A conical-column type iron tower foundation in plateau permafrost area

Abstract

The present invention relates to a conical-column type iron tower foundation for plateau permafrost regions, which includes a main column and a bottom plate. The main column is conical, its bottom end is connected to the bottom plate, and its top end is provided with anchor bolts. The bottom plate is inverted conical, its conical surface faces downwards and is connected to the ground, and its horizontal plane faces upwards and is connected to the main column. The present invention is used for the iron tower foundation in plateau permafrost regions. The conical main column and the inverted conical bottom plate form a stable framework through steel bars and are cast integrally with concrete, which can rely on the advantages of the conical column shape of itself to completely or partially eliminate the tangential frost heaving force of the permafrost on the foundation. At the same time, the inverted conical structure of the bottom plate can also partially or completely eliminate the tangential frost heaving force of the permafrost on the bottom plate, thereby firmly supporting the iron tower; the use of a conical steel pipe with a smooth surface has a low friction coefficient, effectively reducing the problem of the foundation being uplifted and damaged caused by the frost heaving of the permafrost, avoiding the disadvantages that the straight-column foundation or the inclined-column foundation is vulnerable to frost heaving damage of the permafrost, and ensuring the safety and reliability of the line foundation in the permafrost area.

Description

Technical Field

[0001] The present invention relates to the field of building pile foundations, and particularly to a conical column type iron tower foundation for plateau permafrost regions. Background Art

[0002] The permafrost in Qinghai Province is the main body of permafrost at medium and low latitudes and high altitudes on the earth, and the altitude is the dominant factor controlling the development of permafrost. With the continuous development of the west-to-east power transmission and the regional power grid, it is inevitable for the power transmission lines to enter the permafrost regions in Qinghai. Further research and optimization of the design structure of the transmission line tower foundations in permafrost regions contribute to the stable operation of the power grid.

[0003] When the soil freezes, there are ice segregation aggregates with different thicknesses growing on its vertical and cross sections, which causes the soil particles to be isolated from each other, resulting in different degrees of displacement and causing the volume of the soil to expand. When the non-uniform expansion of the frozen soil layer is restricted by the foundation, different frost heaving forces will be generated on the foundation based on different restraint conditions. The overhead transmission lines in permafrost regions are often affected by the frost heaving and thaw settlement of the foundation soil to varying degrees, resulting in the instability of the tower foundation.

[0004] According to mechanical analysis, please refer to the appendix Figure 1 , the frost heaving forces received by the foundation are divided into the normal tension of horizontal frost heaving, the normal tension of vertical frost heaving and the tangential frost heaving force. Among them: the normal tension of vertical frost heaving refers to the upward reaction force generated by the magnetic layer foundation soil under the bottom surface of the foundation due to the obstruction of frost heaving, which will cause the foundation to be uplifted; the normal tension of horizontal frost heaving refers to the frost heaving pressure acting vertically on the surface of the foundation column, which is symmetric and has little impact on the foundation; the tangential frost heaving force is the freezing force generated when the permafrost foundation soil freezes together with the foundation surface, and due to the upward movement of the soil, a resistance parallel to the side surface of the foundation is generated, which will also cause the foundation to be uplifted, and it is related to the frost heaving property and freezing strength of the soil and the roughness of the foundation surface. Therefore, the horizontal normal frost heaving forces of the straight column foundation can cancel each other out, while the tangential frost heaving force and the basal normal frost heaving force will cause an uplift effect on the foundation, easily causing the uplift instability failure of the foundation.

[0005] Optimizing the design of the iron tower foundation is the common direction of scientific and technological workers in recent years. The conical column foundation described in the authorized announcement number CN20267,2174 U and the application publication number CN 110,XXX,XXX A has solved the problem of the stability of the iron tower foundation in permafrost regions to a certain extent. Please refer to the appendix Figure 2, the basic effective frost heaving force is generated by the unfrozen frost heaving soil. The tangential tension of frozen soil is related to the cracking of frozen soil near the ground surface, and the cracking of frozen soil is affected by the type, water content, and temperature of the soil near the ground surface. According to the different directions of the tension action, it can be known that the tangential frozen soil tension can be reduced by tilting the foundation surface. When the tilt angle of the foundation surface reaches the critical value, the tensile component acting on the foundation surface will be greater than the freezing tensile strength between the frozen soil and the foundation, and the frozen soil layer will be separated from the foundation surface and cracking will occur. At this time, the frost heaving activity in the cracking area cannot act on the foundation, that is, the tangential frost heaving force in the cracking area is zero, reducing the total frost heaving force acting on the foundation. Through practice, in the "Technical Specification for the Design of Foundations of Overhead Transmission Lines in Frozen Soil Areas DLT 5501-2015", it is stipulated in B.3.2-3 that it is better to take the minimum value of the taper of the main column of the foundation as 9 degrees. Then, the normal frost heaving force of the column part and the component force of the tangential frost heaving force in the vertical direction can cancel each other out, which can significantly reduce the influence of the tangential frost heaving force on the foundation. Therefore, it has been widely used in permafrost areas.

[0006] However, relying on the existing design and the problems encountered in on-site construction, there are still the following defects:

[0007] 1. The larger the taper of the main column of the foundation, the smaller the uplift thrust of the tangential frost heaving force on the foundation, but the volume of the foundation cone increases. By adjusting the buried depth, since the increment of the column area is greater than the increment of the column height, it will cause an increase in the consumption of concrete.

[0008] 2. The smaller the taper of the main column of the foundation, the greater the uplift thrust of the tangential frost heaving force on the foundation. By increasing the buried depth of the foundation, the tangential frost heaving area also increases, and the height of the foundation column is too large, which will cause an increase in the excavation depth of the foundation pit.

[0009] 3. The tangential frost heaving force is related to the foundation soil quality and frost heaving category. The tangential frost heaving forces of frozen soils with different soil qualities and categories are different. The tangential frost heaving force is related to the roughness of the foundation surface, and the roughness of the foundation surface has a greater impact on the foundation's resistance to frost heaving force. Summary of the Invention

[0010] In view of the technical defects existing in the existing foundation column design and on-site construction, the present invention provides a tapered column type iron tower foundation in alpine permafrost areas, aiming to improve the stability of the iron tower in alpine permafrost areas.

[0011] A tapered column type iron tower foundation in alpine permafrost areas includes a main column and a bottom plate. The main column is conical, its bottom end is connected to the bottom plate, and its top end is provided with anchor bolts 1. The bottom plate is inverted conical, its conical surface faces down and is connected to the ground, and its horizontal plane faces up and is connected to the main column.

[0012] Further, the bottom plate includes bottom plate lower reinforcing bars 7-12, bottom plate upper reinforcing bars 13, erection reinforcing bars 14 and concrete. The bottom plate lower reinforcing bars 7-12 are connected to the bottom plate upper reinforcing bars 13 through a number of erection reinforcing bars 14 to form a bottom plate skeleton, and concrete is poured to form the bottom plate.

[0013] Further, the main column includes main column main reinforcing bars 4, main column stirrups 5-6 and tapered steel pipes 15. The main column main reinforcing bars 4 and the main column stirrups 5-6 are connected to form a main column skeleton, and tapered steel pipes 15 are fixed on the outside thereof. The main column main reinforcing bars 4 are connected to the bottom plate skeleton, and concrete is poured between the main column skeleton and the tapered steel pipes 15 to form the main column.

[0014] Further, anchor bolts 1 are embedded in the main column. The anchor bolts 1 are fixed into a group of anchor bolts 1 with a specified planar dimension through anchor bolt stirrups 2-3 for connecting with the iron tower. The group of anchor bolts 1 is sleeved with anchor bolt protective caps 16 to protect them from being damaged.

[0015] Further, the column is conical, and the angle between its conical surface and the vertical direction is 9°; the bottom plate is inverted conical, and the angle between its conical surface and the vertical direction is 81°; the conical surface of the tapered steel pipe 15 has an angle of 9° with the vertical direction, and its surface is polished and anti-corrosion treated.

[0016] Further, the erection reinforcing bars 14 are of triangular prism type.

[0017] Further, the iron tower is fixed by four conical column type iron tower foundations in alpine permafrost regions.

[0018] Further, the concrete is C25, and the anchor bolt protective caps 16 are formed by C15 concrete.

[0019] Further, the steel type of the anchor bolts 1 is one of Q235, No. 35 steel or 42CrMo. The anchor bolt stirrups 2-3, the main column stirrups 5-6 and the erection reinforcing bars 14 are made of HRB300 steel, and the main column main reinforcing bars 4, the bottom plate lower reinforcing bars 7-12 and the bottom plate upper reinforcing bars 13 are made of HRB400 steel.

[0020] Further, the height of the iron tower is 18m, the distance A between the foundations is 3900mm, B is 3900mm, and L is 5515.4mm.

[0021] The implementation of the present invention has the following beneficial effects: The conical main column and the inverted conical bottom plate form a stable skeleton through steel bars and are integrated by concrete pouring, firmly and reliably supporting the iron tower; The structure of the concrete foundation column and the inverted conical bottom plate foundation formed by the conical steel pipe 15 can rely on the advantages of the conical column shape of itself to completely or partially eliminate the tangential frost heaving force of the frozen soil on the foundation. At the same time, the inverted conical structure of the bottom plate can also partially or completely eliminate the tangential frost heaving force of the frozen soil on the bottom plate. Moreover, the conical steel pipe 15 with a smooth surface has a low friction coefficient, greatly reducing the problem of the foundation being uplifted and damaged due to the frost heaving of the frozen soil, avoiding the disadvantages that the straight column foundation or the inclined column foundation is vulnerable to the frost heaving damage of the frozen soil, and ensuring the safety and reliability of the line foundation in the frozen soil area. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 : Force analysis diagram of the columnar foundation;

[0024] Figure 2 : Force analysis diagram of the conical columnar foundation;

[0025] Figure 3 : Schematic half-sectional view of the foundation elevation structure of the present invention

[0026] Figure 4 : Top view of the column part of the present invention;

[0027] Figure 5 : Top view of the partial section of the foundation of the present invention;

[0028] Figure 6 : Schematic road in the line direction of the present invention;

[0029] Figure 7 : Schematic diagram of the erection steel bar structure of the present invention;

[0030] In the figure: 1, anchor bolt; 2-3, anchor bolt stirrup; 4, main column main reinforcement; 5-6, main column stirrup; 7-12, bottom plate lower reinforcement; 13, bottom plate upper reinforcement; 14, erection steel bar; 15, conical steel pipe; 16, anchor bolt protective cap. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0032] In one embodiment of the present invention, please refer to the attached Figure 3-7 as shown:

[0033] A conical columnar iron tower foundation in alpine permafrost regions includes a main column and a bottom plate. The main column is conical, its bottom end is connected to the bottom plate, and its top end is provided with anchor bolts 1. The bottom plate is inverted conical, its conical surface faces down and is connected to the ground, and its horizontal plane faces up and is connected to the main column.

[0034] In the above structure, the conical main column can completely or partially eliminate the tangential frost heaving force of the permafrost on the foundation by relying on the advantages of its conical column shape. The inverted conical bottom plate can partially or completely eliminate the tangential frost heaving force of the permafrost on the bottom plate, thereby effectively reducing the defect that the foundation is uplifted due to frost heaving of the permafrost and causing foundation damage.

[0035] As one specific embodiment of the present invention:

[0036] The bottom plate includes bottom plate lower reinforcement bars 7 - 12, bottom plate upper reinforcement bars 13, erection reinforcement bars 14 and concrete. The bottom plate lower reinforcement bars 7 - 12 are connected to the bottom plate upper reinforcement bars 13 through a plurality of erection reinforcement bars 14 to form a bottom plate skeleton, and concrete is poured to form the bottom plate.

[0037] The main column includes main column main reinforcement bars 4, main column stirrups 5 - 6 and a conical steel pipe 15. The main column main reinforcement bars 4 and the main column stirrups 5 - 6 are connected to form a main column skeleton, and a conical steel pipe 15 is fixed on the outside thereof. The main column main reinforcement bars 4 are connected to the bottom plate skeleton, and concrete is poured between the main column skeleton and the conical steel pipe 15 to form the main column.

[0038] Anchor bolts 1 are embedded in the main column. The anchor bolts 1 are fixed into a group of anchor bolts 1 with a specified planar dimension through anchor bolt stirrups 2 - 3 for connecting with the iron tower. This group of anchor bolts 1 is sleeved with an anchor bolt protective cap 16 to protect it from damage.

[0039] The concrete conical main column formed by the conical steel pipe 15 and the inverted conical bottom plate form a stable skeleton through steel bars and are formed into one body by concrete pouring, firmly and reliably supporting the iron tower, improving the stability performance of the iron tower; by installing the anchor bolt protective cap 16 on the group of anchor bolts 1, the bolt fittings are effectively protected from being damaged by external forces and prevented from being exposed to form corrosion.

[0040] As one preferred embodiment of the present invention:

[0041] The upright column is conical, and the angle between its conical surface and the vertical direction is 9°; the bottom plate is inverted conical, and the angle between its conical surface and the vertical direction is 81°; the conical surface of the conical steel pipe 15 has an angle of 9° with the vertical direction, and its surface is polished and anti-corrosion treated.

[0042] Since the taper of the foundation main column is 9°, the normal frost heaving force and the tangential frost heaving force of the column part can cancel each other out in the vertical direction. Since the taper of the inverted conical bottom plate is 81°, the normal frost heaving force and the tangential frost heaving force of the bottom plate part are reduced to a certain extent in the vertical direction, which can significantly reduce the influence of the tangential frost heaving force on the foundation; moreover, the conical steel pipe 15 with polished and anti-corrosion treatment has a low friction coefficient and good anti-corrosion performance, effectively reducing the roughness of the foundation surface, further reducing the problem of uplift failure of the foundation caused by the tangential frost heaving force, avoiding the disadvantages of the straight column foundation or the inclined column foundation being vulnerable to frost heaving damage in frozen soil areas, and ensuring the safety and reliability of the line foundation in frozen soil areas.

[0043] As one of the preferred embodiments of the present invention:

[0044] The erection steel bars 14 are triangular prism-shaped, and their symmetrical structure ensures the stable structure of the bottom reinforcement 7-12 of the bottom plate and the top reinforcement 13 of the bottom plate, thereby enhancing the strength of the inverted conical bottom plate and enabling the foundation main column to have a stable foundation support surface.

[0045] As one of the preferred embodiments of the present invention:

[0046] The iron tower is fixed by four conical column-shaped iron tower foundations in the high-altitude frozen soil area, so that the weight of the iron tower is evenly distributed to the four foundations, which not only reduces the volume of a single foundation but also reduces the construction difficulty.

[0047] As one of the preferred embodiments of the present invention:

[0048] The concrete used is C25, and the anchor bolt cap 16 is formed by C15 concrete. The C25 concrete improves the strength of the foundation. When using the anchor bolt cap 16, the C15 concrete can be quickly removed, and both have relatively low costs.

[0049] As one of the preferred embodiments of the present invention:

[0050] The steel material model of the anchor bolt 1 is one of Q235, No. 35 steel or 42CrMo. The anchor bolt stirrups 2-3, the main column stirrups 5-6 and the erection steel bars 14 are made of HRB300 steel, and the main column main reinforcement 4, the bottom reinforcement 7-12 of the bottom plate and the top reinforcement 13 of the bottom plate are made of HRB400 steel; all have relatively low costs.

[0051] As one of the preferred embodiments of the present invention:

[0052] The height of the iron tower is 18m, the distance A between the foundations is 3900mm, B is 3900mm, and L is 5515.4mm. It has a good optimized structure and effectively improves the stability performance of the iron tower.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A conical-column type iron tower foundation in alpine permafrost regions, comprising a main column and a bottom plate, characterized in that, The main column is conical, its bottom end is connected to the bottom plate, and its top end is provided with anchor bolts (1). The bottom plate is inverted conical, its conical surface faces down and is connected to the ground, and its horizontal plane faces up and is connected to the main column. The main column includes main column longitudinal bars (4), main column stirrups (5-6), and a conical steel pipe (15). The main column longitudinal bars (4) and the main column stirrups (5-6) are connected to form a main column skeleton, and the conical steel pipe (15) is fixed on the outside. The main column longitudinal bars (4) are connected to the bottom plate skeleton, and concrete is poured between the main column skeleton and the conical steel pipe (15) to form the main column. The angle between the conical surface of the main column and the vertical direction is 9°. The angle between the conical surface of the bottom plate and the vertical direction is 81°. The angle between the conical surface of the conical steel pipe (15) and the vertical direction is 9°, and its surface is polished and anti-corrosion treated.

2. The conical-column type iron tower foundation in alpine permafrost regions according to claim 1, wherein, The bottom plate includes bottom plate bottom bars (7-12), bottom plate top bars (13), erection bars (14), and concrete. The bottom plate bottom bars (7-12) are connected to the bottom plate top bars (13) through a number of erection bars (14) to form a bottom plate skeleton, and concrete is poured to form the bottom plate.

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