Pile foundations for supporting power transmission towers

Abstract

Pile foundations for power transmission towers or the like for installation in different types of soil prone to frost heaving include a casing pipe and a dipped pile, comprising a shaft and a toe bulb, secured at the bottom of the shaft. The pile comprises rigid elements that are mounted on the shaft in the direction of horizontal forces acting on the pile against the anticipated horizontal loads. The rigid elements transfer horizontal forces from the pile to the casing pipe.

Claims

1. A pile foundation for supporting horizontal and vertical loads in substrates susceptible to frost heaving, the pile foundation comprising: a casing pipe; an immersed pile comprising a shaft and a toe bulb secured at the bottom of the shaft, positioned in the casing pipe; and rigid elements each comprising a generally flat plate directly mounted on the shaft transverse to horizontal forces from transmission lines acting on the pile and configured for transferring the horizontal forces from the pile to the casing pipe, the rigid elements arranged in pairs wherein the rigid elements are fixed on opposite sides of the shaft from one another and in a common plane transverse to the horizontal forces from the transmission lines.

2. The pile foundation of claim 1, wherein each of the rigid elements is disposed on the shaft and spaced apart by not less than the length of each of the rigid elements.

3. The pile foundation of claim 1, further comprising a cutoff screen mounted on the shaft from an upper part of the shaft to a level of seasonal freezing and thawing of soils.

4. The pile foundation of claim 3, wherein the cutoff screen comprises a plastic film or sheet.

5. The pile foundation of claim 3, wherein the cutoff screen comprises a galvanized metal sheet.

6. The pile foundation of claim 3, wherein the cutoff screen is fixed to the shaft using clamps.

7. The pile foundation of claim 1, wherein each of the rigid elements has a shape selected from square, triangular, and circular.

8. The pile foundation of claim 1, wherein the pile shaft is made of one of concrete, steel, or reinforced concrete.

9. The pile foundation of claim 1, wherein the pile toe bulb has a shape selected from tapered, circular, and flat.

10. The pile foundation of claim 1, wherein the toe bulb is secured by welding to the shaft.

11. The pile foundation of claim 1, wherein the toe bulb is secured by being molded as a single monolithic structure with the shaft.

12. The pile foundation of claim 1, wherein the casing is buried to a depth greater than a level of seasonal freezing and thawing of soils.

13. The pile foundation of claim 1, wherein a space between the casing and the shaft is filled with an inert non-heaving material.

14. The pile foundation of claim 13, wherein each of the rigid elements comprises a steel material.

15. The pile foundation of claim 13, wherein each of the rigid elements is in the range of 1-50 cm long, 1-20 cm wide, and 0.1-5 cm thick.

16. The pile foundation of claim 13, wherein each of the rigid elements is welded to the shaft.

17. The pile foundation of claim 13, wherein the shaft comprises a steel material.

18. The pile foundation of claim 1, wherein a space between the casing and the shaft is filled with one of concrete and mortar.

19. The pile foundation of claim 18, wherein the space between the casing pipe and the shaft is filled with one of an M100-M350 grade mortar and a B10-B40 grade concrete.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

(2) FIG. 1 is a schematic diagram illustrating a foundation pile with the casing pipe and rigid elements.

DETAILED DESCRIPTION

(3) Various aspects are now described with reference to FIG. 1, wherein the following components are illustrated: 1pile, 2pile shaft, 3pile toe bulb, 4casing pipe, 5filler, 6cutoff screen, 7rigid elements. Pile 1 comprises a shaft 2 and toe bulb 3. The pile shaft 1 may be made of concrete of grade B10-B40, of metal roll with 17G1S, 17G1S-U, St2kp, St2ps, St2sp, St3kp, St3ps, St3sp, St3ps3, St3sp3, St3ps4, St3sp40, or 9G2S steel grade, K34-K60 strength class, or reinforced concrete. The pile shaft 2 may have a length of L.sub.1, for example, in a range of 6-20 m, and a cylindrical shape with a diameter d.sub.1, for example, in a range of 15-150 cm. In an alternative, the pile shaft 2 may be rectangular in cross section with sides of dimension, for example, in a range of 10-100 cm by 10-100 cm. The pile shaft 2 serves to accommodate vertical, horizontal and other loads. The bottom of the pile shaft 2 may be attached with a pile toe bulb 3, which may be tapered, rounded or flat in shape and mounted to the shaft 2 by welding or molded as a single monolithic structure, in the case of configuration of concrete and reinforced concrete piles.

(4) The top of the shaft 2, which is 1 m to m long, may be attached with a cutoff screen 6 and rigid elements 7. The cutoff screen 6 may be made of plastic sheet or metal galvanized sheet. The cutoff screen 6 is installed close to the shaft 2 and fixed to it using clamps before or during driving the pile 1. The cutoff screen 6 is used to separate the pile 1 from the filling material in order to increase the reliability against the impact of frost heaving of the soil on the pile 1.

(5) Rigid elements 7 of the shaft 2 may be made of metal plates with 09G2S, 10G2, 15GS, 16GS, 17GS steel grade, for example, in a range of 1-50 cm long, 1-20 cm wide, and 0.1-5 cm thick. Rigid elements 7 may comprise a generally flat plate having a shape of square, triangular, circular or other non-arbitrary geometric shape. Rigid elements 7 are installed transverse to the anticipated horizontal forces acting on the pile 1, for example, horizontal forces from transmission lines. As shown in FIG. 1, the rigid elements may be attached in pairs on opposite sides of the shaft 2. The rigid elements 7 may be attached to the shaft 2 by welding vertically spaced apart by not less than the length of the rigid elements. Rigid elements 7 serve to transfer horizontal forces of the pile on the casing pipe 4.

(6) The pile shaft 2 is mounted into the casing pipe 4. The casing pipe 4 may be made of pipe metal-roll with 17G1S, 17G1S-U, St2kp, St2ps, St2sp, St3kp, St3ps, St3sp, St3ps3, St3sp3, St3ps4, St3sp40, 9G2S steel grade, K34-K60 strength class, with L.sub.2 length, for example, in a range of 1-10 m, with a diameter d.sub.2, for example, in a range of 20-200 cm. The casing pipe 4 serves to accommodate horizontal loads from the pile 1 and transfer them to the surrounding soil with a larger work area. The filler 5 of the space between the pile 1 and the casing pipe 4 is cement and sand mortar of M100-M350 grade, or B10-B40 grade concrete, or loose inert non-frost heaving material.

(7) The pile foundation may be installed as follows: A pilot hole for the pile may first be drilled, then the casing pipe 4 may be immersed into the soil by driving in around the pilot hole. Sinking of the casing pipe may be followed by drilling out the soil inside the casing pipe to a depth of immersion of the casing pipe. After drilling out the soil, the pile 1 may be driven in to design marks, for example, to a depth as shown in FIG. 1. Then the cavities between the pile 1 and the casing pipe 4 may filled with the filler 5, for example, with soil, or cement and sand (e.g., mortar or concrete). When using rigid elements 7 to transfer forces from the pile 1 to the casing pipe 4, before driving the pipe, rigid elements 7 may be mounted on the pile 1 followed by driving the pile 1 and filling the cavity between the pile 1 and the casing pipe 4.

(8) When mounting driven piles, drilling of the pile pilot hole is followed by the immersion of the casing pipe in the soil by driving it in, with the subsequent drilling out the soil inside the casing pipe to a depth of immersion of the casing pipe. After drilling out the soil, the pile is driven in the pilot hole up to design marks, and the cavities between the pile and the casing pipe are filled with soil or with cement and sand mortar (concrete). When using rigid elements to transfer forces from the pile to the casing pipe, before driving the pipe, rigid elements are mounted on the pile followed by the pile driving and filling the cavities between the pile and the casing pipe.