CN206396814U - A kind of novel bridge pile foundation is under water by flushing monitoring device - Google Patents

Abstract

A kind of novel bridge pile foundation is under water by flushing monitoring device, including test tube under water, measurement assembly and data collecting instrument, the test tube under water is located at pile foundation side to be monitored, the measurement assembly is located at the surface side that meets water of the test tube under water, the measurement assembly includes load measurement column and soil pressure force cell, the soil pressure force cell is located in the load measurement column, the load measurement column is equidistantly spaced from the test tube under water from top to bottom, and the signal output part of the soil pressure force cell is connected with the data collecting instrument.A kind of easy to operate, precision of the utility model offer is higher, real-time is good, effectively realize the novel bridge pile foundation remotely monitored under water by flushing monitoring device.

Description

A new type of underwater scouring monitoring device for bridge pile foundations

technical field

The invention relates to the safety monitoring of the substructure of a cross-sea and river-crossing bridge project, in particular to a quantitative and real-time scour monitoring device for bridge pile foundations in water.

Background technique

The substructure of the bridge supports the entire superstructure and vehicle load through the underwater pile foundation. The underwater pile foundation bears the vertical load of all bridge structures. The change of the soil pressure on the side of the pile directly determines the bearing capacity of the pile foundation. However, the underwater pile foundations of cross-sea and river-crossing bridges are affected by water erosion, and changes in pile side soil erosion and silting will occur, which has a great impact on the safety of bridge pile foundations, and even cause bridge collapse and damage. In recent years, such accidents at home and abroad have occurred. happens sometimes. Therefore, the observation of the underwater foundation soil layer near the pile foundation in bridge engineering has become a very relevant problem in the engineering field in recent years. Bridge damage and damage caused by water erosion is also a problem that needs to be paid attention to in bridge structural health monitoring, which is of great significance to ensure the long-term safe operation of cross-sea and river bridges. If the real-time information on the change of the soil layer on the side of the bridge pile foundation is eroded by the water flow, the appropriate engineering reinforcement method can be adopted in the bridge operation process to effectively reduce the probability of accidents and prolong the service life of the structure.

For the monitoring of the erosion of the underwater soil layer near the bridge pile foundation, the current existing methods are through fixed instrument monitoring and portable instrument monitoring, and the principles adopted include sonar technology and multi-beam methods. The basic principle of the existing pile foundation scour test method is mainly to measure the depth change between the water surface and the medium of the sediment layer. Generally speaking, these methods still have shortcomings: First, these methods generally cannot be tested continuously in real time, and usually need to go out of the ship for observation regularly. And it cannot really consider the real change of soil pressure on the side of the pile caused by the complex reciprocating changes of the scour-silt layer. The test only obtains the depth change of the water-sediment interface, and cannot consider the density change of the sediment layer below the interface. Therefore, it is impossible to accurately obtain whether the lateral soil pressure of the pile foundation has changed. The accuracy of general measurement is also very susceptible to interference from external environments such as waves, and needs to be constantly corrected to adapt to environmental changes in different waters. Second, this method cannot monitor the changes in earth pressure caused by scour near the bridge pile foundation, and what is obtained is the evolution of large-scale underwater terrain scour, and the pile side is the blind spot of the test instead.

Contents of the invention

In order to overcome the shortcomings of the existing monitoring of the erosion of the underwater soil layer near the pile foundation, such as complex operation, low precision, poor real-time performance, and inability to realize remote monitoring, the present invention provides a simple and convenient operation, high precision, and good real-time performance. A new bridge pile foundation underwater scour monitoring device that effectively realizes remote monitoring.

The technical solution adopted by the present invention to solve its technical problems is:

A novel bridge pile foundation underwater scour monitoring device, comprising an underwater measuring tube, a measuring assembly and a data acquisition instrument, the underwater measuring tube is located at the side of the pile foundation to be monitored, the measuring assembly is located at the underwater measuring On the upstream side of the pipe, the measurement assembly includes a force measuring column and an earth pressure load cell, the earth pressure load cell is located in the force measuring column, and the force measuring columns are arranged at equal intervals from top to bottom. On the underwater measuring pipe, the signal output ends of the earth pressure load cell are all connected to the data acquisition instrument.

Further, the earth pressure load cell includes a dowel rod for sensing earth pressure and an optical fiber grating sensor for sensing the earth pressure transmitted by the dowel rod, and the dowel rod cooperates with the optical fiber grating sensor.

Still further, the force-measuring column is arranged radially, the dowel rod is located in the inner cavity of the force-measuring column, and the fiber grating sensor is located at the bottom of the force-measuring column.

The monitoring device also includes a data transmitting device, and the data acquisition instrument is connected with the data transmitting device.

The technical concept of the present invention is: optical fiber is one of the most widely used sensitive components in the research of intelligent material systems at present, and its working principle is that the change of external physical quantity causes the change of the central wavelength of the optical fiber, and the measured value. This measurement method has clear thinking and convenient operation, and is easily accepted by the majority of engineering and technical personnel. The advantages of optical fiber sensing components are mainly anti-electromagnetic interference; corrosion resistance; quasi-distributed measurement, absolute measurement, small signal attenuation; high sensitivity and high precision. In addition, in recent years, the real-time safety monitoring of structures has become one of the research hotspots at home and abroad, and the optical fiber technology, which is an important means of structural health monitoring, has also been greatly developed. Therefore, this device combines the advantages of fiber grating for sensing and transmission, and specifically develops a fiber grating sensor suitable for underwater bridge pile foundation monitoring and a systematic real-time monitoring device for data transmission and analysis, giving full play to the accuracy of fiber grating monitoring. It has the characteristics of high performance and good durability, overcomes the shortcomings of traditional testing methods, and is very suitable for scour monitoring of new and existing underwater bridge pile foundations, and has unique advantages.

This scheme monitors the change of pile side soil pressure at different depths near the pile foundation and the whole process of scour in real time, so as to obtain the impact of scour depth on the force of the pile foundation, and analyze the aperiodicity of pile side soil pressure under wave and current scour. The stress state between the pile and the soil and the safety margin of scour can be obtained in real time. This can not only eliminate the impact of the reciprocating change of the underwater silt layer on judging the scour safety of the pile foundation, but also be more accurate and simple. The monitoring device can be installed at one time to realize remote real-time monitoring.

The beneficial effects of the invention are mainly manifested in: simple and convenient operation, high precision, good real-time performance, and effective realization of remote monitoring.

Description of drawings

Figure 1 is a cross-sectional view of the underwater measuring tube.

Figure 2 is a top view of the underwater measuring tube.

Figure 3 is a schematic diagram of the working principle of the underwater measuring tube.

Fig. 4 is a schematic diagram of force on the dowel bar of the underwater measuring tube.

Fig. 5 is a graph of pressure variation.

Fig. 6 is a flowchart of the detection device.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings.

Referring to Figures 1 to 6, a new type of monitoring device for underwater scouring of bridge pile foundations, the monitoring device includes an underwater measuring tube 2, a measuring component and a data acquisition instrument 1, and the underwater measuring tube 2 is located at the pile to be monitored The base side, the measurement assembly is located on the upstream side of the underwater measuring tube, the measurement assembly includes a load cell 3 and an earth pressure load cell 4, and the earth pressure load cell 4 is located on the load cell In the column 3 , the force measuring columns 3 are arranged at equal intervals from top to bottom on the underwater measuring tube 2 , and the signal output ends of the earth pressure load cells 4 are all connected to the data acquisition instrument 1 .

Further, the earth pressure load cell 4 includes a dowel bar 41 for sensing earth pressure and a fiber optic grating sensor 42 for sensing the earth pressure transmitted by the dowel bar 41, the dowel bar 41 and the fiber grating Sensor 42 fits.

Still further, the force measuring column 3 is radially arranged, the force transmission rod 41 is located in the inner cavity of the force measuring column 3 , and the fiber grating sensor 42 is located at the bottom of the force measuring column 3 .

The monitoring device also includes a data transmitting device 5 , and the data acquisition instrument 1 is connected to the data transmitting device 5 .

As shown in Figure 4, the underwater measuring tube is driven into the soil layer, so that the change of external earth pressure can be transmitted to the position of the force measuring column 3, and the soil at each dowel bar position is measured according to the optical fiber on the force measuring column. The pressure value, the external wave flow erosion will change the earth pressure on the earth pressure load cell, and the fiber Bragg grating senses the difference in strain. From this strain value, the degree of erosion can be known, and the measured Data is transmitted remotely to a computer for analysis.

According to design requirements, the sensor is arranged in the soil layer near the pile foundation of the cross-sea and river bridge, so that the earth pressure force sensor is in contact with the soil. When the soil on the side of the pile is washed by the water flow, the elastic structure in the soil pressure load cell is deformed, which causes the wavelength of the fiber grating embedded in the elastic structure to change, and the signal measured by the load cell is transmitted through the data transmission line composed of parallel optical fibers. To the data acquisition instrument installed on the top of the underwater measuring pipe, and then through signal analysis and mechanical analysis, real-time changes in underwater scour depth and lateral soil pressure of pile foundations can be obtained.

The measuring element is composed of optical fiber, elastic material and earth pressure load cell. The spacing of the earth pressure load cell can be determined according to the actual demand accuracy; the lead-out line of the fiber grating can lead out the data line through the open-hole sleeve hose.

The technical principle and theoretical basis of the fiber grating sensor:

λ _B = 2nΛ

In the formula, n is the effective refractive index of the core mode, and Λ is the optical grating period. When the temperature, stress, strain or other physical quantities of the optical grating change, the period of the grating or the refractive index of the fiber core will change, so that the wavelength of the reflected light will change. By measuring the change of the reflected wavelength before and after the physical quantity changes, the The change of the physical quantity to be measured can be obtained. The drift due to changes in temperature, stress and strain can be expressed as:

In the formula, ε is the applied strain, v is Poisson's ratio, P _ij is the Pockels voltage coefficient of the photoelastic tensor, α is the thermal expansion coefficient of the fiber material, and ΔT is the temperature change.

According to the formula of mechanics of materials,

F＝σ·A

In the formula, σ is the earth pressure, and A is the surface area of the earth pressure sensor.

As shown in Figure 5, n soil pressure load cells are measured through the underwater measuring tube, and the pressure values at n different points are measured to draw the pressure change curve as shown in the figure below. The first half of the sudden change position Pi of the pressure change curve is water The pressure value curve is the pressure value curve of earth pressure after a sudden change, from which the water depth and scour depth can be known.

α structure health monitoring has become one of the hot issues in the world research, and as one of its most promising sensitive components, optical fiber has also been greatly developed. At present, optical fiber sensors have been widely used in civil engineering, aerospace, petrochemical, medical, In environmental engineering and other fields, building an all-fiber health monitoring system has become one of the development goals of structural health monitoring in the future. Optical fiber-based sensor is a kind of sensing probe of optical fiber monitoring system. It is a functional sensor with optical fiber as the sensitive element. In structures such as civil engineering and water conservancy, by changing the structural size and packaging form of the sensor, the range or accuracy can be easily changed, the reliability is good, the ability to resist electromagnetic interference is strong, and it is easy to form a sensor network and easy to install and arrange. The collection and storage of data can be based on the Alibaba Cloud platform, which can accommodate massive amounts of data, and the number of servers can be expanded elastically.

In this embodiment, the fiber Bragg grating is embedded in the elastic structure, and then the elastic structure and the fiber Bragg grating are put into the soil pressure load cell to form a fiber Bragg grating-based scour sensor that can monitor changes in the thickness of the external soil layer. The optical fiber is combined with the elastic structure and put into the earth pressure load cell. Since the earth pressure load cell is sealed and the material with high corrosion resistance is used, the measurement part has high durability, so the patent's The washout sensor has higher durability in wet environments. The sensor has the advantages of corrosion resistance, high sensing accuracy, anti-electromagnetic interference, quasi-distributed monitoring, absolute measurement of physical quantities, and the like. Finally, this fiber optic scour sensor is suitable for the actual engineering needs of long-term monitoring, and sensors with different precision and different ranges can be designed according to engineering needs. The optical fiber grating scouring sensor can effectively monitor the scouring degree of the soil on the side of the pile of the cross-sea and river bridge, and can play an early warning function when the soil on the side of the pile is excessively lost under the action of flood scouring. The sensitive element of the device is optical fiber grating, and the force transmission mechanism adopts dowel rods and internal elastic materials. It is cleverly designed and simple in structure. It solves the problem of foundation soil erosion of large-scale civil engineering and water conservancy structures, and has great practical application significance.

Claims (4)

1. a kind of novel bridge pile foundation is under water by flushing monitoring device, it is characterised in that：The monitoring device includes surveying under water Pipe, measurement assembly and data collecting instrument, the test tube under water are located at pile foundation side to be monitored, and the measurement assembly is located at the water The surface side that meets water of lower test tube, the measurement assembly includes load measurement column and soil pressure force cell, the soil pressure force-measuring sensing Device is located in the load measurement column, and the load measurement column is equidistantly spaced from the test tube under water from top to bottom, and the soil pressure is surveyed The signal output part of force snesor is connected with the data collecting instrument.

2. novel bridge pile foundation as claimed in claim 1 is under water by flushing monitoring device, it is characterised in that：The soil pressure Force cell includes the transmission rod to sense soil pressure and the fiber grating of the soil pressure for perceiving transmission rod conduction is passed Sensor, the transmission rod coordinates with the fiber-optic grating sensor.

3. novel bridge pile foundation as claimed in claim 2 is under water by flushing monitoring device, it is characterised in that：The load measurement column Radially arrange, the transmission rod is located at the inner chamber of the load measurement column, the fiber-optic grating sensor is located at the load measurement column Bottom.

4. the novel bridge pile foundation as described in one of claims 1 to 3 is under water by flushing monitoring device, it is characterised in that：Institute Stating monitoring device also includes data sending apparatus, and the data collecting instrument is connected with the data sending apparatus.