RU2018130325A - MULTI-FOB SCREW PILES (OPTIONS) - Google Patents

Claims (18)

1. A multi-blade screw pile, designed to work in melt soils, consists of a shaft, one or more extension rods connected to the barrel and the head of at least one screw blade and fasteners, characterized in that the blades are located along the entire length of the barrel without limitation from the tip to the tip, the conical tip of the barrel is cut at an angle of 45 ° to the horizontal plane, the blades are selected of the same size, and the diameter of the blades is determined from 1.5D to 3.0D, where D is the diameter of the borehole and, the minimum length of the pile depends on the length of its screw part and the layer of seasonal freezing / thawing and is selected as a multiple of 0.5 meters, while the bearing capacity F _d (t) of the screw pile in thawed soils with a blade diameter d and a length L working on compressive or pulling load is determined by the formula F _d = γ _c (F _d0 + F _df ), where γ _c is the coefficient of the pile working conditions, depending on the type of load acting on the pile and soil conditions: F _d0 is the bearing capacity of the blade, tf, F _df - bearing capacity of the barrel, hardware, bearing capacity of the blades of a screw pile calculated according to the formula F _do = (α ₁ c ₁ + α ₁ γ ₁ h ₁ ) A, where α ₁ , α ₂ are dimensionless coefficients taken depending on the calculated value of the angle of internal friction of the soil in the working area ϕ ₁ (under the working area is understood to be a soil layer adjacent to the blade with a thickness equal to d), c ₁ is the calculated value of the specific adhesion of the soil in the working area, t / m ² , γ ₁ is the average calculated value of the specific gravity of the soils lying above the pile blade, t / m ³ , h ₁ - the depth of the pile blade from the natural topography, and when planning the territory by cutting - from the level of planning , m, A is the projection of the area of the blade, m ² , counting according to the outer diameter, when the screw pile is working on a compressive load, and the projection of the working area of the blade, i.e. minus the borehole cross-sectional area, when the screw pile is operated on a pulling load,

the formula for the projection of the area of the first blade for calculation of compression,

- the projection of the blades for calculation of pulling out, as well as the other blades for compression, the bearing capacity of the shaft of a screw pile is determined by the formula: F _df = uƒ _i (hd), where u is the perimeter of the cross section of the pile shaft, m, ƒ _i is the design resistance soil on the lateral surface of the shaft of the screw pile, tf / m2, (average value for all layers within the depth of the pile), h is the length of the shaft of the pile immersed in the soil, m, d is the diameter of the pile blade, m, u = π⋅d - the formula of the perimeter of the cross section of the pile shaft. 2. A pile according to claim 1, characterized in that the extension rod is connected to the barrel by means of a sleeve made in the form of a cylinder. 3. A pile according to claim 1, characterized in that the extension rods are selected in lengths of 3 and 6 meters. 4. Pile according to claim 2, characterized in that the coupling is fixed to the barrel by welding to an extension rod and by means of bolts with nuts. 5. Pile according to claim 2, characterized in that the immersion depth of the coupling is at least 2 meters. 6. The pile according to claim 1, characterized in that for thawed soils, the diameter D of the pile shaft is selected in the range from 89 mm to 426 mm. 7. A pile according to claim 1, characterized in that the number of blades of the same size is selected from 1 to 5. 8. A pile according to claim 1, characterized in that the distance between the turns of the blades (dies) with blade diameters from 400 mm to 1000 mm and higher is determined in the range from 75 mm to 225 mm. 9. A multi-blade screw pile, designed to work in permafrost soils, consists of a shaft, one or more extension rods connected to the barrel and head of at least one screw blade and fasteners, characterized in that the conical tip of the barrel is cut under at an angle of 45 ° to the horizontal plane, with the number of blades two or more, each subsequent blade located above the previous one is made of a larger diameter, the minimum length of the pile depends on the length of its screw part and layer freezing / thawing and is selected as a multiple of 0.5 meters, the key and significant parameters for the design bearing capacity of the pile F _{d, du} (t) are the length of the pile, the number of blades, the diameter of the trunk, the diameter of the blades, the extension of the blades so that the bearing capacity of the screw piles with a blade diameter d _n and a length L in permafrost soils, operating under compressive or pulling load, is determined in the following expression

, where F _{d, du} - bearing capacity of the pile (t), γ _s - coefficient of working conditions of the pile, equal to 0.9; γ _t - temperature coefficient equal to 0.8; R _i is the calculated resistance of frozen soil under the blade corresponding to the i-th layer of the soil base in which the i-th blade is located, t / m ² , R _{aƒ, i} is the calculated resistance of frozen soil to shear along the freezing surface of the pile material, corresponding to i- mu layer of the soil base, excluding the screw part, t / m ² , A _i - projection area of the i-th blade, m ² , A _{aƒ, i} - shear surface area according to the material of the pile body, corresponding to the i-th layer of the soil base, m ² , and the projection of the working area of the blade is determined by the formula

- the first blade in compression;

- the first blade when pulling and the remaining blades during compression and pulling, where D _hi is the diameter of the pile blade, m, d is the diameter of the pile shaft, m, t _w is the wall thickness of the pile, m, and the surface area of the shear along the ground is determined by the formula

, Where

pile shaft length, counting from the upper blade, m, D _hi - diameter of the upper pile blade, m 10. A pile according to claim 9, characterized in that the distance between the turns of the blades (dies) with blade diameters from 89 mm to 426 mm is determined in the range from 75 mm to 150 mm, and with the diameter D of the pile shaft in the range from 89 mm to 426 mm blade size is selected in the range from 120 mm to 690 mm, respectively.