A monitoring method for prefabricated concrete tower barrel foundation

Abstract

The present invention belongs to the technical field of wind power tower and tower foundation monitoring, and discloses a method for monitoring the foundation of an assembled concrete tower. According to the determined four measuring point positions, an earth pressure gauge is set at the bottom of the foundation slab, and at least one strain gauge measuring point is set at each measuring point position on the top annular ribs, top radial ribs, bottom annular ribs, bottom radial ribs, truncated cone vertical ribs and corbel corner ribs of the foundation slab, and in the surrounding concrete; after the strain gauge measuring points are grouped, they are connected to a signal acquisition device through a junction box at the corresponding measuring point position; after pouring the foundation concrete, the signal acquisition device performs data acquisition and monitors the detection data of the strain gauge measuring points and the earth pressure gauge. The present invention can monitor the internal forces of the foundation slab, corbel corner ribs and truncated cone vertical ribs and the settlement of the foundation slab, thereby realizing real-time health monitoring of the foundation.

Description

Technical Field

[0001] The present invention relates to the technical field of monitoring of wind power tower barrels and tower barrel foundations, and particularly relates to a monitoring method for an assembled concrete tower barrel foundation. Background Art

[0002] Wind power projects are gradually developing towards low-wind-speed and high-shear regions. The height of the tower barrels of wind turbines is gradually increasing from below 100m to 120m, 140m or even higher. In the tower barrels of wind turbines above 100m, due to defects such as light weight, small stiffness, small damping, and easy resonance with the working frequency of the fan caused by the traditional steel tower barrels, the advantages of concrete tower barrels have been further manifested and are more and more widely used.

[0003] Considering factors such as quality and construction period, at present, concrete tower barrels generally adopt an assembled form. The tower barrel sections are prefabricated in the factory, assembled section by section on site, and finally the entire fan tower barrel structure is formed by means of prestressed anchor cable tensioning and anchoring.

[0004] Due to the mechanical properties and construction requirements of the assembled concrete tower barrel, there is a large frustum-shaped cavity at the bottom of the tower barrel foundation for installing prestressed anchor cables; there is a structure similar to a corbel at the foundation for fixing the prestressed anchor cables; the upper assembled tower barrel is connected to the foundation through a cast-in-place concrete tower barrel section, and the load is transmitted to the foundation through the cast-in-place concrete tower barrel section. In the prior art, there is a lack of a method for monitoring the frustum-shaped cavity foundation, so the health assessment of the tower barrel cannot be carried out. Summary of the Invention

[0005] The purpose of the present invention is to provide a monitoring method for an assembled concrete tower barrel foundation to solve the problem of health monitoring of the assembled concrete tower barrel foundation of a wind turbine.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A monitoring method for an assembled concrete tower barrel foundation includes the following steps:

[0008] S1, setting the measuring point azimuth: Four measuring point azimuths are set on the side facing the main wind direction, the side opposite to the main wind direction, and the two sides perpendicular to the main wind direction;

[0009] S2, arranging earth pressure cells at the bottom of the foundation slab, and at least one earth pressure cell is arranged at each of the measuring point azimuths;

[0010] S3. On the circumferential bars at the top of the base slab, the radial bars at the top of the base slab, the circumferential bars at the bottom of the base slab, the radial bars at the bottom of the base slab, the vertical bars of the frustum, and the corner bars of the corbel, at least one strain gauge measuring point is respectively arranged at each measuring point azimuth; in the concrete around the circumferential bars at the top of the base slab, the radial bars at the top of the base slab, the circumferential bars at the bottom of the base slab, the radial bars at the bottom of the base slab, and the vertical bars of the frustum, at least one strain gauge measuring point is respectively arranged at each measuring point azimuth;

[0011] S4. Group the strain gauge measuring points:

[0012] The first group includes the strain gauge measuring points on the circumferential bars at the top of the base slab and the radial bars at the top of the base slab, and the strain gauge measuring points in the concrete around the circumferential bars at the top of the base slab and the radial bars at the top of the base slab; the second group includes the strain gauge measuring points on the circumferential bars at the bottom of the base slab and the radial bars at the bottom of the base slab, and the strain gauge measuring points in the concrete around the circumferential bars at the bottom of the base slab and the radial bars at the bottom of the base slab; the third group includes the strain gauge measuring points on the vertical bars of the frustum and the corner bars of the corbel, and the strain gauge measuring points in the concrete around the vertical bars of the frustum; the wires of the strain gauge measuring points in each group are respectively led into the junction box at the corresponding measuring point azimuth and are connected to the signal acquisition device through the junction box;

[0013] S5. After pouring the foundation concrete, the signal acquisition device performs data acquisition to monitor the detection data of the strain gauge measuring points and the earth pressure gauges.

[0014] Optionally, the strain gauge measuring points on the circumferential bars at the top of the base slab, the radial bars at the top of the base slab, the circumferential bars at the bottom of the base slab, and the radial bars at the bottom of the base slab are all arranged close to the outer edge of the frustum where the vertical bars of the frustum are located.

[0015] Optionally, in step S2, two earth pressure gauges are arranged at each measuring point azimuth, and the two earth pressure gauges are arranged at intervals at both ends of the base slab at the outer side part of the vertical bars of the frustum.

[0016] Optionally, the earth pressure gauge and the device for measuring strain are at the same vertical position.

[0017] Optionally, the position of the strain gauge measuring point on the vertical bars of the frustum is close to the cast-in-place tower barrel section to detect the local load level below the cast-in-place tower barrel section.

[0018] Optionally, the measuring direction of the strain gauge at the strain gauge measuring point is along the axial direction of the radial bar at the bottom of the base slab or the radial bar at the top of the base slab, or along the tangent direction of the circumferential bar at the top of the base slab or the circumferential bar at the bottom of the base slab.

[0019] Optionally, the strain gauges at the strain gauge measuring points are all tied to the top plate circumferential reinforcement, the top plate radial reinforcement, the bottom plate circumferential reinforcement, the bottom plate radial reinforcement, the frustum vertical reinforcement, and the corbel corner reinforcement. There are cushion blocks between the strain gauges at the strain gauge measuring points in the surrounding concrete and the top plate circumferential reinforcement, the top plate radial reinforcement, the bottom plate circumferential reinforcement, the bottom plate radial reinforcement, and the frustum vertical reinforcement at the corresponding positions.

[0020] Optionally, the detection data of the strain gauge measuring points in step S5 includes the strain data directly detected and the stress data calculated based on the strain data.

[0021] Optionally, the monitoring in step S5 further includes monitoring the sectional moment of the foundation slab, and the sectional moment is obtained by the following method:

[0022] S51. Select a certain moment before the installation of the fan tower and after the foundation concrete is poured and cured. Select the values of the strain gauge measuring points at the same measuring point azimuth at this time as the reference points, and assume them to be ε 0，i , i = 1, 2, 3, 4;

[0023] S52. Subtract the strain value ε i measured at any moment of the same strain gauge measuring point from the strain reference point ε 0，i at the same moment to obtain the strain value Δε caused by the external load at any moment; then the steel bar stress value caused by the external load is Δσ S = E·Δε, and the concrete stress value Δσ C = σ(Δε); the steel bars include the top plate circumferential reinforcement, the top plate radial reinforcement, the bottom plate circumferential reinforcement, and the bottom plate radial reinforcement; thus, Δσ CDHTi , Δσ SDHTi , and Δσ SDHBi are respectively the stresses of the concrete around the top plate circumferential reinforcement, the stress of the top plate circumferential reinforcement, and the stress of the bottom plate circumferential reinforcement, and Δσ CDJTi , Δσ SDJTi , and Δσ SDJBi are respectively the stresses of the concrete around the top plate radial reinforcement, the stress of the top plate radial reinforcement, and the stress of the bottom plate radial reinforcement;

[0024] S53. The steel bars and the concrete around the steel bars form an equivalent beam. The strain of the concrete in the compression zone of the equivalent beam section is linearly distributed along the height x of the compression zone. The stress Δσ xi at any point on the height x of the compression zone is = σ(Δε xi ), then the sectional moment M of the foundation slab is:

[0025] M = F CDHTi(CDJTi)(h 0 -x + y c ) + A ST nΔσ SDHTi(SDJTi) (h 0 -a s )

[0026] Wherein, F CDHTi(CDJTi) is the resultant force of the compressive stress in the compression zone; When calculating the circumferential bending moment, there is Δε xi = Δε CDHTi * xi / x; when calculating the radial bending moment, there is Δε xi = Δε CDJTi * xi / x; xi is the distance from the calculation point to the neutral axis; Δε CDJTi is the strain of the concrete around the radial bars at the top of the slab, and Δε CDHTi is the strain of the concrete around the circumferential bars at the top of the slab; h 0 is the effective height of the equivalent beam section, and a s is the distance from the resultant force point of the compressive reinforcement in the compression zone to the compression edge of the section; y c is the distance from the resultant force point of the concrete compressive stress to the neutral axis; b is the bar spacing of the circumferential bars at the bottom of the slab, the circumferential bars at the top of the slab, the radial bars at the bottom of the slab, or the radial bars at the top of the slab; A ST is the cross-sectional area of a single bar of the circumferential bars at the top of the slab or the radial bars at the top of the slab.

[0027] Optionally, the monitoring in step S5 further includes monitoring the axial force of the vertical bars of the frustum. The axial force F YT of the vertical bars of the frustum is:

[0028] F YT = A YTS Δσ S

[0029] Wherein, A YTS is the cross-sectional area of the steel bars of the vertical bars of the frustum.

[0030] Advantages of the present invention:

[0031] A monitoring method for an assembled concrete tower barrel foundation of the present invention can monitor the internal forces of the foundation slab, the corner bars of the corbel, and the vertical bars of the frustum and the settlement of the foundation slab by respectively arranging strain gauge measuring points at four measuring point positions on the top and bottom steel bars of the foundation slab, thereby realizing real-time health monitoring of the foundation. Description of the drawings

[0032] Figure 1 is a plan view of the foundation slab in a monitoring method for an assembled concrete tower barrel foundation of the present invention;

[0033] Figure 2 It is a schematic diagram of the plane arrangement of earth pressure gauges in a method for monitoring a prefabricated concrete tower foundation of the present invention;

[0034] Figure 3 yes Figure 1 AA cross-section diagram, including Figure 2 The earth pressure gauge TYL shown;

[0035] Figure 4 is a schematic diagram of an equivalent beam structure consisting of steel bars and concrete surrounding the steel bars in an embodiment of the present invention;

[0036] Figure 5 yes Figure 4 Schematic diagram of cross-sectional stress of equivalent beam;

[0037] Figure 6 yes Figure 4 Schematic diagram of the cross-sectional strain of the equivalent beam.

[0038] In the figure:

[0039] 1. Foundation slab; 11. Circumferential reinforcement at the top of the slab; 12. Radial reinforcement at the top of the slab; 13. Circumferential reinforcement at the bottom of the slab; 14. Radial reinforcement at the bottom of the slab; 2. Vertical reinforcement of the truncated cone; 3. Reinforcement at the corners of the corbel; 4. Cast-in-place tower section; 5. Junction box. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0041] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0043] In the description of this embodiment, the orientation or positional relationships such as "upper", "lower", "right", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of description and simplifying the operation, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0044] The present invention provides a monitoring method for an assembled concrete tower barrel foundation, as Figure 3 shown. The assembled concrete tower barrel foundation includes a foundation bottom plate 1, a frustum section and an anchor cable anchorage section. Among them, before pouring concrete for the foundation bottom plate 1, circumferential bars 11 at the top of the plate, radial bars 12 at the top of the plate, circumferential bars 13 at the bottom of the plate and radial bars 14 at the bottom of the plate need to be provided. The frustum section is provided with frustum vertical bars 2, and the anchor cable anchorage section is provided with bracket corner bars 3. The cast-in-place tower barrel section 4 is poured on the top of the frustum section. In this embodiment, the frustum section is a cylindrical ring structure above the foundation bottom plate 1, which is generally called a frustum in the art. Applying the monitoring method provided by the present invention, the monitoring contents include the strains of the circumferential bars 11 at the top of the plate, the radial bars 12 at the top of the plate, the circumferential bars 13 at the bottom of the plate and the radial bars 14 at the bottom of the plate, the strains of the top and bottom concrete of the foundation bottom plate 1, the strains of the frustum vertical bars 2 and the bracket corner bars 3, the strains of the concrete around the frustum vertical bars 2 and the bracket corner bars 3, and the settlement of the foundation bottom plate 1, which are respectively used to reflect the internal force of the foundation bottom plate 1, the local compression (below the cast-in-place tower barrel section 4) of the frustum section, the internal force level of the local tension of the bracket, the settlement and inclination of the foundation, so as to realize the health monitoring of the assembled concrete tower barrel foundation.

[0045] As Figures 1-3 shown, a monitoring method for an assembled concrete tower barrel foundation provided in this embodiment includes the following steps:

[0046] S1, setting the measuring point orientation: Four measuring point orientations are set on the side facing the main wind direction, the side facing away from the main wind direction and the two sides perpendicular to the main wind direction; these four measuring point orientations can fully reflect the foundation stress state under the main wind direction condition, and have more significant representativeness and researchability.

[0047] S2. Install earth pressure gauges TYL at the bottom of the base slab 1, with at least one earth pressure gauge TYL arranged at each measuring point orientation.

[0048] As Figure 2 shown in the embodiment, before installing the base slab 1, pre-survey the outline of the base slab 1 to determine the measuring point orientation, and then bury the earth pressure gauges TYL. Two earth pressure gauges TYL are arranged at each measuring point orientation, for a total of eight. The two earth pressure gauges TYL are arranged at intervals at both ends of the base slab 1 on the outer part of the vertical bars 2 of the frustum. The earth pressure gauges TYL are used to measure the compressive stress of the soil below the foundation. When arranging, two earth pressure gauges TYL are arranged at each measuring point orientation. One earth pressure gauge TYL is arranged at the bottom of the outermost edge of the base slab 1, that is, the end of the center, and the other earth pressure gauge TYL is arranged at a position close to the frustum section or close to the center of the base slab 1, so as to more comprehensively reflect the distribution law of the earth pressure along the radial direction of the foundation ring. The earth pressure gauges TYL are in the same vertical position as the equipment for measuring strain. The equipment for measuring strain includes the equipment for measuring the strain of the internal steel bars and concrete of the base slab 1. As Figure 2 and Figure 3 shown, the eight earth pressure gauges TYL are distributed in central symmetry and axial symmetry.

[0049] S3. At the circumferential bars 11, radial bars 12, bottom circumferential bars 13, bottom radial bars 14, vertical bars 2 of the frustum and corner bars 3 of the corbel on the top of the base slab 1, at least one strain gauge measuring point is respectively arranged at each measuring point orientation; in the concrete around the circumferential bars 11, radial bars 12, bottom circumferential bars 13, bottom radial bars 14 and vertical bars 2 of the frustum on the top of the base slab 1, at least one strain gauge measuring point is respectively arranged at each measuring point orientation;

[0050] At each strain gauge measuring point in the present invention, a strain gauge or a strain gauge is provided. The strain gauge or the strain gauge is installed on the steel bars of the foundation and is poured into the foundation together with the steel bars.

[0051] Combined with Figure 1 and Figure 3, one strain gauge measuring point DH is set at each measuring point azimuth on the top-ring reinforcement 11 and bottom-ring reinforcement 13 of the slab, with a total of eight. One strain gauge measuring point DJ is set at each measuring point azimuth on the top-radial reinforcement 12 and bottom-radial reinforcement 14 of the slab, with a total of eight. Relative to the edge of the foundation slab 1, the eight strain gauge measuring points DH and the eight strain gauge measuring points DJ are both set close to the outer edge of the frustum where the frustum vertical reinforcement 2 is located, at least at one-third of the distance from the outer edge of the frustum section to the outer edge of the foundation slab 1, that is, within the circumferential reinforcement range within ten of the frustum outer edge. If the foundation slab 1 is equivalent to a cantilever beam stress model, the frustum section can be regarded as a support, where the internal force is the largest, so it should be monitored keyly. Therefore, the strain gauge measuring points DH and the strain gauge measuring points DJ are both arranged close to the outer edge of the frustum section, and the measured data of the measuring points can corroborate each other.

[0052] Optionally, the strain gauge measuring point YT on the frustum vertical reinforcement 2 is set close to the cast-in-situ tower barrel section 4 to detect the local load level below the cast-in-situ tower barrel section 4. As Figure 1 and Figure 3 shown, one strain gauge measuring point YT is set at each measuring point azimuth, with a total of four. The strain gauge measuring point YT is set on the frustum vertical reinforcement 2 below the cast-in-situ tower barrel section 4, and the strain gauge measuring point YT is set close to the cast-in-situ tower barrel section 4 to fully reflect the load level and influence of the cast-in-situ tower barrel section 4 on the local compression of the foundation.

[0053] On the bracket corner reinforcement 3, one strain gauge measuring point NT is set at each measuring point azimuth respectively, with a total of four. As Figure 1 and Figure 3 shown, the bracket corner reinforcement 3 is set in the cable anchor section, and the strain gauge measuring point NT can fully reflect the load level and influence of the bracket under the tension of the prestressed cable.

[0054] In this embodiment, the purpose of setting the strain gauge measuring points in the concrete is to measure the concrete strain between the steel bar and the foundation surface. The general method for measuring concrete strain in the prior art is to paste strain gauges on the foundation surface. However, in a complex soil environment, the strain gauges are extremely easy to be damaged during the backfilling construction after the foundation installation is completed, and the measurement result of the concrete strain is easily affected by soil disturbance. Therefore, in the present invention, strain gauge measuring points are respectively set between the top-ring reinforcement 11, bottom-ring reinforcement 12, bottom-ring reinforcement 13, bottom-radial reinforcement 14, frustum vertical reinforcement 2 of the slab and the concrete between the foundation surface, and strain gauges are arranged at the strain gauge measuring points, preferably vibrating wire concrete strain gauges.

[0055] During installation, for the purpose of distinction, in the present invention, the strain gauge used to measure the strain of steel bars is called the steel bar strain gauge, and the strain gauge used to measure the strain of concrete is called the concrete strain gauge. When installing the steel bar strain gauge and the concrete strain gauge, they are tied to the same steel bar at the same measuring point orientation, and the concrete strain gauge is arranged adjacent to the steel bar strain gauge. The measuring points of the strain gauges at the same measuring point orientation are preferably arranged at the same vertical position. In the macroscopic foundation, the volume of the strain gauge is very small and can be equivalent to a point. Therefore, arranging them adjacent can ensure that the steel bar strain gauge and the concrete strain gauge can reflect the stress changes within the same cross-section. The measuring directions of the concrete strain gauge and the steel bar strain gauge are the same, either the tangent direction of the circumferential bars at the top or bottom of the slab, or the axial direction of the radial bars at the top or bottom of the slab.

[0056] Optionally, all the steel bar strain gauges at the measuring points of the strain gauges are tied to the circumferential bars 11 at the top of the foundation slab 1, the radial bars 12 at the top of the slab, the circumferential bars 13 at the bottom of the slab, the radial bars 14 at the bottom of the slab, the vertical bars 2 of the frustum, and the corner bars 3 of the corbel. At the measuring points of the concrete strain gauges in the surrounding concrete, there are spacer blocks between the concrete strain gauges and the circumferential bars 11 at the top of the slab, the radial bars 12 at the top of the slab, the circumferential bars 13 at the bottom of the slab, the radial bars 14 at the bottom of the slab, and the vertical bars 2 of the frustum, and they are tied to the same steel bar at the corresponding positions. There are spacer blocks placed between the concrete strain gauge and the attached steel bar, so that the concrete strain gauge can be as close as possible to the concrete surface to measure the concrete stress on the surface of the foundation.

[0057] S4. Group the measuring points of the strain gauges:

[0058] The first group includes the measuring points of the strain gauges on the circumferential bars 11 at the top of the foundation slab 1 and the radial bars 12 at the top of the slab, and the measuring points of the strain gauges in the surrounding concrete of the circumferential bars 11 at the top of the slab and the radial bars 12 at the top of the slab; the second group includes the measuring points of the strain gauges on the circumferential bars 13 at the bottom of the foundation slab 1 and the radial bars 14 at the bottom of the slab, and the measuring points of the strain gauges in the surrounding concrete of the circumferential bars 13 at the bottom of the slab and the radial bars 14 at the bottom of the slab; the third group includes the measuring points of the strain gauges on the vertical bars 2 of the frustum and the corner bars 3 of the corbel, and the measuring points of the strain gauges in the surrounding concrete of the vertical bars 2 of the frustum. The wires of the measuring points of each group of strain gauges are respectively led into the junction box 5 at the corresponding measuring point orientation and are connected to the signal acquisition device through the junction box 5.

[0059] As Figure 1 and Figure 3 shown, the junction box 5 is in Figure 1Indicated by JXX, one is set at each of the four measuring points, and the specific height position is not limited. The junction box 5 at each measuring point is used to concentrate the wires of the strain gauge measuring point at the corresponding measuring point. During implementation, the strain gauge or strain gauge set at the strain gauge measuring point, as well as the earth pressure gauge, etc., have their wires or cables tied along the direction of the attached steel bars, and a reserved length is extended to the outside of the foundation. The cables are tied close to the steel bars to avoid winding damage during concrete construction. A fixed bracket with a container 5 is tied and installed on the steel bars of the foundation, and a fixed bracket is arranged at each of the four measuring points to fix the container 5. When concrete is constructed and poured near the strain gauge and strain gauge, vibration with a vibrating rod should be avoided, and manual vibration should be adopted to avoid damage to the detection equipment. After the concrete strength reaches the design requirements, the junction box 5 is installed on the fixed bracket of the junction box 5. A cable through hole is left on the lower side of the junction box 5, and the cables of the strain gauge or strain gauge and the earth pressure gauge enter the interior of the junction box 5 through the cable through hole. A small door is provided on the side of the junction box 5 facing away from the base surface, and a wiring hole is provided on the door. The lead-out cables of the junction box 5 can be introduced through the wiring hole and connected to the signal acquisition device.

[0060] S5, after pouring the foundation concrete, the signal acquisition device collects data and monitors the detection data of the strain gauge measuring points and the earth pressure gauge.

[0061] Optionally, the detection values ​​of the strain gauge and the earth pressure gauge at any time can be read through the signal acquisition device to obtain the strain time history curve of the strain gauge measuring point at each measuring point, thereby realizing the monitoring of the foundation strain level. According to the constitutive relationship of the foundation (prefabricated concrete tower foundation, referred to as the foundation, the foundation includes the foundation bottom plate 1.), the stress of each part of the foundation bottom plate 1 can be calculated by strain, and then the internal force of each part of the foundation bottom plate 1 can be obtained. When the internal force of the foundation bottom plate 1 exceeds the design value, a corresponding early warning or alarm is issued.

[0062] In the embodiment of the present invention, the detection data of the strain gauge measuring point in step S5 includes strain data obtained by direct detection and stress data calculated according to the strain data.

[0063] Optionally, the monitoring in step S5 includes monitoring the cross-sectional bending moment of the foundation slab 1 and monitoring the axial force of the truncated cone vertical ribs 2 .

[0064] The section bending moment of the foundation slab 1 is obtained by the following method:

[0065] S51, select a time before the installation of the wind turbine tower and after the foundation concrete is poured and cured for 14 days, and select the value of the strain gauge measuring point at the same measuring point as the reference point, assuming ε 0，i , i=1,2,3,4;

[0066] S52. Subtract the strain value ε measured at any moment at the same strain gauge measurement point i from the strain reference point ε at the same moment 0，i to obtain the strain value Δε caused by the external load at any moment; then the steel bar stress value caused by the external load is Δσ S = E·Δε, and the concrete stress value Δσ C = σ(Δε); the concrete stress value Δσ C is calculated using the concrete constitutive relationship in Article 3, Section 6.2.1 of the "Code for Design of Concrete Structures". The concrete stress is a function of the concrete strain, and the steel bar stress is a function of the steel bar strain.

[0067] As used herein, the term "steel bar" generally refers to all steel bar materials, including the circumferential bars 11 at the top of the slab, the radial bars 12 at the top of the slab, the circumferential bars 13 at the bottom of the slab, the radial bars 14 at the bottom of the slab, as well as the vertical bars 2 of the frustum and the corner bars 3 of the corbel in the basic steel bar framework.

[0068] According to the stress-strain relationship, it can be calculated that Figure 5 where: Δσ CDHTi , Δσ SDHTi , Δσ SDHBi are respectively the stresses of the concrete around the circumferential bar 11 at the top of the slab, the stress of the circumferential bar 11 at the top of the slab, and the stress of the circumferential bar 13 at the bottom of the slab, and Δσ CDJTi , Δσ SDJTi , Δσ SDJBi are respectively the stresses of the concrete around the radial bar 12 at the top of the slab, the stress of the radial bar 12 at the top of the slab, and the stress of the radial bar 14 at the bottom of the slab;

[0069] S53. The steel bar and the concrete around it form an equivalent beam as Figure 4 . In the figure, the dots represent the steel bars, and the rectangular frames are the concrete. The stress distribution and strain distribution of the steel bar and the concrete at the strain gauge measurement point are as Figure 5 and Figure 6 . Figure 6 where Δε CDHTi is the strain of the concrete around the circumferential bar 11 at the top of the slab, Δε SDHTi is the strain of the circumferential bar 11 at the top of the slab, Δε SDHBi is the strain of the circumferential bar 13 at the bottom of the slab, Δε CDJTi is the strain of the concrete around the radial bar 12 at the top of the slab, Δε SDJTi is the strain of the radial bar 12 at the top of the slab, Δε SDJBi is the strain of the radial bar 14 at the bottom of the slab, i represents the azimuth of the i-th measurement point, and H is the distance between the top and bottom of the foundation slab 1. The strain of the concrete in the compression zone of the equivalent beam section is linearly distributed along the height x of the compression zone, and the stress Δσ xi = σ(Δε xi ) at any point on the height x of the compression zone. Then the section moment M of the foundation slab is:

[0070] M = F CDHTi(CDJTi) (h 0 -x + y c ) + A ST nΔσ SDHTi(sDJTi) (h 0 -a s )

[0071] In the formula, F CDHTi(CDJTi) is the resultant force of the compressive stress in the concrete compression zone (including the concrete pressure around the circumferential reinforcement 11 at the top of the slab and the radial reinforcement 12 at the top of the slab). When calculating the circumferential bending moment, there is Δε xi = Δε CDHTi *xi / x; when calculating the radial bending moment, there is Δε xi = Δε CDJTi *xi / x; xi is the distance from the calculation point to the neutral axis; Δε CDJTi is the strain of the concrete around the radial reinforcement 12 at the top of the slab, and Δε CDHTi is the strain of the concrete around the circumferential reinforcement 11 at the top of the slab; h 0 is the effective height of the equivalent beam section, and a s is the distance from the resultant force point of the compressive reinforcement to the compressive edge of the equivalent beam section; y c is the distance from the resultant force point of the concrete compressive stress to the neutral axis and can be obtained by integration; b is the reinforcement spacing of the circumferential reinforcement 13 at the bottom of the slab, the circumferential reinforcement 11 at the top of the slab, the radial reinforcement 14 at the bottom of the slab, or the radial reinforcement 12 at the top of the slab, with the unit of m.

[0072] Among them, the height of the compression zone of the equivalent beam cross-section is calculated using the formula:

[0073]

[0074] Among them, A ST is the cross-sectional area of a single reinforcement of the circumferential reinforcement 11 at the top of the slab or the radial reinforcement 12 at the top of the slab, and A SB is the cross-sectional area of a single reinforcement of the circumferential reinforcement 13 at the bottom of the slab or the radial reinforcement 14 at the bottom of the slab.

[0075] Optionally, in step S5, the monitoring further includes monitoring the axial force of the frustum vertical reinforcement 2, and the specific calculation method of the axial force F of the frustum vertical reinforcement 2 is as follows: YT A. Select a certain moment after the installation of the wind turbine tower barrel and 14 days after the completion of the foundation concrete pouring and curing. Select the values of each strain gauge at the same layout point, i.e., the measuring point orientation, at this time as the reference points, and assume them to be ε

[0076] (i = 1, 2, 3, 4). 0，i (i = 1, 2, 3, 4).

[0077] B. Subtract the strain value ε measured by each strain gauge at the same position at any time i from the strain reference point ε at the same time 0，i , and the strain value Δε caused by the external load at any time can be obtained. Then the steel bar stress value caused by the external load is Δσ S = E·Δε, and the concrete stress value Δσ C can be calculated by using the concrete constitutive relationship in Article 3 of Section 6.2.1 of the "Code for Design of Concrete Structures", Δσ C = σ(Δε).

[0078] C. From this, the axial force F of the frustum vertical bar 2 can be obtained YT as:

[0079] F YT = A YTS Δσ S

[0080] where A YTS is the cross-sectional area of the steel bar of the frustum vertical bar 2.

[0081] When the axial force borne by the frustum section exceeds the design value, corresponding early warning or alarm processing is carried out.

[0082] A monitoring method for an assembled concrete tower barrel foundation provided by the present invention can monitor the internal forces of the foundation bottom plate 1, the corbel corner bar 3 and the frustum vertical bar 2, and monitor the settlement amount of the foundation bottom plate 1 by respectively arranging strain gauge measuring points at four measuring point positions on the top and bottom steel bars of the foundation bottom plate 1, so as to realize real-time health monitoring of the foundation.

[0083] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation manner of the present invention. For those of ordinary skill in the art, various obvious changes, re-adjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for monitoring the foundation of an assembled concrete tower. It is characterized in that The steps include: S1, measuring point orientation setting: set four measuring points in the direction facing the main wind, the direction away from the main wind, and on both sides perpendicular to the main wind direction; S2, arranging an earth pressure gauge at the bottom of the foundation slab (1), with at least one earth pressure gauge being arranged at each measuring point; S3, on the slab top annular reinforcement (11), the slab top radial reinforcement (12), the slab bottom annular reinforcement (13), the slab bottom radial reinforcement (14), the truncated cone vertical reinforcement (2) and the corbel corner reinforcement (3) of the foundation slab (1), at least one strain gauge measuring point is respectively arranged at each of the measuring point orientations; in the concrete surrounding the slab top annular reinforcement (11), the slab top radial reinforcement (12), the slab bottom annular reinforcement (13), the slab bottom radial reinforcement (14) and the truncated cone vertical reinforcement (2), at least one strain gauge measuring point is respectively arranged at each of the measuring point orientations; S4, grouping the strain gauge measuring points: The first group includes the strain gauge measuring points on the plate top annular ribs (11) and the plate top radial ribs (12) of the base bottom plate (1), and the strain gauge measuring points in the concrete around the plate top annular ribs (11) and the plate top radial ribs (12); the second group includes the strain gauge measuring points on the plate bottom annular ribs (13) and the plate bottom radial ribs (14) of the base bottom plate (1), and the strain gauge measuring points in the concrete around the plate bottom annular ribs (13) and the plate bottom radial ribs (14); the third group includes the strain gauge measuring points on the truncated cone vertical ribs (2) and the corbel corner ribs (3), and the strain gauge measuring points in the concrete around the truncated cone vertical ribs (2); the wires of each group of the strain gauge measuring points are respectively led into the junction box (5) at the corresponding measuring point orientation, and are connected to the signal acquisition device through the junction box (5); S5, after pouring the foundation concrete, the signal acquisition device performs data acquisition and monitors the detection data of the strain gauge measuring point and the earth pressure gauge; The monitoring further includes monitoring the cross-sectional bending moment of the foundation slab (1), wherein the cross-sectional bending moment is obtained by the following method: S51. Select a certain moment after the completion and curing of the foundation concrete before the installation of the wind turbine tower. Select the value of the strain gauge measurement point at the same measurement point orientation at this time as the reference point, and assume it as , where i = 1, 2, 3, 4; S52, subtract the strain value measured at any moment of the same strain gauge measurement point from the strain reference point at the same moment to obtain the strain value caused by the external load at any moment ; then the steel bar stress value caused by the external load is △ , and the concrete stress value is △ ; the steel bars include the top - plate circumferential bars (11), the top - plate radial bars (12), the bottom - plate circumferential bars (13) and the bottom - plate radial bars (14); thus, the calculated , , are respectively the stress of the concrete around the top - plate circumferential bar (11), the stress of the top - plate circumferential bar (11) and the stress of the bottom - plate circumferential bar (13), , , are respectively the stress of the concrete around the top - plate radial bar (12), the stress of the top - plate radial bar (12) and the stress of the bottom - plate radial bar (14); S53. The steel bars and the concrete around the steel bars form an equivalent beam. The strain of the concrete in the compression zone of the equivalent beam cross-section is linearly distributed along the height x of the compression zone, and the stress at any point on the height x of the compression zone , then the cross-section moment M of the foundation slab (1) is as follows: M= ； In the formula, is the resultant force of the compressive stress in the compression zone, ; when calculating the circumferential bending moment, there is ; when calculating the radial bending moment, there is ; is the distance from the calculation point to the neutral axis; is the strain of the concrete around the radial reinforcement (12) at the top of the slab, is the strain of the concrete around the circumferential reinforcement (11) at the top of the slab, is the effective height of the equivalent beam section, is the distance from the resultant force point of the compressive reinforcement in the compression zone to the compression edge of the section; is the distance from the resultant force point of the concrete compressive stress to the neutral axis; , where b is the reinforcement spacing of the circumferential reinforcement (13) at the bottom of the slab, the circumferential reinforcement (11) at the top of the slab, the radial reinforcement (14) at the bottom of the slab, or the radial reinforcement (12) at the top of the slab; is the cross-sectional area of a single reinforcement bar of the circumferential reinforcement (11) or the radial reinforcement (12) at the top of the slab.

2. The method for monitoring the foundation of an assembled concrete tower according to claim 1, It is characterized in that The strain gauge measuring points on the plate top annular ribs (11), the plate top radial ribs (12), the plate bottom annular ribs (13), and the plate bottom radial ribs (14) are all arranged close to the outer edge of the truncated cone where the truncated cone vertical ribs (2) are located.

3. The method for monitoring the foundation of an assembled concrete tower according to claim 1, It is characterized in that In step S2, two earth pressure gauges are arranged at each measuring point, and the two earth pressure gauges are arranged at intervals at two ends of the foundation bottom plate (1) on the outer side of the truncated cone vertical rib (2).

4. The method for monitoring the foundation of an assembled concrete tower according to claim 3, It is characterized in that The earth pressure gauge is in the same vertical position as the device for measuring strain.

5. The monitoring method for the prefabricated concrete tower barrel foundation according to claim 1, characterized in that, the strain gauge measurement points on the frustum vertical reinforcement (2) are arranged close to the cast-in-place tower barrel section (4) to detect the local load level below the cast-in-place tower barrel section (4).

6. The monitoring method for the prefabricated concrete tower barrel foundation according to claim 1, characterized in that, the measuring direction of the strain gauge at the strain gauge measurement point is along the axial direction of the bottom plate radial reinforcement (14) or the top plate radial reinforcement (12), or along the tangent direction of the top plate circumferential reinforcement (11) or the bottom plate circumferential reinforcement (13).

7. The monitoring method for the prefabricated concrete tower barrel foundation according to claim 6, characterized in that, the strain gauges at the strain gauge measurement points are all tied to the top plate circumferential reinforcement (11), the top plate radial reinforcement (12), the bottom plate circumferential reinforcement (13), the bottom plate radial reinforcement (14), the frustum vertical reinforcement (2) and the bracket corner reinforcement (3). There are cushion blocks between the strain gauges at the strain gauge measurement points in the surrounding concrete and the top plate circumferential reinforcement (11), the top plate radial reinforcement (12), the bottom plate circumferential reinforcement (13), the bottom plate radial reinforcement (14) and the frustum vertical reinforcement (2) at the corresponding positions.

8. The monitoring method for the prefabricated concrete tower barrel foundation according to claim 1, characterized in that, the detection data of the strain gauge measurement points in step S5 include the strain data directly detected and the stress data calculated based on the strain data.

9. The monitoring method for the prefabricated concrete tower barrel foundation according to claim 1, characterized in that, The monitoring described in step S5 also includes monitoring the axial force of the frustum vertical bars (2), and the axial force of the frustum vertical bars (2) is as follows: ； Among them, is the cross-sectional area of the steel bar of the frustum vertical bar (2).

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