RU2385383C1 - Working member for device of screw bored piles - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: working member for device of screw bored piles consists of casing pipe, shoe with screw blade and a tip and is sunken in the soil by being screwed by applied torque moment and axial vertical force. Working member differs by the fact that a cone-shaped tip has sharpness angle of 90°, inclination angle of screw line of the blade is chosen as per the given formulas for ensuring rational values of force impacts from the submerging mechanism, there is tight demountable joint of casing pipes, shoe has the radius which is more than that of casing pipe, which is chosen from the given equation, owing to which soil pressure is relieved to casing pipe due to recovery of elastic soil deformation after introduction of the shoe. When the working member is submerged, the soil is expanded with a shoe to sides, thus being compacted. When design reference mark is reached, reinforcement cage is installed in casing pipe, and pile is concreted with simultaneous removal of the working member by unscrewing and rotating it in opposite direction; at that, the tip remains in the soil. By means of the above, soil is compacted once again, and cavities left with the shoe are filled with concrete.

EFFECT: considerable decrease of power consumption required for well erection process.

1 cl, 3 dwg

Description

The invention relates to the field of construction, namely to foundation engineering, and can be used both in the construction of new and in the strengthening of the foundations of previously constructed buildings and structures, as well as in the construction of supports accepting alternating loads.

A known method of construction of piles (RF patent 2317373, E02D 5/56, 01/30/2007), which consists in the formation of a pilot well in the soil by drilling and issuing the destroyed soil to the surface by means of a hollow screw drill with a rock cutting tool, placing a metal frame in the well, filling its concrete and cuts in the walls of the pilot hole of the helical gap.

The disadvantage of this method is the low bearing capacity of the piles due to decompression of the walls of the well and thixotropic softening in the case of the device piles in dusty clay soils.

A known method of manufacturing piles (RF patent 2278212, E02D 5/56, 5/36, 04/01/2005), which consists in the formation of a well in the soil due to forced displacement of the soil using a drill string with a tip consisting of conically and cylindrical rigidly connected to each other rollers that are left in the well.

The disadvantage of this method is the high cost and the complexity of manufacturing each left in the soil tip.

The closest in technical essence is a method of manufacturing piles (RF patent 2076173, E02D 5/56, 5/36, 05/05/1995), which consists in immersing under the influence of rotation forces and axial feeding into the ground of a hollow tip with a screw protrusion on it and a tubular rod and supplying reinforcement and concrete through the upper hole of the rod at the same time as removing the rod from the ground.

The disadvantage of this method is the use of a lost tip, a helical shoe and a blade of irrational shape that increase the energy intensity of well production, the presence of a gap between the shoe and the tubular rod, into which water and soil get in the case of making piles in water-saturated soft soils, as well as complexity, laboriousness and large the cost of manufacturing the entire working body, the unreliability of its work in weak water-saturated soils.

The objective of the invention is to reduce the energy intensity and cost of the device piles by optimizing the structural parameters of the working body and simplifying its manufacture, as well as increasing its reliability through the use of new design solutions.

The technical result is achieved by the fact that the working body, containing the lost tip, shoe with a helical blade and the casing, has a lost tip with a sharpening angle of 90 degrees, which is justified by the research and leads to minimal energy consumption during the construction of the pile (formula for determining the work of the torque acting on the lost by the tip (1) wherein M ₁ - torque required for immersing the tip into the ground; R - radius of the shoe, and - pitch propeller blades; β - half the tapering tip angle; - height of the shoe; h - the height of the casing), a helical blade which has an angle of helix, through which an optimal distribution of the torque and the vertical force on immersion mechanism (the formula (2) to determine

torque and (3) to determine the vertical force acting on the helical blade, where C ₁ is the coefficient of total deformation of the soil; a is the angle of sharpening of the blade; B is the width of the blade; µ is an exponent; n is the number of turns of the blade; γ is the angle of inclination of the helical line of the blade; f is the friction coefficient), a shoe having a radius greater than the radius of the casing ((4), where C ₂ is the coefficient of elastic deformation of the soil), due to which the soil pressure on the casing is removed due to the restoration of elastic deformation of the soil after the shoe is inserted into it, therefore, significantly reduces the magnitude of the torques and vertical forces necessary for immersion of the working body, and the joint, providing tightness, collapsibility and simplicity of the process of increasing the length of the working body.

The invention is illustrated in the drawing, where in Fig. 1 it is indicated: 1 - a lost conical tip, 2 - a shoe, 3 - a helical blade, 4 - a lower section of a casing pipe, 5 - a pipe, 6 - a plug, 7 - a stackable section of a casing.

Explanation for example of determining the helix angle

In formulas (2) and (3), the angle of elevation of the helix and the magnitude of the torque and vertical force are unknown. Parameters C ₁ , f and µ are found by testing in the laboratory soil samples obtained as a result of engineering and geological work at the construction site (well drilling). The angle of sharpening of the blade a is determined by preliminary static calculation of the blade for strength under the action of building and operational loads by methods of building mechanics. The number of turns of the blade is taken to be 1.25, since this ensures the minimum energy consumption of the well manufacturing process, which is justified by numerous studies by L.L. Bogorad, M.D.Irodov, V.A. Penchuk, I.I. Tsyurupy, I.M .Chistyakova and other authors. The radius of the shoe and the width of the blade are the parameters that determine the diameter of the pile being built, which, in turn, must be found previously using SNiP 2.02.03-85 “Pile foundations” by calculating the pile foundation for design loads.

At the next stage, you need to set the helix angle (for example, 10 degrees), substitute all the values in formulas (2) and (3) and determine the torque and vertical force.

The following describes the characteristics of the immersion mechanism. If the mechanism is not able to provide sufficient torque, but provides sufficient vertical force, the angle of elevation of the helical line is adjusted upward, and recalculation is performed. In the event that the mechanism is not able to provide sufficient vertical force, but provides sufficient torque, the angle of elevation of the helical line is adjusted in a smaller direction, and recalculation is performed. In the event that neither sufficient vertical force nor sufficient torque is provided, it is necessary to replace the immersion mechanism with a more powerful one or redesign the working body.

The working body consists of a lost conical tip 1, shoe 2 with a helical blade 3, sections of the casing 4 and 7 and joints. The screw shoe is rigidly connected to the casing to prevent soil and water from getting inside the casing, to transfer torque the lost tip is provided with protrusions, to prevent horizontal displacement, the inner shell (figure 2). The developed joint of casing pipes allows to produce piles of any length within the power of the immersion mechanism. The joint includes protrusions on both edges of the connected pipes for transmitting torque, an additional tubular pipe 5 (Fig. 3), welded to the top of the lower section of the pipe and into which the bottom of the upper section is inserted to prevent lateral displacement of the sections, plugs 6, inserted into the holes in the nozzle and the immersion section for transmitting tensile force when unscrewing the working body. This ensures the sealing of the working body, the exclusion of the entry of soil and water into the manufactured piles, which means that it becomes possible to build piles in flooded soft soils. The design of the working body is easy to manufacture and use and reliable.

The working body is immersed in the ground by screwing. When immersed, the surrounding soil is pushed apart by the shoe to the sides, thereby compacting. Upon reaching the design mark, a reinforcing cage is inserted into the casing, and the piles are concreted with simultaneous extraction of the working body by unscrewing it by rotating it in the opposite direction, while the lost tip remains in the ground. With this, the soil is compacted once more, and concrete fills the voids left by the shoe.

Claims (1)

The working body for the manufacture of screw pile, including casing, shoe with a helical blade and a lost conical tip, characterized in that the lost tip is made with a sharpening angle of 90 °, the angle of inclination of the helical line is selected based on the above formulas (2), (3) , the shoe has a radius greater than the radius of the casing, selected from the above equation (4), as well as a sealed joint of the casing, equipped with a sealed pipe welded to the top of the lower section of the pipe, and plugs.

where M ₃ - torque required for immersion of the working body in the ground, kNm; P ₃ - vertical force required for immersion of the working body in the ground, kN; r is the radius of the casing, m; R is the radius of the shoe, m; C ₁ - coefficient of total soil deformation, kN / m ³ ; α is the angle of sharpening of the blade, deg; B - blade width, m; µ is an exponent; n is the number of turns of the blade; γ is the angle of inclination of the helix of the blade, deg; f is the coefficient of friction; C ₂ - coefficient of elastic deformation, kN / m ³ .

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