Structure for improving bearing capacity of manual hole digging pile foundation of power transmission line in mountainous area

Abstract

The utility model discloses a structure for improving the bearing capacity of a manual hole digging pile foundation of a power transmission line in a mountainous area. The structure comprises a pile foundation, concrete is poured on the side wall of the pile foundation to form a protection wall, a platform of a rectangular structure is arranged on the upper portion of the pile foundation and located at the position one meter below the original ground of the pile foundation, the height of the platform is larger than one time of the diameter of the pile foundation, and the pile foundation is surrounded in the center. The bearing capacity of the manual hole digging pile foundation is improved by adding a platform structure, so that the project amount scrap is reduced, the concrete protection wall is not damaged to the maximum extent, and the construction operation difficulty is reduced.

Description

Technical Field

[0001] The utility model relates to a structure for improving the bearing capacity of a manual bored pile foundation of a power transmission line in a mountainous area, and belongs to the field of overhead power transmission line engineering. Background Art

[0002] A large number of transmission lines are laid out in mountainous areas. As transmission lines are linear projects, the geotechnical survey stage involves a large number of survey tower sites, inconvenient transportation, and difficulty in bringing large-scale exploration equipment to the site. As a result, in the actual foundation construction process, the actual engineering geological conditions often do not match the survey and design data, especially the insufficient bearing capacity of the pile foundation. As a result, the original design foundation plan needs to be verified and demonstrated, and design changes need to be issued.

[0003] Transmission lines in mountainous areas mostly use bored pile foundations. During the excavation of the pile foundation, reinforced concrete retaining walls are cast simultaneously, and the steel cage is laid and tied simultaneously. In order to reduce the amount of scrapped projects, minimize the damage to the concrete retaining walls, do not change the original designed pile length and pile diameter, and reduce the difficulty of construction operations, a structure that can improve the bearing capacity of bored pile foundations for transmission lines in mountainous areas is proposed. Utility Model Content

[0004] The utility model provides a structure for improving the bearing capacity of a manual bored pile foundation of a power transmission line in a mountainous area, so as to solve the above-mentioned problem.

[0005] The technical scheme of the utility model is a structure for improving the bearing capacity of artificial bored pile foundation of power transmission line in mountainous area, comprising a pile foundation, a side wall of the pile foundation is poured with concrete to form a protective wall, a platform is arranged on the upper part of the pile foundation, and the platform surrounds the pile foundation in the center.

[0006] Preferably, the platform is rectangular, the top surface of the platform is located 1 meter below the original ground surface of the pile foundation, and the height of the platform is greater than 1 times the diameter of the pile foundation.

[0007] Preferably, a plurality of vertical bars are arranged in the platform, and the top and bottom ends of the plurality of vertical bars are connected with upper steel bars and lower steel bars respectively, and the upper steel bars and lower steel bars are arranged through the retaining wall and the pile foundation.

[0008] Preferably, four groups of reinforcing ribs are cross-arranged outside the protective wall in the platform, each group of reinforcing ribs is at right angles to each other, and the end of each group of reinforcing ribs extends to the edge of the platform and is bent downward and anchored.

[0009] Preferably, each group of reinforcing ribs uses at least three steel bars arranged in parallel with a spacing of 50 mm and a diameter the same as the upper and lower steel bars of the platform, and the innermost reinforcing rib is tangent to the retaining wall.

[0010] Compared with the prior art, the beneficial effect of the utility model is that, based on the excavated pile foundation, the actual stratum distribution, parameters and original design conditions of the bored pile foundation are verified. For pile foundations that do not meet the bearing capacity requirements, the bearing capacity of the bored pile foundation is improved by adding a platform structure without changing the original design pile length and pile diameter, thereby reducing the amount of scrapped projects, minimizing damage to the concrete retaining wall and reducing the difficulty of construction operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of the utility model;

[0012] Figure 2 It is a top view of the utility model. DETAILED DESCRIPTION

[0013] The present invention will be further explained below in conjunction with the accompanying drawings to facilitate better understanding by those skilled in the art.

[0014] Example 1

[0015] like Figure 1-2 As shown, a structure for improving the bearing capacity of bored pile foundations of power transmission lines in mountainous areas comprises a pile foundation 1, a bottom expansion 8 is provided at the bottom of the pile foundation, concrete is poured on the side walls of the pile foundation 1 to form a retaining wall 2, a rectangular platform 3 is provided on the upper part of the pile foundation 1, 1 meter below the original ground surface of the pile foundation 1, the platform 3 is poured with concrete, the pile foundation 1 is surrounded in the center, and the height of the platform 3 is greater than 1 times the diameter of the pile foundation 1, the bearing capacity of the bored pile foundation is improved by adding the platform 3 structure, thereby reducing the amount of scrapped engineering, minimizing the damage to the concrete retaining wall and reducing the difficulty of construction operations.

[0016] Furthermore, a plurality of vertical bars 4 are arranged in the platform 3, and the top and bottom ends of the plurality of vertical bars 4 are connected by upper steel bars 5 and lower steel bars 6 respectively to form a stable steel cage, and the upper steel bars 5 and the lower steel bars 6 are arranged to penetrate the retaining wall 2 and the pile foundation 1 to ensure that the platform 3 structure and the bored pile foundation are subjected to stress together.

[0017] Four groups of reinforcing ribs 7 are cross-arranged on the outside of the retaining wall 2 in the platform 3, and each group of reinforcing ribs 7 is at right angles to each other. The end of each group of reinforcing ribs 7 extends to the edge of the platform 3, bends downward and is anchored. Each group of reinforcing ribs 7 uses at least three steel bars arranged in parallel with a spacing of 50 mm. The diameter is the same as the upper 5 and lower steel bars 6 of the platform. The innermost reinforcing rib 7 is tangent to the retaining wall to ensure the connection strength between the platform 3 and the bored pile foundation.

[0018] Construction method:

[0019] Step 1: Verify the actual stratum distribution and parameters of the bored pile foundation based on the excavated pile foundation and the differences with the original design conditions.

[0020] Step 2: Review the upper and lower bearing capacities of the originally designed bored pile foundation according to the actual stratum distribution and parameters.

[0021] Pressure bearing capacity: N k ≤η p (μ∑ψ si q sik l i +ψ p q pk A p ) / K

[0022] Pull-out load capacity: T k ≤(∑λ i q sik μ i l i ) / K1+G p N k -Standard value of pressure load on bored pile foundation

[0023] η p -Adjustment coefficient of the bearing capacity of bored pile foundation

[0024] μ- perimeter of bored pile foundation

[0025] ψ si -Side drag size effect coefficient

[0026] ψ p -End resistance size effect coefficient

[0027] q sik - Standard value of the ultimate lateral resistance of the i-th layer of soil (rock), corresponding to the expanded bottom variable cross-section pile with a length of more than 2d without considering the pile lateral resistance

[0028] l i -Thickness of the i-th layer of soil (rock) within the length of the pile

[0029] q pk -Standard value of ultimate pile end resistance

[0030] A p - Cross-sectional area of ​​pile tip

[0031] K- safety factor of downward pressure bearing capacity

[0032] λ i - Pull-out coefficient of the i-th layer of soil on the pile side

[0033] K1-pull-out bearing capacity safety factor

[0034] G p - Deadweight of pile foundation

[0035] Step 3: If both equations in step 2 are true, the originally designed bored pile foundation meets the requirements of upper pull and lower pressure bearing capacity. If any equation in step 2 is not true, the bearing capacity of the bored pile foundation is improved by adding a platform structure.

[0036] Step 4: Add a rectangular reinforced concrete platform structure 1 meter below the original ground of the bored pile foundation. According to the characteristics of the bearing layer of the platform structure base, calculate the width (diameter) of the platform structure according to the following formula:

[0037] Pressure bearing capacity: N k +G k +G p ≤η p (μ∑ψ si q sik l i +ψ p q pk A p )+η C f ak A c / K

[0038] Pull-out load capacity: T k ≤(∑λ i q sik μ i l i ) / K1+G k +G p

[0039] G k - The deadweight of the platform structure and the deadweight of the upper covering soil

[0040] η C -Platform structure effect coefficient

[0041] f ak - Weighted average value of the bearing capacity characteristic value of each soil (rock) layer within the width of the platform structure (not more than 5m) by thickness

[0042] A c - Net area of ​​platform structure (deducting pile foundation area)

[0043] Step 5: After the width (diameter) of the platform structure is determined, the bending bearing capacity of the platform's positive section must be calculated in accordance with the requirements of the Code for Design of Concrete Structures (GB50010) to determine the platform height and reinforcement. At the same time, in order to meet the platform stiffness requirements and ensure the linear distribution of the platform foundation reaction force, the platform height must be greater than 1 times the pile diameter.

[0044] Step 6: To ensure that the platform structure and the bored pile foundation are subjected to stress together, holes need to be opened at the corresponding positions on the retaining wall, and the upper and lower steel bars of the platform need to be arranged through the holes in the concrete retaining wall. Three oblique reinforcement steel bars need to be arranged on the outside of the platform retaining wall, with a spacing of 50mm and the same diameter as the upper and lower steel bars of the platform to ensure the connection strength between the platform and the original structure.

[0045] The above-mentioned embodiments are only for describing the preferred implementation of the utility model, and are not intended to limit the scope of the utility model. Without departing from the design spirit and principle of the utility model, various modifications and improvements made by those skilled in the art to the technical solution of the utility model shall fall within the protection scope determined by the claims of the utility model.

Claims

1. A structure for improving the bearing capacity of artificial bored pile foundations of power transmission lines in mountainous areas, characterized in that: The invention comprises a pile foundation (1), the side wall of the pile foundation (1) is poured with concrete to form a protective wall (2), and a platform (3) is provided on the upper part of the pile foundation (1), and the platform (3) surrounds the pile foundation (1) in the center.

2. A structure for improving the bearing capacity of artificial bored pile foundations for power transmission lines in mountainous areas according to claim 1, characterized in that: The platform (3) is rectangular and is located 1 meter below the original ground surface of the pile foundation (1). The height of the platform (3) is greater than 1 times the diameter of the pile foundation (1).

3. A structure for improving the bearing capacity of artificial bored pile foundations for power transmission lines in mountainous areas according to claim 2, characterized in that: A plurality of vertical bars (4) are arranged in the platform (3), and the top and bottom ends of the plurality of vertical bars (4) are connected by upper steel bars (5) and lower steel bars (6) respectively, and the upper steel bars (5) and the lower steel bars (6) are arranged to penetrate the retaining wall (2) and the pile foundation (1) and are connected.

4. A structure for improving the bearing capacity of bored pile foundations for power transmission lines in mountainous areas according to claim 3, characterized in that: Four groups of reinforcing ribs (7) are cross-arranged inside the platform (3) and outside the protective wall (2), with each group of reinforcing ribs (7) forming right angles with each other, and the ends of each group of reinforcing ribs (7) extend to the edge of the platform (3) and are bent downwards and anchored.

5. A structure for improving the bearing capacity of artificial bored pile foundations for power transmission lines in mountainous areas according to claim 4, characterized in that: Each group of reinforcing ribs (7) is composed of at least three steel bars arranged in parallel, with a spacing of 50 mm and a diameter equal to that of the upper steel bars (5) and the lower steel bars (6) of the platform, and the innermost reinforcing rib (7) is tangent to the retaining wall (2).

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