw pile in soils of any hardness, equipped with a transmission-converting mechanism of the "screw-nut" type with a thread lead equal to the pitch of the helical line of the pile, wherein the nut of the transmission-converting mechanism is made fixed, and the screw and the pile, rigidly connected to each other, perform stable, functionally linked translational and rotational movements with the immersion of the pile in the soil with the simultaneous cutting of a thread in the wall of the leader borehole with a pitch and profile that fully correspond to the pitch and profile of the pile turns.EFFECT: increasing the bearing capacity and stability of piles in the design position by maintaining the integrity of the soil from its surface to the design depth and by making a thread in it with a profile and pitch that fully correspond to the pitch and profile of the pile blades and by reducing the stress-strain state of the pile during installation.4 cl, 1 dwg

Description

[0001] The invention relates to petroleum engineering and can be used to implement the claimed method for installing pile supports for oil well collectors, foundations and foundations in areas with soils of any hardness, including those with solid inclusions, in permafrost soils and soils with seasonal freezing.

[0002] A known method involves inserting the lower end of a helical pile shaft into a pre-drilled pilot hole and screwing it into the ground to the design depth of the helical blade at the bottom of the shaft. The pilot hole is drilled with a diameter equal to the diameter of the cylindrical portion of the pile. With this type of penetration, there is no drag from the lower end; the helical blades cut through the hard, frozen soil, and the pile shaft passes through the pilot hole without resistance (Irodov, M.D., Use of Screw Piles in Construction. Stroyizdat. Moscow-Leningrad, 1968, p. 15).

[0003] The disadvantage of this method is that it does not guarantee that the pile will form a screw thread in the soil, especially when penetrating surface soil layers. This is due to insufficient or excessive axial force applied to the pile. This force determines the speed of pile penetration into the pilot borehole, compared to the force required to ensure proportionality between the pile's axial displacement and its angular displacement, which is a prerequisite for thread formation. If the axial force is insufficient, the pile blades will drill into the soil, forming an unthreaded cylindrical borehole with a diameter equal to the overall diameter of the blades. If the axial force is excessive, along with residual deformations, the blades will push through the soil, forming an unthreaded shaft above them in some part of the borehole. In both cases, the pile's load-bearing capacity and its stability in the required design position will be reduced.

[0004] A known method (Patent No. 2117098C1, IPC E02D 5 / 56, 7 / 22, published 10.08.1998, Bulletin No. 22) includes the formation of a weakening zone along the installation axis and screwing in a screw support. Weakness zones are formed by loosening the soil without removing it to the surface, wherein the weakening zone in medium-density soils is made with a diameter smaller than the diameter of the screw blade of the support by its double width, and in dense and frozen soils - with a diameter equal to or greater than the diameter of the screw blade by an amount equal to its double width, while the depth of the weakening zone is taken equal to the design depth of the screw support.

[0005] The disadvantages of this method, regardless of the initial soil hardness, include damage to the soil integrity in the contact zone and the formation of a threadless cylindrical section in the borehole due to reaming or soil pushing due to the lack of a kinematic relationship between the axial penetration and the pile rotation angle necessary to form a thread with a constant pitch. The consequence of both disadvantages is a reduction in the pile's bearing capacity and its stability in the designed position.

[0006] The closest method for installing screw piles (the prototype) is the method described in patent RU No. 2786081 C1, which includes drilling a cylindrical borehole (leader) of the required depth with a drilling mechanism with a crown, while simultaneously cutting a thread in the ground or in the form of a separate technological operation for cutting a thread in the leader borehole and installing a screw pile by screwing it along this thread.

[0007] A disadvantage of this method, with either of the two thread cutting options in the pilot borehole wall, is the complete or partial disruption of the soil integrity, depending on the real-time discrepancy between the applied axial force and the soil hardness. If the axial force is insufficient, the cutting tool will drill a new borehole from the pilot borehole with a diameter equal to the cutting tool's diameter, without forming a thread in the soil, starting from the ground surface. If the applied axial force exceeds the required value, then, at best, a thread with a variable pitch and profile will form in the soil, exceeding the pitch and profile of the helical pile blades due to partial soil compression, or, at worst, a threadless cylindrical shaft. In all of these cases, the load-bearing capacity and stability of the pile in its intended position will not meet the requirements of the technical documentation.

[0008] The disadvantage of the installation implementing this method, which consists of a mobile platform and a drilling mechanism comprising a moving part with a shaft and an auger with cutters on its periphery that cut threads in the ground, is that it does not solve the problem of real-time matching of the applied axial force with the required force for a given soil hardness to form a thread that fully replicates the helical pitch and blade profile of the driven screw pile. As a result, the pile will have reduced bearing capacity and stability in its intended position.

[0009] A device for driving screw piles is known (patent No. 61732, IPC E02D 7 / 22), which we have adopted as a prototype, consisting of a base machine, on the platform of which a crane-manipulator with a mechanism for screwing piles is mounted, containing a rotator, a gearbox and a chuck for securing the pile in it.

[0010] A disadvantage of this device is the lack of a mechanism to ensure the pile is driven by the pitch of its helical line, rotating 360 degrees from the start of its penetration into the pilot hole to the completion of its penetration to the design depth. Inconsistency in these movements, especially typical in soils with varying density and those containing solid inclusions, leads to damage to the soil integrity due to drilling or pushing, and, consequently, to a reduction in the pile's bearing capacity and its stability in the design position.

[0011] The technical problem solved by the proposed invention is the creation of a method for driving screw piles into soils of any hardness, including those with solid inclusions, into permafrost soils and with seasonal freezing, and a device for implementing this method with the achievement of the following results: increasing the load-bearing capacity of piles and stability in the design position by maintaining the integrity of the soil and forming a screw thread in the soil along the entire depth of the pilot borehole, starting from the surface with a profile and pitch that fully correspond to the profile and pitch of the pile blades.

[0012] The said technical results are achieved by the fact that in the method of driving screw piles into soils of any hardness, including permafrost, with seasonal freezing, with solid inclusions, which consists in drilling a leader borehole of the calculated diameter into the soil to the design depth, screwing into it with a unit with a screwing mechanism of a screw pile with one or more blades placed along a single helical line with a constant pitch and with any design of cutting elements on the perimeter, according to the invention, driving a screw pile into a leader borehole by rotation is carried out together with the formation by the blades of the pile of a screw thread in the wall of the leader borehole directly from the surface of the soil to the design depth of installation of the pile with full compliance of the pitch and profile of the thread in the soil with the pitch and profile of the blades of the pile, ensuring stable proportionality between the amount of immersion and the angle of rotation of the pile until the complete completion of the process diving,whereby the pile is driven in by the value of the helical pitch by turning it 360 degrees.

[0013] The method is implemented using a device for installing screw piles by screwing and threading a pilot hole. The device comprises a base platform mounted on a chassis of any design, a crane manipulator, a rotary unit, and a gearbox, which is additionally equipped with a "screw-and-nut" transmission mechanism with a thread lead equal to the helical pitch of the pile. The housing of the transmission mechanism, with a fixed nut located within it, is connected to the base platform via a telescopic support boom with a locking device for its extension. The screw is coupled to the gearbox output shaft via a clutch, and to the pile being driven via a chuck, and performs rotary-translational, functionally linked movements, transmitting these movements to the pile.The telescopic support boom's connections to the transmission-conversion mechanism housing and the base platform are articulated and equipped with locking devices that ensure the transmission-conversion mechanism is firmly secured at the required height and in the designed position of the screw-pile assembly axis relative to the ground surface and the pilot bore axis, respectively. Furthermore, the device for forming the thread in the pilot bore and screwing in the pile is equipped with one or more inserts with a length equal to the screw's working stroke, with one end of the insert being identical to the shape of the pile head, and the other end equipped with a chuck.

[0014] The figure shows a diagram of a device for forming a thread in a pilot hole and screwing in a pile to implement the claimed invention.

[0015] The device according to the claimed invention comprises a base platform 1 mounted on a chassis of any design, a crane-manipulator 2 with a rotator 3 and a gearbox 4 fixed thereto, a transmission-converting mechanism 5 including a housing 6 with a fixed nut 7 fixed inside, a screw 8, a cartridge 9 and a coupling 10 for connecting the screw 8, respectively, with a pile 11 and an output shaft of the gearbox 4, a support telescopic boom 12 with a lock 13 of the extendable part in the required position, wherein the connection of the support telescopic boom 12 with the base platform 1 and the housing 6 of the transmission-converting mechanism 5 is made with the help of, respectively, hinges 14 and 15 with locks 16 and 17 fixing the telescopic support boom 12 and the transmission-converting mechanism 5 in the working positions.

[0016] The screw pile installation device works as follows.

[0017] Due to the telescopic design of the boom 12 and the articulated joints 14 and 15 of the boom 12 with the base platform 1 and the body 6 of the transmission-conversion mechanism 5, the pile 11 is brought to its initial position relative to the pilot hole before the implementation of the method is started. Then, the rotator 3 of the crane-manipulator 2 is started, causing the rotation of the output shaft of the gearbox 4 and, accordingly, the screw 8 and the screw pile 11. Due to the immobility of the nut 7 due to the rigid connection of the body 6 with the base platform 1, the rotating screw 8 simultaneously performs a translational motion, imparting a similar motion to the screw pile 11, due to which the screw pile 11 is driven into the ground, forming a thread in the ground.Due to the structurally implemented equality of the thread stroke (pitch) of the transmission-converting mechanism 5 to the pitch of the screw pile 11, the immersion of the screw pile 11 by the value of each of its pitches is carried out automatically by rotating the screw pile 11 by 360 degrees, since in the “screw-nut” transmissions the two movements are functionally linked, i.e. they cannot be carried out separately from each other.

[0018] In this case, nut 7 prevents the rocking of screw pile 11 during the immersion process and in real time ensures equality of the soil resistance force to the immersion of pile 11 into it and the axial load on the section of screw 8 from pile 11 to nut 7, regardless of the axial load created by the crane-manipulator.

[0019] If the crane-manipulator generates an axial force greater than that required to overcome the soil's resistance to driving, the difference in these forces will be transmitted through nut 7, body 5, and telescopic boom 12 to platform 1, forming a closed system of forces. If the axial force generated by the crane-manipulator is insufficient, the missing axial force for pile driving will be generated in the screw-nut drive thread due to the torque of the gearbox shaft, in accordance with the known ratio of axial to circumferential force in the thread.

[0020] If the working stroke of the screw of the transmission-conversion mechanism is insufficient for driving the pile to the design depth, an insert with the specified design of the ends is installed between the screw, retracted to the upper extreme position, and the pile being screwed in, and the rotary device is turned on, continuing the process of driving the pile into the leader hole.

[0021] The technical and economic advantage of the proposed method of driving piles into the ground is an increase in the bearing capacity and stability of the piles in the design position due to maintaining the integrity of the soil from its surface to the design depth and making a thread in the ground with a profile and pitch that fully correspond to the pitch and profile of the pile blades, regardless of the hardness and granulometric composition of the soil, a reduction in the stress-strain state of the pile during driving due to the elimination of overloading by axial force from the crane-manipulator.

Claims

1. A method for installing screw piles in soils of any hardness, including permafrost, seasonally frozen soils, and soils containing solid inclusions, which consists of drilling a pilot hole of the design diameter into the soil to the design depth, screwing a screw pile into it using a unit with a screwing mechanism with one or more blades arranged along a single helical line with a constant pitch and with any design of cutting elements on the perimeter, characterized in that the immersion of the screw pile into the pilot hole by rotation is carried out simultaneously with the formation of a screw thread in the wall of the pilot hole by the pile blades directly from the soil surface to the design installation depth of the hole with full correspondence between the pitch and profile of the thread in the soil and the pitch and profile of the pile blades, ensuring stable proportionality between the immersion value and the rotation angle of the pile until the immersion process is completely completed,wherein the immersion of the pile to the value of the pitch of the screw pile is carried out by rotating it by 360 degrees, while using a device for implementing the method of installing a screw pile in soils of any hardness, equipped with a transmission-converting mechanism of the "screw-nut" type with a thread lead equal to the pitch of the helical line of the pile, wherein the nut of the transmission-converting mechanism is made fixed, and the screw and the pile, rigidly connected to each other, perform stable functionally linked translational and rotational movements with the immersion of the pile in the soil with the simultaneous cutting of a thread in the wall of the leader borehole with a pitch and profile that fully correspond to the pitch and profile of the pile turns.

2. A device for implementing a method for installing screw piles in soils of any hardness, including permafrost, seasonal freezing, and solid inclusions, comprising a base platform mounted on a chassis of any design, a crane-manipulator, a rotator, and a gearbox, characterized in that it is equipped with a transmission-converting mechanism of the "screw-nut" type with a thread lead equal to the pitch of the helical line of the pile, wherein the housing of the transmission-converting mechanism with a fixed nut located therein is connected to the base platform by means of a telescopic support boom with a lock for its extension, the screw is connected to the output shaft of the gearbox by means of a clutch, and to the pile being driven - by means of a chuck and performs rotational-translational functionally linked movements with the transmission of these movements to the pile.

3. A device for implementing the method for installing screw piles according to paragraph 2, characterized in that the connections of the telescopic support boom with the body of the transmission-conversion mechanism and with the base platform are made articulated and equipped with clamps that ensure rigid fixation of the transmission-conversion mechanism at the required height and in the design position of the axis of the screw-pile complex relative to the ground surface and the axis of the pilot borehole, respectively.

4. A device for implementing the method for installing screw piles according to paragraph 2, characterized in that the transmission-conversion mechanism is equipped with one or more inserts, each with a length equal to the working stroke of the screw, wherein one end of the insert is made identical to the shape of the pile head, and the other is equipped with a cartridge.

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