An online monitoring platform and method for local scour of high-capped bridge piers suitable for unidirectional water flow

Abstract

The present invention discloses an online monitoring platform for local scour of high-capped bridge piers suitable for unidirectional water flow, including a floating body, a control module, a measuring rod, a counterweight module and a rangefinder; a chamber is provided between the head and the tail of the floating body, and the tail is an open structure and is connected to the chamber; the shape of the chamber matches the cross-section of the pier, and when the floating body floats on the water surface, the tail faces and gradually approaches the pier to enclose the pier in the chamber; the measuring rod is constructed with a first horizontal sleeve, a vertical sleeve, and a second horizontal sleeve connected in sequence, one end of which is fixed to the head of the floating body, and the other end is used to connect a depth transducer; a cable for connecting the control module and the depth transducer is passed through the measuring rod. Further, the present invention also proposes a monitoring method based on the above-mentioned monitoring platform. The present invention can solve the technical problems of acoustic wave blocking of high-capped bridge piers and easy damage of electromechanical devices in a water environment.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge monitoring, and in particular relates to an online monitoring technology for local scour of high-capped bridge piers suitable for unidirectional water flow. Background Art

[0002] Bridge pier scour is one of the main causes of bridge damage due to water, and is an essential factor of concern in bridge construction and operation. Bridge pier scour generally has two main forms: bridge piers narrow the water flow, increasing the single-width flow between the bridge piers, causing scour of the entire cross-section of the river channel under the bridge, which is called general scour; bridge piers block water and change the water flow structure, and the water flow generates strong vortices around the bridge piers, causing scour within a certain range of the riverbed around the bridge piers, which is called local scour. Local scour is completed on the basis of general scour, and is the result of the combined effects of the two types of scour. It will weaken the stability of the bridge pier foundation to a certain extent, and may induce unstable phenomena such as sinking and tilting of the bridge pier due to uneven force. It will not only increase the cost of daily maintenance and reinforcement of the bridge pier foundation, but may also cause engineering quality problems or engineering accidents in serious cases.

[0003] Scour depth and shape are two typical characteristic elements of local scour of bridge piers. There are many influencing factors, which are closely related to the shape of the piers, the arrangement of the piers, the morphology of the riverbed, the intensity of the incoming flow, and the particle size of the bed sand. They are very complex. The related scour mechanisms, analysis methods, in-situ monitoring and protective treatments are all hot topics in current research. Among them, in-situ monitoring, as a basic work, can provide a relatively accurate picture of the status of pier scour, provide safety monitoring for bridge construction and operation, and accumulate data for the improvement and improvement of bridge foundation structures or protective designs. At the same time, it provides reference data for the mechanism analysis, empirical formula derivation, numerical calculation, physical model test, etc. of pier scour problems. It is of utmost importance and has become an indispensable technical means for studying pier scour. At present, in-situ observations are generally divided into two types: manual periodic observations and online real-time observations. Among manual periodic observations, ship-borne multi-beam measurements are the most popular. R2Sonic2024, Reson7125, etc. are commonly used multi-beam models. The advantage of multi-beam is that it can obtain the underwater topography around the piers more accurately. However, the disadvantage is that the instruments and equipment are expensive, the cost of a single monitoring is high, and there are certain safety risks in the operation due to the influence of passing ships. Therefore, it is difficult to update the scouring status of the piers in time, and it is impossible to form a real-time risk warning for local scouring of the piers.

[0004] Echo detection is the most commonly used technology for monitoring local scour of bridge piers. Generally, the transducer of ultrasonic, radar and other echo sounding devices is fixedly installed on the pier below the water surface. The transducer emits sound waves of a certain frequency. The sound waves propagate through the water body and reach the water-sand interface of the scour pit, and then reflect. The reflected wave is received by the transducer, and then the scour depth at the monitoring position is calculated according to the propagation speed of the sound wave and the echo time. The echo detection method has the advantages of low equipment cost, high accuracy, good operability, and convenient dynamic monitoring of the scour pit change process. However, it can only measure at a single point, and factors such as "sound wave transmission interference of complex flow around the bridge pier" and "sound wave transmission shielding of high bearing platform" will have a great impact on its measurement. Among them, the influencing factors of flow state are generally dealt with by enhancing the anti-interference ability of the transducer, adding numerical filtering, and appropriately adjusting the measuring point position of the detector (for example, whether to measure on the water surface or the back surface); "the sound wave transmission shielding of the high pier" is the key influencing factor that determines the installation method of the echo sounder. The "high pier" generally refers to a river with a large water depth. In order to facilitate construction, the top elevation of the pier is higher than the river bottom elevation, such as Figure 2 The elevation of a bridge pier on the Yangtze River shown in the figure shows that the top elevation of the pier is -7m, which is lower than the lowest water level in the history of this section of the river and has been submerged under water for many years. Figure 1 In the method of installing an echo sounder on the side wall of a pier shown in the figure, the sound wave is reflected when it encounters the abutment.

[0005] In summary, it can be seen that in the prior art, the existing monitoring platforms have not taken into account the impact of the platform shielding, the scope of use is limited, and most monitoring devices need to be installed underwater and driven by electromechanical devices. However, due to the harsh water environment, the electromechanical devices are at a very high risk of damage, resulting in poor stability of the monitoring platform. Summary of the invention

[0006] In order to solve the technical problems of acoustic wave blocking of high-cap piers and easy damage of electromechanical devices in a water environment, the present invention proposes an online monitoring platform and method for local scouring of high-cap piers suitable for unidirectional water flow. The specific technical solution includes:

[0007] Solution 1: An online monitoring platform for local scour of high-capped bridge piers suitable for unidirectional water flow, comprising a floating body, a control module, a measuring rod, a counterweight module and a rangefinder; the floating body is constructed to have a head, a tail, and a chamber located between the head and the tail and vertically connected, the tail is an open structure and communicated with the chamber; the shape of the chamber matches the cross-section of the pier, and when the floating body floats on the water surface, the tail faces and gradually approaches the pier to enclose the pier in the chamber; the measuring rod is constructed to have a first horizontal A casing, a vertical casing, and a second horizontal casing, the other end of the first horizontal casing is fixed to the head of the floating body, and the other end of the second horizontal casing is used to connect the depth transducer; a cable for connecting the control module and the depth transducer is passed through the measuring rod; the control module is arranged on the floating body, and is used to collect the data of the depth transducer and supply power to the depth transducer; the counterweight module is arranged at the tail of the floating body, and is used to ensure the overall balance of the floating body; the rangefinder is arranged on the top of the pier, and is used to measure the elevation of the top of the floating body.

[0008] As a preferred solution, the tail of the floating body is provided with at least one connecting rope for enhancing the rigidity of the floating body.

[0009] As a preferred solution, a plurality of buffer rubbers are arranged on the inner wall of the chamber.

[0010] As a preferred solution, the first horizontal sleeve, the vertical rod and the second horizontal sleeve are all formed by splicing a plurality of aluminum alloy sleeve units in pairs.

[0011] As a preferred solution, adjacent casing units are connected via threaded pipe fittings.

[0012] As a preferred solution, the first horizontal sleeve, the vertical rod and the second horizontal sleeve are all telescopic sleeves.

[0013] As a preferred solution, the counterweight module is a counterweight sandbag.

[0014] Solution 2: An online monitoring method for local scour of high-cap piers suitable for unidirectional water flow, which adopts the online monitoring platform for local scour of piers suitable for unidirectional water flow described in Solution 1, places a depth sounding transducer on the water-facing surface of the pier to be tested for testing, and uses the measuring rod to make the depth sounding transducer deviate from the high cap of the pier to ensure that the measuring sound waves of the depth sounding transducer are not affected by the side walls of the pier.

[0015] As a preferred solution, the depth sounding transducer is a HD-310 single-frequency depth sounder or a TOSDN HXF-260 single-frequency depth sounder.

[0016] Beneficial effects:

[0017] (1) The online monitoring platform for local scour of high-capped bridge piers proposed in the present invention, as a universal carrier of online monitoring equipment for bridge pier scour pits, can be conveniently equipped with depth sounders suitable for different water environments, and can solve the problem of sound wave blocking of high-capped bridge piers by adjusting the length of the measuring rod.

[0018] (2) The online monitoring platform for local scour of high-cap bridge piers proposed in the present invention does not involve complex power mechanisms, has low manufacturing costs, is convenient for equipment maintenance, and is easy to install. The maintainability of the entire system is very high. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the echo sounder's pit depth monitoring;

[0020] Figure 2 Example diagram of high-cap bridge pier structure;

[0021] Figure 3 Depth sounder installation plan;

[0022] Figure 4 Schematic diagram of steel pontoon dimensions;

[0023] Figure 5 Schematic diagram of the connection between the steel buoy and the measuring rod;

[0024] Figure 6 Schematic diagram of measuring rod connection and cable connection;

[0025] Figure 7 Schematic diagram of the installation of the depth sounding transducer: (a) Schematic diagram of the transmitting beam when installed at an angle, (b) Schematic diagram of the scattering pattern of the sound wave;

[0026] Figure 8 Schematic diagram of the depth sounder installation elevation;

[0027] Fig. 9 Schematic diagram of the planar measurement point layout of the echo sounder: (a) Schematic diagram of the measurement point layout of Pier 1, (b) Schematic diagram of the measurement point layout of Pier 2 (Pier 3 is the same as Pier 2). DETAILED DESCRIPTION

[0028] Combination Figures 2 to 8 As shown, for bridge piers with the influencing factor of "high-pedestal obstruction", Example 1 discloses an online monitoring platform for local scour of high-pedestal bridge piers suitable for unidirectional water flow (referred to as online monitoring platform), which mainly includes a steel pontoon 1, a measuring rod 2, a control cabinet 4, a counterweight sandbag 5 and a laser rangefinder 6.

[0029] like Figure 3As shown, the appearance of the steel pontoon 1 is similar to the opening part of a wrench, with an arc-shaped head and an open structure at the tail. There is a vertically penetrating chamber in the middle. The size and shape of the chamber match the bridge pier to be attached, and the bridge pier can be enclosed in the chamber. There is a certain gap between the inner wall of the chamber and the wall of the bridge pier, so that the steel pontoon 1 can float up and down with the change of water level. A plurality of buffer rubbers 7 are provided on the inner wall of the steel pontoon 1. The buffer rubbers 7 are used to isolate the pontoon 1 and the bridge pier, so that the ship and the side wall of the bridge pier are separated, which plays a role of buffering, reducing wear and protecting. A connecting rope 8 is provided at the tail of the steel pontoon 1, which is used to tighten the tail of the steel pontoon 1. On the one hand, it is used to enhance the rigidity of the steel pontoon 1, and on the other hand, it can also play a fixing role to prevent the steel pontoon 1 from floating and detaching from the bridge pier due to the influence of the water flow during the measurement process.

[0030] like Figure 4 As shown, the length of the steel pontoon 1 is 1.5L meters, the width is D+0.44+1+1 meters, and the thickness is 0.6 meters, where L represents the length of the straight section of the bridge pier along the water flow, and D represents the width of the water-facing surface of the bridge pier. The size of the buffer rubber 7 can be designed to be 40 cm long, 60 cm wide, and 20 cm thick according to the size of the steel pontoon 1, and can be hung on the inner wall of the steel pontoon 1 by ropes, or fixed to the inner wall of the steel pontoon 1 by other means, and arranged at intervals.

[0031] like Figure 5 As shown, the measuring rod 2 is fixed to the middle position of the head of the steel pontoon 1 by bolts. The measuring rod 2 is composed of a horizontal tube and a vertical tube, forming an approximately reverse "Z"-shaped structure, which is specifically composed of a horizontal tube 21, a vertical tube 22 and a horizontal tube 23 connected in series in sequence. Figure 6 As shown, for easy carrying, two horizontal tubes and one vertical tube are connected in pairs by single aluminum alloy tubes not exceeding 1m in length. Adjacent aluminum alloy tubes in the same direction can be connected by threaded pipe fittings, and aluminum alloy tubes in different directions can be connected by 90° elbow threaded pipe fittings. The free end of the horizontal tube 21 (the head end of the measuring rod 2) is fixed to the screw hole 10 at the head of the steel pontoon 1 by bolts, and the free end of the horizontal tube 23 (the end of the measuring rod 2) is connected to the depth transducer 3 by bolts. As another embodiment, the horizontal tube and the vertical tube can also be designed as a retractable structure. The length (mainly determined by the length of the horizontal tube 23) and the height (the length of the vertical tube 22) of the measuring rod 2 should be determined according to the scattering angle and the oblique installation angle of the depth transducer 3. In this embodiment, it is necessary to meet the requirement that the depth transducer 3 deviates from the bridge pier cap by at least 3m.

[0032] A cable 9 connecting the transducer 3 and the control cabinet 4 is passed through the inside of the measuring rod 2. Through the cable, the control cabinet 4 can be connected to the data of the depth transducer 3, collect the data of the depth transducer 3, and supply power to the depth transducer 3. The depth of the depth transducer 3 entering the water should generally be greater than 3m to avoid interference from surface currents or other debris, and to avoid the measuring rod 2 interfering with the safety of passage of surrounding small ships. The counterweight sandbag 5 is fixed to the tail of the steel pontoon 1, mainly to balance the center of gravity of the steel pontoon 1 to prevent it from tilting and becoming unstable after the measuring rod 2 is installed. The laser rangefinder 6 is installed on the pier to measure the elevation of the top of the steel pontoon 1, so as to further calculate the elevation of the bottom of the pier scour pit.

[0033] When testing is required, the equipped steel pontoon 1 can be transported to the measurement site by tugboat or other equipment and inserted into the bridge pier. In order to avoid interference from the side walls of the bridge pier, the sound waves at the river bottom should deviate from the wall by a certain safe distance. For a transducer with a scattering angle of about 8°, when the transducer is 50m away from the riverbed, the scattering radius is 6.96m. Figure 7 As shown in the figure, when the inclined installation angle is 5°, the calculated deviation distance is 4.37m, and the sound wave will definitely directly touch the side wall of the pier. Figure 8 , the transducer deviates from the pier cap position by 3m, 3+4.37=7.37m, which is larger than the scattering radius of 6.96m, to avoid the influence of the pier side wall. Table 1 gives the corresponding deviation distances when the transducer is at different depths from the riverbed, and the appropriate position of the transducer deviating from the pier cap can be obtained accordingly.

[0034] Table 1 Transducer scattering angle and deviation distance calculation

[0035] Transducer distance to riverbed (m) Scattering angle (°) Scattering radius (m) Slant angle (°) Deviation distance (m) 10 8 1.39 5 0.87 20 8 2.78 5 1.75 30 8 4.18 5 2.62 40 8 5.57 5 3.50 50 8 6.96 5 4.37

[0036] Furthermore, the elevation of the bottom of the pier scour pit can be calculated by using the water depth measured by the depth sounder and the elevation of the top of the steel pontoon measured by the laser rangefinder. The specific calculation formula is as follows:

[0037] The elevation of the bottom of the pier scour pit = the elevation of the top of the steel pontoon - the vertical distance between the transducer sound wave emitting surface and the top of the steel pontoon - the water depth measured by the transducer * COS (tilt angle).

[0038] The calculated elevation value of the bottom of the pier scour pit is used as the result of online monitoring of local scour of the pier and is a key parameter for measuring the severity of scour. It can be seen that the online monitoring of local scour of piers with high caps can be realized through this platform.

[0039] Further, for the online monitoring platform for local scour of high-cap bridge piers suitable for unidirectional water flow described in Example 1, Example 2 discloses a preferred case of a depth sounder and explains the reasons for installing the depth sounder on the water-facing surface of the online monitoring platform, including:

[0040] Combination Fig. 9 As shown in the figure, the bridge piers selected for the test are numbered 1, 2 and 3, and the measurement point locations are as follows: Fig. 9 (a) and Fig. 9 (b) The test equipment is fixedly installed on the side of a motor vessel, including SDE-18S single-frequency depth sounder, ATLAS DESO 35 dual-frequency depth sounder, HD-310 single-frequency depth sounder, TOSDN HXF-260 single-frequency depth sounder and other related instruments; the transducers are all placed 50cm below the water surface; the measurement results are compared with the R2Sonic2024 multi-beam results, showing:

[0041] a) During the measurement of Pier 1, the depth from the water surface to the bottom of the pit was less than 6m. The flow velocity measurement results of Sontek Flowtracker ADV showed that the surface velocity of the flow around Pier 1 was about 0.2m / s, and the flow pattern was relatively stable. All types of equipment were less affected by the interference of the pier wall and the flow pattern. Whether the transducer beam was emitted vertically downward or tilted downward at a certain angle (≤15°) away from the pier wall, Figure 7 ) launch, all have good test results, even if it is installed close to the pier wall (measurement point 2), relatively ideal data can be obtained.

[0042] b) During the measurement of Pier 2, the water depth from the water surface to the bottom of the pit was 34 to 39 meters. The flow velocity of Pier 2 was relatively large, and the flow velocity around the pier on both sides was about 1.3 m / s. At this time, the best installation position for the depth sounder was point 6 on the water-facing surface of the pier. Even if the transmission was tilted at 5°, although there was occasional clutter interference, by defining the depth sounding threshold and filtering the echo data, an ideal result close to that of multi-beam could be obtained.

[0043] c) For Pier 3, the water depth of the scouring pit during the measurement period generally exceeded 50m, and the flow velocity on the surface of the flow around the pier on both sides was about 2m / s, which was the main risk position for scouring of the bridge pier. The test results showed that Point 6 on the water-facing surface of the pier was still the best installation position for the depth sounder.

[0044] d) Among several types of depth sounding equipment, the HD-310 single-frequency depth sounder and the TOSDN HXF-260 single-frequency depth sounder both have a strong ability to capture strong bottom echoes, and the measurement results are similar to those of multi-beam actual measurements.

[0045] In summary, it can be seen that the online monitoring platform for local scour of high-support bridge piers suitable for unidirectional water flow described in the present invention has a suitable single-frequency depth sounder that can be carried. The depth sounding transducer is also suitable when arranged on the water-facing side of the monitoring platform because the interference from the flow around the piers is small. In addition, since the scour pits of the bridge piers generally have the general rule that the water-facing side is deep and the water-retaining side is shallow, the depth sounding transducer is also suitable for installation on the water-facing side of the monitoring platform.

[0046] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An online monitoring platform for local scour of high-capped bridge piers suitable for unidirectional water flow, characterized in that: The invention comprises a floating body, a control module, a measuring rod, a counterweight module and a rangefinder; the floating body is constructed to have a head, a tail and a chamber located between the head and the tail and penetrating in the vertical direction, the tail being an open structure and communicating with the chamber; the shape of the chamber matches the cross section of the pier, and when the floating body floats on the water surface, the tail faces and gradually approaches the pier to enclose the pier in the chamber; the measuring rod is constructed to have a first horizontal casing, a vertical casing and a second horizontal casing connected in sequence, the other end of the first horizontal casing is fixed to the head of the floating body, and the other end of the second horizontal casing is used to connect a depth transducer; a cable for connecting the control module and the depth transducer is passed through the measuring rod; the control module is arranged on the floating body to collect data of the depth transducer and to supply power to the depth transducer; the counterweight module is arranged at the tail of the floating body to ensure the overall balance of the floating body; the rangefinder is arranged at the top of the pier to measure the elevation of the top of the floating body.

2. The online monitoring platform for local scour of high-cap bridge piers as claimed in claim 1 is characterized in that: The tail of the floating body is provided with at least one connecting rope for enhancing the rigidity of the floating body.

3. The local scour online monitoring platform for high-cap bridge piers according to claim 1 is characterized in that: The inner wall of the chamber is arranged with a plurality of buffer rubbers.

4. The online monitoring platform for local scour of high-cap bridge piers as claimed in claim 1, characterized in that: The first horizontal sleeve, the vertical rod and the second horizontal sleeve are all formed by splicing a plurality of aluminum alloy sleeve units in pairs.

5. The online monitoring platform for local scour of high-cap bridge piers as claimed in claim 4, characterized in that: Adjacent casing units are connected by threaded pipe fittings.

6. The local scour online monitoring platform for high-cap bridge piers according to claim 1 is characterized in that: The first horizontal sleeve, the vertical rod and the second horizontal sleeve are all telescopic sleeves.

7. In the online monitoring platform for local scour of high-cap bridge piers as described in claim 1, the counterweight module is a counterweight sandbag.

8. An online monitoring method for local scour of high-cap bridge piers suitable for unidirectional water flow, characterized in that: By using the local scour online monitoring platform for high-cap piers suitable for unidirectional water flow as described in any one of claims 1 to 7, a depth sounding transducer is placed on the water-facing surface of the pier to be tested for testing, and the depth sounding transducer is deviated from the high cap of the pier by the measuring rod to ensure that the measuring sound waves of the depth sounding transducer are not affected by the side walls of the pier.

9. The online monitoring method for local scour of high-cap bridge piers suitable for unidirectional water flow as claimed in claim 8, characterized in that: The depth sounding transducer is selected from HD-310 single-frequency depth sounder or TOSDN HXF-260 single-frequency depth sounder.

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