In-situ transformation mixed tower foundation and construction method thereof

Abstract

The invention provides an in-situ transformation mixed tower foundation and a construction method thereof.The in-situ transformation mixed tower foundation comprises an original small mixed tower foundation and a newly-arranged foundation, the newly-arranged foundation is formed by pouring on the outer surface of the original small mixed tower foundation through a restrictive section expansion method, and a pre-stressed anchor cable stress steering device is arranged in the newly-arranged foundation; the device is used for conducting direction transfer on the pre-stressed anchor cable tensioning force. The new foundation is poured on the outer side of the original foundation, the new foundation and the old foundation are connected through embedded steel bars, the pre-stressed anchor cable stress steering device is arranged in the foundation, a cavity of the original foundation and an anchor cable hole channel in the original foundation are utilized, the tensioning force of the pre-stressed anchor cable can be transferred in the direction, and the original anchor cable pre-stressed hole channel is effectively applied.

Description

Technical Field

[0001] The invention relates to the technical field of wind power foundation reconstruction, and in particular to an in-situ reconstruction of a mixed tower foundation and a construction method thereof. Background Art

[0002] In the field of wind power construction, some small wind turbines use a mixed tower structure (that is, the wall of the wind turbine tower adopts a reinforced concrete structure), and its foundation is set as a mixed tower foundation. The difference between the mixed tower foundation and the conventional foundation is that a cavity is set in the middle of the foundation to facilitate maintenance personnel to enter the cavity to inspect and maintain the prestressed anchor cables of the mixed tower. With the demand for upgrading and reconstruction of small units, a batch of small unit mixed towers will be upgraded to improve the utilization hours and power generation of wind power and improve the economic benefits of wind farms. Considering these small units that have previously adopted the mixed tower structure, because of the experience of using the mixed tower structure and the application advantages of the mixed tower structure in large units, it is highly likely that the mixed tower structure will still be used when the wind farm is upgraded.

[0003] According to the current existing technology, the original small unit's mixed tower structure and its lower mixed tower foundation will be completely demolished and a new mixed tower foundation will be built. The existing construction measures have the disadvantages of poor environmental protection, poor resource utilization, high engineering construction cost, and long construction period due to the need to demolish the original infrastructure. Therefore, it is necessary to develop an in-situ transformation of the mixed tower foundation and construction method to solve the problems of the misalignment of the new mixed tower external prestressed anchor cable and the original foundation prestressed anchor cable channel involved in the in-situ transformation of the foundation during the upgrading and transformation process, and the insufficient bearing capacity of the original foundation, which has a good application prospect. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ modified concrete tower foundation and a construction method thereof, so as to effectively solve the problems of misalignment between the external prestressed anchor cables of the new concrete tower and the prestressed anchor cable holes of the original foundation and insufficient bearing capacity of the original foundation.

[0005] According to the purpose of the present invention, the present invention provides an in-situ modified concrete tower foundation, comprising an original small concrete tower foundation and a newly established foundation, wherein the newly established foundation is formed by casting on the outer surface of the original small concrete tower foundation by a restricted expansion section method, and a prestressed anchor cable force steering device is arranged in the newly established foundation for transferring the direction of the prestressed anchor cable tensioning force.

[0006] Furthermore, the original small concrete tower foundation is integrally formed of a bottom cylinder, a middle frustum and a top hollow cylinder; the newly-built foundation includes a new middle frustum and a new top hollow cylinder, and the connection between the new and old foundations is strengthened by embedded reinforcement and an interface agent.

[0007] Furthermore, the top hollow cylinder of the original small concrete tower foundation is removed within a height range and the original steel bars are retained, and are reused in the new top hollow cylinder of the newly established foundation.

[0008] Furthermore, the outer surface of the original small concrete tower foundation is reinforced with 12mm diameter steel bars with a longitudinal and transverse interval of 300mm, and the embedded depth is not less than 250mm.

[0009] Furthermore, the joint surface between the original small concrete tower foundation and the newly-built foundation is roughened, and an interface agent is applied before pouring to enhance the connection strength.

[0010] Furthermore, the newly-established foundation is designed by a restrictive expansion section method, and its width is expanded outside the original small concrete tower foundation; the restrictive principle of the restrictive expansion section method is that the steel bars of the original small concrete tower foundation maintain the original configuration and are connected to the steel bars in the newly-established foundation.

[0011] Furthermore, the prestressed anchor cable force steering device includes an upper steel pipe, a middle steel pipe, a lower steel pipe and a steering wheel; the upper steel pipe is buried in the newly established foundation, the lower steel pipe is nested in the prestressed anchor cable channel of the original small concrete tower foundation, the middle steel pipe is welded to connect the upper steel pipe and the lower steel pipe, and the steering wheel includes a fixed shaft and a movable wheel, and the movable wheel rotates around the fixed shaft to realize the direction transfer of the tensioning force of the prestressed anchor cable.

[0012] Furthermore, the prestressed anchor cable force steering device also includes a sealing cover, which is used to prevent damage to the steering wheel during concrete pouring and provide protection against corrosion and environmental erosion; the sealing cover is made of high-strength composite material or corrosion-resistant metal.

[0013] Furthermore, the prestressed anchor cable holes of the original small concrete tower foundation are retained and reused; the prestressed anchor cables in the new concrete tower foundation pass through the original anchor cable holes through the steering device and achieve effective direction transfer.

[0014] According to another object of the present invention, the present invention provides a construction method for in-situ transformation of a concrete tower foundation, comprising the following steps:

[0015] S1: The original hollow cylinder at the top of the existing small concrete tower foundation is removed within the height range, and the original steel bars are retained for reuse in the new concrete tower foundation;

[0016] S2: The outer surface of the original small concrete tower foundation is treated with 12mm diameter steel bars at intervals of 300mm in the vertical and horizontal directions. The length of the steel bars in the new and old foundations is not less than 250mm. After the steel bars are planted on the surface of the original small concrete tower foundation, the surface is roughened and cleaned;

[0017] S3: A new foundation is set on the outer surface of the original small concrete tower foundation. The interface agent is applied to the joint surface between the new foundation and the original small concrete tower foundation before the new foundation is poured. The width of the new foundation expanded outward from the original small concrete tower foundation, the height of the new middle frustum and the new top hollow cylinder, and the steel bars inside the new foundation are determined by finite element calculation. The principle of determination is that the steel bars inside the original small concrete tower foundation remain unchanged.

[0018] S4: The force conversion of the prestressed anchor cable is carried out in the foundation. A prestressed anchor cable force steering device is arranged in the new foundation. The prestressed anchor cable force steering device transfers the direction of the tensioning force of the prestressed anchor cable through the movable wheel arranged inside, and the original prestressed hole of the anchor cable is effectively utilized.

[0019] The technical solution of the present invention is to cast a new foundation outside the original foundation, connect the new and old foundations with rebar, and set a prestressed anchor cable force steering device in the foundation, making use of the original foundation cavity and the anchor cable channel in the original foundation, so as to transfer the tensioning force of the prestressed anchor cable, and effectively utilize the original anchor cable prestressed channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a top view of the original small mixing tower foundation plane of an embodiment of the present invention;

[0022] Figure 2 This is a cross-sectional view of the original small mixing tower foundation of an embodiment of the present invention;

[0023] Figure 3 This is a top view of the foundation plane of the large mixing tower after the transformation according to the embodiment of the present invention;

[0024] Figure 4 This is a cross-sectional view of the foundation of the large mixing tower after transformation according to an embodiment of the present invention;

[0025] Figure 5 is a cross-sectional view of a steering device according to an embodiment of the present invention;

[0026] Figure 6 This is a top view of a steering device according to an embodiment of the present invention;

[0027] In the figure: 1, the original small concrete tower foundation; 101, the original bottom cylinder; 102, the original middle truncated cone; 103, the original top hollow cylinder;

[0028] 2. New foundation; 201. New frustum in the middle; 202. New hollow cylinder at the top;

[0029] 3. The wall of the original small concrete tower; 4. The foundation; 5. The wall of the new concrete tower; 6. The prestressed anchor cable of the new concrete tower; 7. The prestressed anchor cable of the original small concrete tower; 8. The original prestressed anchor cable hole;

[0030] 9. Prestressed anchor cable force steering device; 901. Upper steel pipe; 902. Middle steel pipe; 903. Lower steel pipe; 904. Steering wheel; 905. Sealing cover; 9041. Fixed shaft; 9042. Movable wheel. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Example 1

[0035] like Figure 1-Figure 6 As shown,

[0036] An in-situ modified concrete tower foundation comprises an original small concrete tower foundation 1 and a newly established foundation 2, wherein:

[0037] The original small mixing tower wall 3 is fixed on the original small mixing tower foundation 1. The original small mixing tower foundation 1 includes the original bottom cylinder 101, the original middle frustum body 102 and the original top hollow cylinder 103. The original bottom cylinder 101, the original middle frustum body 102 and the original top hollow cylinder 103 are integrally formed from bottom to top, and the original bottom cylinder 101 is fixed on the foundation 4.

[0038] The new concrete tower wall 5 is fixed on the newly built foundation 2 , which includes a new middle frustum 201 cast on the outside of the original middle frustum 102 and a new top hollow cylinder 202 cast at the position of the original top hollow cylinder 103 .

[0039] Specifically, when the new foundation 2 is being poured, the original top hollow cylinder 103 of the original small concrete tower foundation 1 is completely removed within the height H1, and the original steel bars are retained and poured together with the new top hollow cylinder 202 of the new foundation 2 for reuse.

[0040] Specifically, when the newly-established foundation 2 is poured, the outer surface of the original small concrete tower foundation 1 is treated with surface reinforcement with 12mm diameter steel bars at intervals of 300mm in the vertical and horizontal directions. The length of the steel bars in the new and old foundations is not less than 250mm. After the surface of the original small concrete tower foundation 1 is reinforced, it is roughened and cleaned.

[0041] Specifically, a new foundation 2 is set on the outer surface of the original small concrete tower foundation 1, and the interface agent is brushed on the bonding surface between the new foundation 2 and the original small concrete tower foundation 1 before the new foundation 2 is poured. The dimensions of the new foundation 2, the outer expansion width B of the original small concrete tower foundation 1, the new middle frustum H4, the height H3 of the new top hollow cylinder, and the steel bars in the new foundation 2 are determined through finite element calculation, and the determination principle is that the internal steel bars of the original small concrete tower foundation remain unchanged.

[0042] Specifically,

[0043] Because the diameter of the new concrete tower wall 5 is larger than that of the original small concrete tower wall 3, the new concrete tower wall 5 will be located outside the demolished original small concrete tower wall 3, and the width B2 of the new top hollow cylinder of the newly established foundation 2 will be larger than the width B1 of the original top hollow cylinder of the original small concrete tower foundation 1.

[0044] The new concrete tower body prestressed anchor cable 6 will also be located outside the original small concrete tower body prestressed anchor cable 7 that has been removed. The original prestressed anchor cable duct 8 and the new concrete tower body prestressed anchor cable 6 will not be on the same vertical line, and the new concrete tower body prestressed anchor cable 6 will have a folded angle when prestressing, which will be extremely unfavorable for the tensioning work of the prestressed anchor cable and easily cause damage to the new concrete tower body prestressed anchor cable 6 and data distortion.

[0045] The force conversion of the prestressed anchor cable is carried out in the foundation, and a prestressed anchor cable force steering device 9 is arranged in the newly established foundation 2. The prestressed anchor cable force steering device 9 can easily transfer the direction of the tensioning force of the prestressed anchor cable through the movable wheel 9042 arranged inside, and the original prestressed anchor cable channel 8 is effectively used.

[0046] Specifically, the prestressed anchor cable force steering device 9 includes five parts, namely an upper steel pipe 901, a middle steel pipe 902, a lower steel pipe 903, a steering wheel 904 and a sealing cover 905, wherein:

[0047] The steering wheel 904 includes a fixed shaft 9041 and a movable wheel 9042. The fixed shaft 9041 is fixedly welded to the bottom of the upper steel pipe 901 and the top of the lower steel pipe 903. The movable wheel 9042 is wrapped around the fixed shaft 9041 and can rotate and roll around the fixed shaft 9041 with extremely small friction.

[0048] The upper steel pipe 901 is arranged directly below the prestressed anchor cable 6 of the new concrete tower body and buried in the newly established foundation 2. The inner and outer lengths of the upper steel pipe 901 in the newly established foundation 2 are not less than 250 mm. The lower end of the lower steel pipe 903 is embedded in the original prestressed anchor cable channel 8 of the original small concrete tower foundation, and the upper end is arranged in the newly established foundation 2. The length of the lower steel pipe 903 in the new and old foundations is not less than 250 mm. The middle steel pipe 902 is welded to connect the upper steel pipe 901 and the lower steel pipe 3-2 to protect the new concrete tower body prestressed anchor cable 6 therein.

[0049] The construction method of in-situ transformation of a concrete tower foundation of the present invention comprises the following steps:

[0050] 1. The wind tower foundation of wind power equipment is generally divided into three parts, namely the bottom cylinder, the middle frustum and the top frustum. For the mixed tower foundation, the mixed tower wall is provided with prestressed anchor cables outside the body, and the prestressed anchor cables need to be tensioned and repaired and maintained. To meet this demand, the wind tower foundation is generally provided with a cavity inside to facilitate personnel to enter the foundation to tension and repair the prestressed anchor cables. This wind tower foundation with a cavity forms a special mixed tower foundation.

[0051] Because the new concrete tower wall 5 has a larger diameter than the original small concrete tower wall 3, the new concrete tower wall 5 will be located outside the dismantled original small concrete tower wall 3, and the width B2 of the hollow cylinder at the top of the new large unit concrete tower will be larger than the width B1 of the hollow cylinder at the top of the original small unit concrete tower, to facilitate the installation of the prestressed anchor cable force device 3.

[0052] The first step of the present invention is to completely dismantle the original top hollow cylinder of the existing small concrete tower foundation within the height H1 range, and retain the original steel bars in the new concrete tower foundation for reuse;

[0053] 2. Because the force of the original small concrete tower foundation is generally difficult to meet the new large concrete tower foundation, and the diameter of the large concrete tower foundation is generally larger than the original small concrete tower foundation diameter, in order to meet the force requirements of the new large concrete tower foundation, when the wind power small concrete tower is upgraded to a large concrete tower, it is necessary to use the extended section method to reuse the small concrete tower foundation. The wind tower foundation is subjected to wind load for a long time, and the fatigue effect is obvious. In order to solve the problem of combining the new and old foundations during the in-situ transformation of the wind tower foundation, it is necessary to carry out the surface treatment of the new and old foundations.

[0054] The second step of the present invention is to carry out surface reinforcement treatment of 12mm diameter steel bars at intervals of 300mm in the vertical and horizontal directions on the outer surface of the original small concrete tower foundation 1, and the length of the steel bars in the new and old foundations is not less than 250mm, and the surface of the original small concrete tower foundation is roughened and cleaned after the steel bars are planted;

[0055] 3. In order to solve the problem of insufficient force on the original foundation during the in-situ transformation of the new large concrete tower foundation and the reuse of the old foundation, it is necessary to use the extended section method or other methods to set up a new foundation on the surface of the old foundation.

[0056] The third step of the present invention is to set a new foundation 2 on the outer surface of the original small concrete tower foundation 1, and brush the interface agent in advance on the joint surface of the new foundation 2 and the original small concrete tower foundation 1 before pouring the new foundation 2. The dimensions of the new foundation 2, the outer expansion width B of the original small concrete tower foundation 1, the new middle frustum H4, the height H3 of the new top hollow cylinder, and the steel bars in the new foundation 2 are determined by finite element calculation, and the determination principle is that the steel bars inside the original small concrete tower foundation remain unchanged;

[0057] 4. Because the new concrete tower wall 5 has a larger diameter than the original small concrete tower wall 3, the new concrete tower wall 5 will be located outside the dismantled original small concrete tower wall 3, and the new concrete tower body prestressed anchor cable 6 will also be located outside the dismantled original small concrete tower body prestressed anchor cable 7. The original prestressed anchor cable duct 8 and the new concrete tower body prestressed anchor cable 6 will not be on the same vertical line, and the new concrete tower body prestressed anchor cable 6 will have a folded angle when prestressing, which will be extremely unfavorable for the tensioning work of the prestressed anchor cable and easily cause damage to the new concrete tower body prestressed anchor cable 6 and data distortion.

[0058] The fourth step of the present invention is to perform force conversion of the prestressed anchor cable in the foundation, and to set a prestressed anchor cable force steering device 9 in the newly established foundation 2. The prestressed anchor cable force steering device 9 can easily transfer the direction of the tensioning force of the prestressed anchor cable through the movable wheel 9042 arranged inside, and the original anchor cable prestressed channel 4 is effectively utilized.

[0059] Specifically, the prestressed anchor cable force steering device 9 includes five parts, namely an upper steel pipe 901, a middle steel pipe 902, a lower steel pipe 903, a steering wheel 904 and a sealing cover 905, wherein:

[0060] The steering wheel 904 includes a fixed shaft 9041 and a movable wheel 9042. The fixed shaft 9041 is fixedly welded to the bottom of the upper steel pipe 901 and the top of the lower steel pipe 903. The movable wheel 9042 is wrapped around the fixed shaft 9041 and can rotate and roll around the fixed shaft 9041 with extremely small friction.

[0061] The upper steel pipe 901 is arranged directly below the prestressed anchor cable 6 of the new concrete tower body and buried in the newly established foundation 2. The inner and outer lengths of the upper steel pipe 901 in the newly established foundation 2 are not less than 250 mm. The lower end of the lower steel pipe 903 is embedded in the original prestressed anchor cable channel 8 of the original small concrete tower foundation, and the upper end is arranged in the newly established foundation 2. The length of the lower steel pipe 903 in the new and old foundations is not less than 250 mm. The middle steel pipe 902 is welded to connect the upper steel pipe 901 and the lower steel pipe 3-2 to protect the new concrete tower body prestressed anchor cable 6 therein.

[0062] Through the above arrangement, the new foundation 2 is poured to form the new large concrete tower foundation of the embodiment of the present invention.

[0063] The original foundation bottom plate steel bars of the present invention maintain the original configuration, a new foundation is cast outside the original foundation, and the new and old foundations are connected by planting steel bars; the present invention sets a prestressed anchor cable force steering device in the foundation, making use of the original foundation cavity and the original anchor cable channel in the foundation, and can transfer the tension force of the prestressed anchor cable in the direction, so that the original anchor cable prestressed channel is effectively used. Compared with the existing technology, in the upgrading and reconstruction project, the present invention can make full use of the existing mixed tower foundation, effectively reducing the engineering cost and construction period.

[0064] For example, a 2.5MW wind turbine is upgraded to a 7.25MW unit. The original foundation is a 15-meter-diameter truncated cone gravity foundation. The original foundation steel reinforcement concrete consumption is about 400m 3 If the traditional technology of dismantling the newly reduced or enlarged section is adopted, the wind load bending moment will be about 3 times of the original bending moment after the 2.5MW unit is upgraded to a 7.25MW unit, the diameter of the new foundation will be about 20 meters, and the amount of reinforced concrete will be about 800m 3 The technical solution of the present invention is adopted, and the newly built foundation fully utilizes the original small concrete tower foundation, and the amount of reinforced concrete added to the foundation is about 500m 3 , saving 300m3 of reinforced concrete compared with conventional technology 3 , saving about 37.5% of the engineering workload, with obvious results.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An in-situ transformation of a concrete tower foundation, characterized in that: It includes an original small concrete tower foundation and a newly established foundation. The newly established foundation is formed by casting on the outer surface of the original small concrete tower foundation by a restricted expansion section method. A prestressed anchor cable force steering device is arranged in the newly established foundation to transfer the direction of the prestressed anchor cable tensioning force.

2. The in-situ transformation mixing tower foundation according to claim 1, characterized in that: The original small concrete tower foundation is formed of a bottom cylinder, a middle frustum and a top hollow cylinder in one piece; the newly-built foundation includes a new middle frustum and a new top hollow cylinder, and the connection between the new and old foundations is strengthened by embedded steel bars and an interface agent.

3. The in-situ transformation mixing tower foundation according to claim 2, characterized in that: The top hollow cylinder of the original small concrete tower foundation is removed within a height range and the original steel bars are retained, and are reused in the new top hollow cylinder of the newly established foundation.

4. The in-situ transformation mixing tower foundation according to claim 1, characterized in that: The outer surface of the original small concrete tower foundation is reinforced with 12mm diameter steel bars with a longitudinal and transverse interval of 300mm, and the embedded depth is not less than 250mm.

5. The in-situ transformation mixing tower foundation according to claim 1, characterized in that: The joint surface between the original small concrete tower foundation and the newly-built foundation is roughened, and an interface agent is applied before pouring to enhance the connection strength.

6. The in-situ transformation mixing tower foundation according to claim 1, characterized in that: The newly-established foundation is designed by a restricted extended section method, and the width is expanded outside the original small mixing tower foundation; The limiting principle of the restricted extended section method is that the steel bars of the original small concrete tower foundation maintain the original configuration and are connected with the steel bars in the newly established foundation.

7. The in-situ transformation mixing tower foundation according to claim 1, characterized in that: The prestressed anchor cable force steering device includes an upper steel pipe, a middle steel pipe, a lower steel pipe and a steering wheel; the upper steel pipe is buried in the newly established foundation, the lower steel pipe is nested in the prestressed anchor cable channel of the original small concrete tower foundation, the middle steel pipe is welded to connect the upper steel pipe and the lower steel pipe, and the steering wheel includes a fixed shaft and a movable wheel, and the movable wheel rotates around the fixed shaft to realize the direction transfer of the tensioning force of the prestressed anchor cable.

8. The in-situ transformation concrete tower foundation according to claim 7, characterized in that: The prestressed anchor cable force steering device also includes a sealing cover, which is used to prevent damage to the steering wheel during concrete pouring and provide protection against corrosion and environmental erosion; the sealing cover is made of high-strength composite material or corrosion-resistant metal.

9. The in-situ transformation concrete tower foundation according to claim 1, characterized in that: The prestressed anchor cable holes of the original small concrete tower foundation are retained and reused; the prestressed anchor cables in the new concrete tower foundation pass through the original anchor cable holes through the steering device and achieve effective direction transfer.

10. The construction method for in-situ transformation of a concrete tower foundation according to claim 1, characterized in that: The steps include: S1: The original hollow cylinder at the top of the existing small concrete tower foundation is removed within the height range, and the original steel bars are retained for reuse in the new concrete tower foundation; S2: The outer surface of the original small concrete tower foundation is treated with 12mm diameter steel bars at intervals of 300mm in the vertical and horizontal directions. The length of the steel bars in the new and old foundations is not less than 250mm. After the steel bars are planted on the surface of the original small concrete tower foundation, the surface is roughened and cleaned; S3: A new foundation is set on the outer surface of the original small concrete tower foundation. The interface agent is applied to the joint surface between the new foundation and the original small concrete tower foundation before the new foundation is poured. The width of the new foundation expanded outward from the original small concrete tower foundation, the height of the new middle frustum and the new top hollow cylinder, and the steel bars inside the new foundation are determined by finite element calculation. The principle of determination is that the steel bars inside the original small concrete tower foundation remain unchanged. S4: The force conversion of the prestressed anchor cable is carried out in the foundation. A prestressed anchor cable force steering device is arranged in the new foundation. The prestressed anchor cable force steering device transfers the direction of the tensioning force of the prestressed anchor cable through the movable wheel arranged inside, and the original prestressed hole of the anchor cable is effectively utilized.

Images