RU2327007C1 - Method of drill-injection stilt formation - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method includes consistently following technological operations: in the beginning the pilot hole is drilled to design depth by the hollow, tight boring reciprocating screw supplied in its bottom part with a bar chisel with a slip sliding valve and inbuilt ink-jet monitors, with adjustable rotation speed of a boring reciprocating screw to 60 rpm, clockwise, then, having increased rotation speed of a boring reciprocating screw to 120 rpm by means of inbuilt ink-jet monitors, design quantity of a water cement mix is delivered by directed jets under the set high pressure not less than 6 MPa, than scour a ground and create below widening of pilot hole from a soil-cement mix due to vertical, back and forth motion of a rotating boring reciprocating screw, thus, the amplitude of back and forth motions of a boring reciprocating screw corresponds to the set design height of created widening of a pilot hole, and the total amount of a delivered water-cement mix in a hole should not be more than it one-and-a-half-fold size, then a slip sliding valve in a bar chisel is opened and, with rotating of a boring reciprocating screw counter-clockwise with a speed no more than 60 rpm, lifting of a boring reciprocating screw on height equal to a double spacing of a reciprocating screw flange is carried out, and only after that, under a reduced pressure of 0.5 MPa through a slip sliding valve the fine-grained concrete is delivered and simultaneously the back and forth motions of a boring reciprocating screw is carried out, with amplitude equal to a widening height till the moment of the beginning of the fine-grained concrete outcropping from a hole mouth, then a boring reciprocating screw is taken out without rotation and simultaneously the fine-grained concrete is delivered under the pressure of 0.15 MPa, a prefabricated reinforcement cage is set in a hole, the fine-grained concrete is moulded in a hole by the pressure not less than 0.15 MPa, thus the fine-grained concrete volume should exceed the water cement mix volume delivered to a hole not less than on 10%.

EFFECT: new method of drill-injection stilts formation.

3 cl, 4 dwg

Description

The invention relates to the field of construction, mainly to the technology of construction of foundations and foundations.

A known method of device injection piles (1), including drilling a well, installing a reinforcing cage in the well, filling the well with cement mortar, crimping the pile shaft.

The closest technical solution, selected as a prototype, is a method of forming a bored pile (2), which involves introducing a continuous hollow screw into the soil, mainly by screwing it to the design depth and then extracting it and simultaneously supplying concrete mixture through the cavity under the end part of the screw and immersing in concrete mix of metal reinforcing cage. The disadvantages of the known methods include the insufficient bearing capacity of piles obtained by the implementation of known methods.

The objective of the invention is to increase the bearing capacity of piles, ensuring its reliability and durability.

This is achieved by the fact that in the method of formation of the injection pile, including the introduction of a continuous hollow screw into the soil, mainly by screwing it to the design depth and then removing it and simultaneously supplying concrete mixture through the cavity in the screws under the end part of the screw and immersing the reinforcing cage into the concrete mixture, according to the invention, the leader hole is first drilled to the design depth with a hollow sealed auger equipped with a slide bit with a sliding spool in its lower part and jet monitors, with an adjustable rotation speed of the drill auger up to 60 rpm clockwise, then, increasing the rotation speed of the drill auger up to 120 rpm, through the built-in jet monitors they feed water-cement mixture under a given high pressure of at least 6 MPa, what erodes the soil and creates below the broadening of the leader well from the cement mixture due to the vertical, reciprocating movement of the rotating drilling auger, while the amplitude of the reciprocating movements of the bu a straight screw corresponds to a given design height of the created broadening of the leader well, and the total volume of water-cement mixture supplied to the well should not exceed its size one and a half times, then a sliding spool in the bar bit is opened and, rotating the drill auger counterclockwise at a speed of no more than 60 rpm, they raise the drilling auger by an amount equal to the double pitch of the auger flanges, and only then, under reduced pressure of 0.5 MPa, fine-grained concrete is fed through a sliding spool and at the same time the reciprocating movements of the drill auger with an amplitude equal to the height of the broadening are taken until the beginning of the exit of fine-grained concrete from the wellhead, then the drill auger is removed without rotation and at the same time fine-grained concrete is fed under a pressure of 0.15 MPa, the reinforcing cage is installed in the well, crimping is performed fine-grained concrete in the well with a pressure not lower than 0.15 MPa, while the volume of fine-grained concrete should exceed the volume of water-cement mixture supplied to the well by at least 10%. In this case, inkjet monitors are placed between the blades of the bar bit, directly behind the rock cutting tool and are embedded in such a way that the projections of the longitudinal axes of the inkjet monitors on a horizontal plane are inclined to the radii of the inscribed circle of the bar bit at an angle of 110-120 degrees, and on a vertical plane at an angle of 30 degrees to the vertical, and the direction of the jet coming out of the built-in monitors coincides with the direction of rotation of the drill auger.

Made by the proposed method, the pile has increased bearing capacity, reliability and durability due to the fact that the diameter of the lower end of the pile exceeds the diameter of the pile shaft, which means that the frontal resistance of the pile with broadening exceeds that for a pile without broadening. In addition, when cutting a pile in bulk or subsidence soils, the presence of a thinner (compared to broadening) pile shaft leads to a decrease in negative friction forces, and the presence of broadening increases the drag under the lower end of the pile, which in such conditions leads to an increase in the bearing capacity of the pile .

The proposed method of formation of injection piles with the removal of cuttings to the surface using a high-pressure water-cement mixture allows to increase the diameter of the pile shaft, which leads to an increase in its bearing capacity and to an increase in the protective layer of concrete, and therefore to an increase in the durability of the pile, because an increased protective layer concrete protects reinforcement from corrosion. The amount of water-cement mixture supplied for erosion of the broadening of the well is determined by the volume not exceeding one and a half times the initial volume of the well, so that with the most frequently encountered: length of injection piles up to 20 meters and diameter of piles up to 0.25 meters effective, from the point of view of increasing the bearing capacity of piles , the broadening diameter should not be more than 0.4 meters. Built-in monitors in the bar bit, and not in the auger string, allow a high-pressure jet to act directly on the soils in the bottom of the well and form a broadening with no drill cuttings beneath it. In addition, the built-in monitors in the bar bit with a movable spool simplify the design of the inkjet installation and the technology of work, as allow one cavity to be used both for a high-pressure jet and for the subsequent supply of fine-grained concrete into a pile. And the installation of inkjet monitors in such a way that the projections of the longitudinal axes of the inkjet monitors on a horizontal plane are inclined to the radii of the inscribed circle of the movable bar bit at an angle of 110-120 degrees, and on a vertical plane at an angle of 30 degrees to the vertical allows the column of screws to be washed out by base down cone. This facilitates erosion of the soil and the removal of cuttings to the surface. In addition, the direction of the jet tangent to the horizontal projection of the bit allows you to increase the energy of the jet emitted under pressure from the water-cement mixture due to the kinetic energy of the centrifugal acceleration of the rotating augers. In addition, the transition between the pile shaft and the broadening has a conical shape, which makes it possible to transfer the load from its trunk to the broadening more effectively without stress concentration during the operation of the pile.

The use of counterclockwise rotation of the drill auger when fine-grained concrete is fed in makes it possible to add forced pressure of fine-grained concrete to the pumping pressure by forcing it to move downward when turning counterclockwise (similar to the way minced meat is squeezed out of a meat grinder), which leads to the complete filling of all cavities in broadening. The presence of a gap between the auger and the borehole wall, formed when the water-cement mixture was removed from the broadening erosion, allows fine-grained concrete to leak to the surface under the influence of pumping pressure and forcing it to move downward when the drill auger rotates counterclockwise.

The proposed technical solution is illustrated by drawings, in which Fig. 1 shows the stage of formation of a leader well and broadening with a screw auger, Fig. 2 shows a drilling injection pile made by the claimed method, Fig. 3 is a section A-A, and Fig. 4 is a section Bb.

The method of formation of injection piles is as follows. Initially, the leader hole (1) is drilled to the design depth with a hollow sealed auger screw (2) with an adjustable rotation speed of up to 60 rpm. The drill auger (2) is equipped in its lower part with a bar bit (3) with a movable slide valve (valve) and jet monitors (4) built into its body, the projections of the longitudinal axes of which on a horizontal plane are inclined to the radii of the inscribed circle of the movable bar bit at an angle of 110 -120 degrees, and on a vertical plane at an angle of 30 degrees. Inkjet monitors (4) are mounted on a sliding bar bit (3) behind the rock cutting tool (5). Then, increasing the speed of rotation of the drill auger (2) to a value of at least 120 rpm in the clockwise direction, a water-cement mixture is fed through the cavity in the augers to the jet monitors at an initial high pressure of at least 6 MPa and creates a broadening with such a wash (6) in the lower part of the leader well (1) by vertical reciprocating movements of the drill auger (2). The total volume of water-cement mixture supplied to one well should not exceed its size one and a half times. The amplitude of the reciprocating movements of the drill auger (2) should correspond to a given height (h) of the formation of broadening in the lower part of the leader well (1). Due to the erosion of the soil by directed rotating and moving “down-up” jets of the water-cement mixture in the lower part of the well, a cavity is created - a broadening (6), filled with a mixture of eroded soil and a water-cement mixture. The water-cement mixture is supplied to the monitors until one of the conditions is reached: before the beginning of the exit from the mouth of the leader well (1) of the mixture of washed soil and water-cement mixture or until the volume of the supplied water-cement mixture reaches one and a half times the volume of the leader well (1). After that, open the slide valve on the bar bit (4) and, rotating the drill screw (2) counterclockwise at a speed of 60 rpm, lift the drill screw (2) by an amount (1) equal to the double pitch of the screw flange, and feed fine-grained concrete under hollow screws under a reduced pressure of 0.5 MPa compared to the initial pressure of 6 MPa. After opening the spool, at the same time as fine-grained concrete is fed, reciprocating movements are again performed by the drill auger (2) with an amplitude equal to the broadening height (h), while the drill auger (2) is rotated counterclockwise at a speed of 60 rpm to full substitution and displacement on the surface of the mixture of eroded soil and water-cement mixture and the beginning of the exit from the mouth of the leader well (1) of pure fine-grained concrete. After that, the drilling auger (2) is removed without rotating it and at the same time fine-grained concrete is fed under a pressure of 0.15 MPa and installed in the leader well (1) filled with fine-grained concrete, the reinforcing cage (7) and fine-grained concrete is pressed in the well by pressure below 0.15 MPa.

Information sources

1. Patent of Russia No. 2148124, cl. E02D 5/46, 2000.04.27.

2. Patent of Russia No. 2127345, cl. E02D 5/36, 1999.03.10.

Claims (3)

1. The method of formation of injection piles, including the introduction of a continuous hollow auger into the soil by screwing to the design depth and then removing it through the cavity of the concrete mixture and immersing the reinforcing cage into the concrete mixture, characterized in that the leader hole is drilled to the design depth hollow at first a drill auger with a bar bit made in its lower part with a movable spool and built-in inkjet monitors, with an adjustable speed of rotation of the auger up to 60 rpm clockwise, then increase the speed of rotation of the drill auger to 120 rpm./min, using jet monitors feed the calculated amount of water-cement mixture under pressure of at least 6 MPa with directional jets and perform a reciprocating movement of the rotary drill auger to erode the soil and create a bottom leader hole the broadening of the cement mixture, while the amplitude of the reciprocating movements of the drill auger corresponds to a given design height of the created broadening of the leader well, and the volume of water-cement mixture supplied to the well should not exceed its size one and a half times, then slide the spool in the bar bit and, rotating the drill auger counterclockwise at a speed of not more than 60 rpm, lift the drill auger by an amount equal to twice the auger flange pitch, and only after that, under a pressure of 0.5 MPa, a fine-grained concrete mixture is fed through a sliding spool and at the same time reciprocating movements of the drill auger with an amplitude equal to the height of the broadening until the beginning running on the surface of the fine-grained concrete mixture from the wellhead, then the drill auger is removed without rotation and at the same time the fine-grained concrete mixture is fed under pressure of 0.15 MPa, the reinforcing cage is installed in the well, the fine-grained concrete mixture is pressed in the well with a pressure of at least 0.15 MPa, the volume of fine-grained concrete mixture must exceed the volume of water-cement mixture supplied to the well by at least 10%. 2. The method of forming injection piles according to claim 1, characterized in that they use inkjet monitors that are embedded in the bar bit so that the projections of the longitudinal axes of the inkjet monitors on a horizontal plane are inclined to the radii of the inscribed circle of the bar bit at an angle of 110-120 °, and on a vertical plane under the corner 30 ° to the vertical. 3. The method of formation of injection piles according to claim 1, characterized in that the direction of movement of the jet emerging from the built-in monitors coincides with the direction of rotation of the drill auger.

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