Method and device for monitoring scouring depth of offshore wind power single pile foundation in real time

Abstract

The invention belongs to the technical field of offshore wind power engineering, and relates to a real-time monitoring method and device for the scouring depth of an offshore wind power single pile foundation. According to the invention, pore water pressure and total stress (the sum of effective stress and pore water pressure) of corresponding depths are monitored in real time through a pore water pressure sensor and a soil pressure sensor; the scouring depth is obtained by judging monitoring values of the pore water pressure sensor and the soil pressure sensor at the same height; the device is simple and reliable, scouring development can be monitored, the unit scouring state can be evaluated, and safety guarantee is provided for operation and maintenance of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of offshore wind power engineering, and relates to a method and device for real-time monitoring of the scour depth of a single pile foundation for offshore wind power. Background Art

[0002] As a clean energy source, offshore wind power has developed rapidly. In particular, the single pile foundation has become one of the main foundation forms for offshore wind turbines due to its relatively simple and economical construction method. However, the single pile foundation is long-term in a complex marine environment and is affected by natural factors such as wind, waves, and currents, posing great structural safety hazards. The seabed scour phenomenon is one of the most prominent problems among them.

[0003] Seabed scour refers to the erosion and movement of the soil on the seabed surface due to the continuous action of factors such as waves and tides, resulting in a gradual decrease in the embedment depth of the single pile foundation. As the embedment depth of the foundation decreases, the friction between the pile foundation and the seabed decreases, thereby reducing the bearing capacity of the foundation, which in turn affects the stability and safety of the entire wind turbine unit. The long-term scour effect will also cause the overall first-order natural vibration frequency of the wind turbine unit to decrease, increase the deformation of the unit, seriously affect the normal operation of the unit, and even may occur safety accidents such as foundation instability or structural damage.

[0004] Currently, the monitoring means for seabed scour mainly rely on regular scour surveys. By using underwater sonar detection, video inspection and other means, relevant data on seabed scour can be obtained. Although these means can provide certain scour information, they cannot achieve real-time monitoring and dynamic tracking of the development process of scour. And due to the complex marine environment, the high cost and technical difficulty of underwater detection equipment, the scour monitoring work faces great challenges.

[0005] Therefore, how to achieve real-time and effective monitoring of the offshore single pile foundation and timely obtain the dynamic information on the development of seabed scour to ensure the long-term safe operation of the wind turbine unit has become an urgent problem to be solved in the current technical field. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the prior art and provide a method and device for real-time monitoring of the scour depth of a single pile foundation for offshore wind power, which can realize the monitoring of the scour condition and evaluate the scour state of the unit.

[0007] To achieve the above object, the present invention adopts the following technical solutions:[[]]END]] In a first aspect, the present invention provides a real-time monitoring device for the scour depth of a monopile foundation of an offshore wind farm, including a square pipe which is arranged along the axial direction of the monopile foundation; a plurality of monitoring units are equidistantly arranged on the square pipe; each monitoring unit includes a pore water pressure sensor and an earth pressure sensor, and the pore water pressure sensor and the earth pressure sensor in each monitoring unit are arranged at the same height; the horizontal height of the uppermost monitoring unit is the same as the height of the foundation soil layer surface.

[0008] Preferably, there are a plurality of the square pipes; the horizontal distance between each of the plurality of square pipes and the monopile foundation is 1 to 3 m.

[0009] Preferably, the length of the square pipe is greater than the designed maximum scour depth of the monopile foundation.

[0010] Preferably, it includes a protective cover; the protective cover covers the outer wall of the square pipe 1.

[0011] Preferably, the surface of the protective cover is provided with a diversion groove.

[0012] Preferably, it includes a calibration module; the calibration module is connected to the square pipe.

[0013] In a second aspect, the present invention provides a real-time monitoring method for the scour depth of a monopile foundation of an offshore wind farm, specifically including the following steps: The monitoring units are sequentially numbered as the first monitoring unit, the second monitoring unit,..., the (n - 1)th monitoring unit, and the nth monitoring unit along the depth direction; When there is no scour, the calculation formula for the monitoring value of the nth pore water pressure sensor along the depth direction is:

[0014] In the formula, is the monitoring value of the nth pore water pressure sensor along the depth direction; is the unit weight of water; is the height of the foundation soil layer surface from the water level; is the distance between adjacent monitoring units; When there is no scour, the calculation formulas for the monitoring values of the earth pressure sensors along the depth direction are successively:

[0015]

[0016] In the formula, , , , ……, They are the monitoring values of the first, second, third, …, and nth earth pressure sensors in the depth direction before scouring occurs, respectively. , , …, They are the average effective unit weights of the first soil layer, the second soil layer, …, and the (n - 1)th soil layer, respectively. is the coefficient of earth pressure at rest; The first soil layer, the second soil layer, …, and the (n - 1)th soil layer respectively refer to the soil between the first monitoring unit and the second monitoring unit, the soil between the second monitoring unit and the third monitoring unit, …, and the soil between the (n - 1)th monitoring unit and the nth monitoring unit. When scouring occurs, when (n - 1) l < <n l , the calculation formula for the monitoring value of the (n + 1)th pore water pressure sensor in the depth direction is:

[0017] In the formula, is the monitoring value of the (n + 1)th pore water pressure sensor in the depth direction when scouring occurs; When scouring occurs, when (n - 1) l < <n l , the calculation formula for the monitoring value of the (n + 1)th earth pressure sensor in the depth direction is:

[0018]

[0019] In the formula, is the monitoring value of the (n + 1)th earth pressure sensor in the depth direction when scouring occurs; is the average effective unit weight of the nth soil layer; the nth soil layer is the soil between the nth monitoring unit and the (n + 1)th monitoring unit; By combining the above formulas, when (n - 1) l < <n l , the scouring depth is obtained as:

[0020] In the formula, is the scouring depth.

[0021] Preferably, it further includes: establishing a relationship curve between the average effective unit weight of the soil and the depth in the historical monitoring data; when scouring causes changes in the soil layer distribution, updating the average effective unit weight of the soil by interpolation according to the curve.

[0022] Preferably, when scouring occurs, the pore water pressure sensor value in the same monitoring unit is equal to the earth pressure sensor, and the scouring depth is greater than or equal to the depth where the monitoring unit is located.

[0023] Preferably, when scouring occurs, if the pore water pressure sensor value in the same monitoring unit is not equal to the earth pressure sensor, the scouring depth is less than the depth where the monitoring unit is located.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The present invention monitors the pore water pressure and total stress (the sum of effective stress and pore water pressure) at corresponding depths in real time through a pore water pressure sensor and an earth pressure sensor; the scouring depth is obtained by judging the monitoring values of the pore water pressure sensor and the earth pressure sensor at the same height; the device of the present invention is simple and reliable, can realize the monitoring of the development of scouring, evaluate the scouring state of the unit, and provide safety guarantee for the operation and maintenance of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a schematic structural diagram of a real-time monitoring device for the scouring depth of a single pile foundation of an offshore wind turbine of the present invention; Figure 2 is Figure 1 the top view of; Figure 3 is a schematic diagram when scouring occurs.

[0027] Wherein: 1, square pipe; 2, single pile foundation; 3, pore water pressure sensor; 4, earth pressure sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0029] Accordingly, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0030] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0031] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed during use, it is only for the convenience of describing the present invention and simplifying the description, 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 cannot be construed as a limitation of the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0032] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0033] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. 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 situations.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings: The first object of the present invention is to provide a real-time monitoring device for the scour depth of an offshore wind power monopile foundation, as Figures 1 to 3 shown, including a square pipe 1, the square pipe 1 is arranged along the axial direction of the monopile foundation 2; a plurality of monitoring units are equidistantly arranged on the square pipe 1; the monitoring unit includes a pore water pressure sensor 3 and an earth pressure sensor 4, and the pore water pressure sensor 3 and the earth pressure sensor 4 in each monitoring unit are arranged at the same height; the horizontal height of the uppermost monitoring unit is the same as the height of the foundation soil layer surface.

[0035] In the present invention, a square tube 1 is provided as the installation carrier of the monitoring unit, which is fixed along the axial direction of the single-pile foundation, ensuring that the layout of the sensors is synchronized with the structure of the single-pile foundation, and realizing the accurate and real-time monitoring of the scour depth. In each monitoring unit, the pore water pressure sensor 3 and the earth pressure sensor 4 are arranged at the same height, capable of synchronously acquiring the pore water pressure and soil stress data, and obtaining the scour depth by combining the two sets of data; the uppermost monitoring unit is at the same height as the ground soil layer surface, serving as a reference point to ensure the dynamic tracking and initial calibration of the scour depth.

[0036] A plurality of the square tubes 1 are provided; the horizontal distance between each of the plurality of square tubes 1 and the single-pile foundation 2 is 1 - 3 m. The circumferential distribution of multiple square tubes 1 can comprehensively capture the scour conditions at different positions around the single-pile foundation, especially suitable for asymmetric scour scenarios (such as the differences between the upstream side and the downstream side), improving the spatial coverage and representativeness of the monitoring data. Secondly, the horizontal distance of 1 - 3 m can not only avoid excessive interference of the square tube 1 on the flow field around the single-pile foundation 2, but also ensure that the sensors can effectively sense the soil changes caused by scour, taking into account both the measurement accuracy and engineering practicability. In addition, the data of multiple square tubes 1 can be mutually verified, and through mean processing or outlier rejection, the reliability and anti-interference ability of the monitoring results are further enhanced, providing a solid data support for the accurate judgment of the scour depth.

[0037] The length of the square tube 1 is greater than the preset maximum scour depth of the single-pile foundation 2, ensuring that the monitoring device can cover the entire possible scour range, and can provide continuous and complete monitoring data even in extreme scour cases, avoiding data loss or misjudgment caused by the scour depth exceeding the monitoring range.

[0038] The monitoring device of the present invention further includes a protective cover; the protective cover covers the outer wall of the square tube 1, and a flow guiding groove is provided on the surface of the protective cover. The protective cover can effectively protect the internal monitoring unit from the attachment of marine organisms, mechanical damage, and seawater corrosion, significantly extending the service life of the device and reducing the maintenance cost. The flow guiding groove can optimize the water flow field, reduce the impact force of the water flow on the device and the vortex interference, thereby reducing the measurement error of the sensors and improving the accuracy and stability of the monitoring data. At the same time, the flow guiding groove also helps to disperse the water flow energy, avoiding local scour damage to the device itself, and further enhancing the adaptability and reliability of the device in a complex marine environment.

[0039] The monitoring device of the present invention further includes a calibration module; the calibration module is connected to the square tube 1, and the calibration module can real-time monitor the attitude and position changes (such as inclination, displacement, etc.) of the square tube 1, and dynamically correct the sensor measurement values through data feedback, effectively eliminating the measurement deviation caused by installation errors or environmental factors (such as waves, ocean currents).

[0040] The monitoring device of the present invention has the characteristics of simple structure and reliable operation, and can efficiently monitor and analyze the scouring process. Only through multiple monitoring units can the evolution process of scouring be monitored in real time, and the scouring state of the unit can be evaluated through accurate data feedback, providing timely information support for the operation and maintenance of the unit, effectively improving the safety of the unit, ensuring the stable working state of the equipment during long-term operation, providing a strong decision-making basis for maintenance personnel, and thus realizing more efficient operation and maintenance management.

[0041] The second object of the present invention is to provide a method for real-time monitoring of the scouring depth of a monopile foundation for offshore wind power, which specifically includes the following steps: The monitoring units are sequentially numbered as the first monitoring unit, the second monitoring unit,..., the (n - 1)th monitoring unit, and the nth monitoring unit along the depth direction; When there is no scouring, the calculation formulas for the monitoring values of the pore water pressure sensor 3 along the depth direction are successively ：

[0042]

[0043] In the formula, , , , ……, are the monitoring values of the first, second, third,..., nth pore water pressure sensors 3 along the depth direction respectively; is the unit weight of water; is the height of the foundation soil layer surface from the water level; is the distance between adjacent said monitoring units; When there is no scouring, the calculation formulas for the monitoring values of the earth pressure sensor 4 along the depth direction are successively:

[0044]

[0045] In the formula, , , , ……, are the monitoring values of the first, second, third,..., nth earth pressure sensors 4 along the depth direction respectively when there is no scouring; , , ……, are the average effective unit weights of the first layer of soil, the second layer of soil,..., the (n - 1)th layer of soil respectively; is the coefficient of earth pressure at rest; The first layer of soil, the second layer of soil, ……, the (n - 1)-th layer of soil respectively refer to the soil between the first monitoring unit and the second monitoring unit, the soil between the second monitoring unit and the third monitoring unit, ……, the soil between the (n - 1)-th monitoring unit and the n-th monitoring unit.

[0046] When scouring occurs, the monitored values of the pore pressure sensor 3 and the earth pressure sensor 4 are respectively: Condition 1: 0 < < l (The scouring depth is located between the first and the second monitoring units along the depth direction)

[0047]

[0048]

[0049]

[0050] Then the scouring depth calculation formula under Condition 1 is:

[0051] Condition 2: l < < 2 l (The scouring depth is located between the second and the third monitoring units along the depth direction)

[0052]

[0053]

[0054]

[0055] Then the scouring depth calculation formula under Condition 2 is:

[0056] And so on; Condition n: (n - 1) l < Ln < n l (The scouring depth is located between the n-th group and the (n + 1)-th group of sensors along the depth direction)

[0057]

[0058]

[0059]

[0060] The formula for calculating the scour depth under working condition n is as follows:

[0061] In the formula, , , , ……, , are the monitoring values of the first, second, third, ……, nth, and (n + 1)th pore water pressure sensors 3 along the depth direction when scour occurs; In the formula, , , , ……, , , are the monitoring values of the first, second, third, ……, (n - 1)th, nth, and (n + 1)th earth pressure sensors 4 along the depth direction when scour occurs; is the average effective unit weight of the nth soil layer; The nth soil layer is the soil between the nth monitoring unit and the (n + 1)th monitoring unit; , , ……, are the corresponding scour depths under working conditions 1, 2, ……, n respectively.

[0062] This method also includes: establishing a relationship curve between the average effective unit weight of the soil and the depth in the historical monitoring data; when the scour causes changes in the soil layer distribution, updating the average effective unit weight of the soil by curve interpolation. The present invention reveals the internal law of the soil unit weight changing with depth through historical data mining, overcomes the error problem caused by soil layer reconstruction due to scour in traditional static analysis, and simplifies the parameter correction process in complex environments. Through real-time interpolation update, it can quickly respond to the dynamic changes of the soil structure and reduce the error in calculating the scour depth caused by inaccurate unit weight.

[0063] When scour occurs, if the values of the pore water pressure sensor 3 and the earth pressure sensor 4 in the same monitoring unit are equal, the scour depth is greater than or equal to the depth of the monitoring unit; when scour occurs, if the values of the pore water pressure sensor 3 and the earth pressure sensor 4 in the same monitoring unit are not equal, the scour depth is less than the depth of the monitoring unit.

[0064] Specifically, in the normal state without scour, the stress in the saturated soil is composed of effective stress and pore water pressure, that is, the total stress is equal to the sum of the effective stress and the pore water pressure. At this time, the earth pressure sensor 4 measures the total stress, while the pore water pressure sensor 3 measures the pore water pressure. Since the effective stress is always greater than zero (i.e., the soil skeleton bears part of the stress), the value of the earth pressure sensor 4 must be greater than the value of the pore water pressure sensor 3, and the two are not equal.

[0065] When scouring occurs, the water erosion gradually strips the surface soil layer, leading to changes in the soil distribution, and further affecting the stress state at the location of the monitoring unit. At this time, the relationship between the scouring depth and the depth of the monitoring unit determines the variation law of the sensor values: If the scouring depth is greater than or equal to the depth of the monitoring unit, it means that the soil at the location of the monitoring unit has been completely washed away and the original soil layer has been replaced by water. In this case, the earth pressure sensor 4 is no longer affected by the soil skeleton and only measures the hydrostatic pressure of the surrounding water. At the same time, the pore water pressure sensor 3 also measures the hydrostatic pressure, so the values of the two sensors are equal.

[0066] If the scouring depth is less than the depth of the monitoring unit, it means that the monitoring unit is still located in the non-scoured soil, and the soil skeleton still exists and bears the effective stress. At this time, the earth pressure sensor 4 measures the total stress, while the pore water pressure sensor 3 only measures the pore water pressure. Since the effective stress > 0, the value of the earth pressure sensor must be greater than the value of the pore water pressure sensor, and the two are not equal.

[0067] The present invention adopts the combination of the pore water pressure sensor 3 and the earth pressure sensor 4, which can monitor the pore water pressure and the total stress (i.e., the sum of the effective stress and the pore water pressure) at different depths in real time. Through the real-time data provided by these sensors, the pore water pressure and the earth pressure at a specific height position can be accurately obtained, and based on these data, comparison and judgment can be made, so as to calculate the scouring depth, realize the dynamic monitoring of the soil affected by scouring, timely discover potential scouring areas, and thus effectively prevent and respond to possible geological disasters or equipment failures.

[0068] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, 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 real-time monitoring device for scour depth of offshore wind power single pile foundation, characterized in that: The invention comprises a square tube (1), wherein the square tube (1) is arranged axially along a single pile foundation (2); a plurality of monitoring units are arranged on the square tube (1) at equal intervals; the monitoring units comprise a pore water pressure sensor (3) and an earth pressure sensor (4), and the pore water pressure sensor (3) and the earth pressure sensor (4) in each monitoring unit are arranged at the same height; and the horizontal height of the uppermost monitoring unit is consistent with the height of the foundation soil layer.

2. A real-time monitoring device for scour depth of offshore wind power monopile foundation according to claim 1, characterized in that: A plurality of the square tubes (1) are provided; and the horizontal distance between the plurality of the square tubes (1) and the single pile foundation (2) is 1 to 3 m.

3. The real-time monitoring device for scour depth of offshore wind power monopile foundation according to claim 1 is characterized in that: The length of the square tube (1) is greater than a preset maximum scouring depth of the single pile foundation (2).

4. The real-time monitoring device for scour depth of offshore wind power monopile foundation according to claim 1 is characterized in that: It comprises a protective cover; the protective cover is coated on the outer wall of the square tube (1).

5. A real-time monitoring device for scour depth of offshore wind power monopile foundation according to claim 4, characterized in that: The surface of the protective cover is provided with a guide groove.

6. The real-time monitoring device for scour depth of offshore wind power monopile foundation according to claim 1 is characterized in that: It comprises a calibration module; the calibration module is connected to the square tube (1).

7. A real-time monitoring method for the scouring depth of an offshore wind power single pile foundation, characterized in that: The device according to any one of claims 1 to 6 comprises the following steps: The monitoring units are numbered in sequence along the depth direction as the first monitoring unit, the second monitoring unit, ..., the n-1th monitoring unit, and the nth monitoring unit; When no scouring occurs, the calculation formula for the value monitored by the nth pore water pressure sensor (3) along the depth direction is: In the formula, is the monitoring value of the nth pore water pressure sensor (3) along the depth direction when no scouring occurs; is the specific gravity of water; It is the height of the foundation soil layer from the horizontal plane; is the distance between adjacent monitoring units; When no scouring occurs, the calculation formulas for the values ​​monitored by the soil pressure sensor (4) along the depth direction are as follows: In the formula, , , ,……, are respectively the monitoring values ​​of the first, second, third, ..., nth earth pressure sensor (4) along the depth direction when no scouring occurs; , ,……, are the average effective bulk density of the first layer of soil, the average effective bulk density of the second layer of soil, ..., the average effective bulk density of the n-1th layer of soil, respectively; is the static earth pressure coefficient; The first soil layer, the second soil layer, ..., the n-1th soil layer refer to the soil between the first monitoring unit and the second monitoring unit, the soil between the second monitoring unit and the third monitoring unit, ..., the soil between the n-1th monitoring unit and the nth monitoring unit, respectively; When scouring occurs, when (n-1) l < <n l , the calculation formula for the monitoring value of the n+1th pore water pressure sensor (3) along the depth direction is: In the formula, is the monitoring value of the n+1th pore water pressure sensor (3) along the depth direction when scouring occurs; When scouring occurs, when (n-1) l < <n l , the calculation formula for the monitoring value of the n+1th soil pressure sensor (4) along the depth direction is: In the formula, is the monitoring value of the n+1th soil pressure sensor (4) along the depth direction when scouring occurs; is the average effective bulk density of the nth layer of soil; the nth layer of soil is the soil between the nth monitoring unit and the n+1th monitoring unit; Combining the above formulas, when (n-1) l < <n l When , the scouring depth is: In the formula, The depth of scouring.

8. A real-time monitoring method for scour depth of offshore wind power monopile foundation according to claim 7, characterized in that: Also includes: Establish the relationship curve between the average effective bulk density and depth of soil in historical monitoring data; When scouring causes changes in soil layer distribution, the average effective bulk density of the soil is updated according to curve interpolation.

9. A real-time monitoring method for scour depth of offshore wind power monopile foundation according to claim 7, characterized in that: When scouring occurs, the value of the pore water pressure sensor (3) and the soil pressure sensor (4) in the same monitoring unit are equal, and the scouring depth is greater than or equal to the depth of the monitoring unit.

10. A real-time monitoring method for scour depth of offshore wind power monopile foundation according to claim 7, characterized in that: When scouring occurs, the values ​​of the pore water pressure sensor (3) and the soil pressure sensor (4) in the same monitoring unit are not equal, and the scouring depth is less than the depth of the monitoring unit.

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