Patent ID: 11859365
Assignee: ZHEJIANG UNIVERSITY OF TECHNOLOGY
Field: Civil engineering (Other fields)
Classification: CPC E  H | IPC E  H

Claim 7:
8. A monitoring method of the system for bridge scour multi-source monitoring according to claim 2, comprising the following steps:
1) under an ordinary weather environment:
1.1) installing the seepage pressure sensor on the pile surface at the stainless hoop, wherein the seepage pressure sensor operates in real time, data are uploaded to the data industrial personal computer through wires, the data industrial personal computer obtains real-time tidal level data through a preset algorithm, then controls turning on and off of the single beam echo sounder in accordance with whether or not the real-time tidal level data reach a set monitoring threshold, and sets a wave velocity in accordance with the propagation velocity of sound wave in an actual marine environment, so as to avoid affecting monitoring accuracy by systematic error caused by complicated and volatile external environment and long-time operation of the single beam echo sounder, and monitoring data of the single beam echo sounder shows the depth change of a scour interface at a bridge pile foundation measuring point;
setting an acquisition threshold h′ of the single beam echo sounder, wherein the data industrial personal computer automatically controls the turning on and off of the single beam echo sounder through a tidal level elevation obtained by conversion of the seepage pressure sensor that is installed on the pile surface at the stainless hoop, a sounding sampling is carried out when the tidal level is greater than h′, and the sounding sampling is stopped when the tidal level is less than h′, so as to avoid affecting monitoring accuracy by accumulation of measuring error caused by long-time operation of the single beam echo sounder; in order to prevent the contingency of single data, when a considerable amount of measuring data reach h′, turning on and off of the single beam echo sounder is automatically controlled; measuring data htr of depths from a bottom surface of the transducer of the single beam echo sounder to a water bottom shows a change of a soil layer interface of an upstream side of the pile, and then the change Δhtr of a scour depth is obtained based on the difference of the depths, that are measured at different time, from the bottom surface of the transducer of the single beam echo sounder to the water bottom; and relevant calculation theory thereof is as follows:, h
      1
    
    =
    
      
        
          P
          k
        
        /
        
          γ
          1
        
      
      -
      
        h
        2
      
    
  

  
    
      h
      tr
    
    =
    
      
        1
        2
      
      ⁢
      Ct
    
  

wherein h1 is the tidal level elevation; Pk is an actual measured data of the seepage pressure sensor on the pile surface at the stainless hoop; γ1 is the volume weight of seawater; h2 is a distance from the seepage pressure sensor on the pile surface at the stainless hoop to a datum plane of the tidal level; htr is a distance from a bottom of the transducer of the single beam echo sounder to a seabed surface; C is an actual average sound velocity of the seawater; and t is two-way time of the sound waves;
1.2) setting an amplitude of change of depths of the single beam echo sounder, wherein when sounding data reaches the amplitude of change, the data industrial personal computer carries out automatic control to turn on the high-frequency real-time bridge dynamic characteristic monitoring system and the scoured seabed soil pressure change testing system to make the three subsystems operate normally, so as to obtain clock-synchronous real-time monitoring data of the three subsystems;
setting sampling frequencies of the pressure sensor and the seepage pressure sensor in the scoured seabed soil pressure change testing system, and averaging the pressure data P2 and P3 thereof, wherein data acquired by the pressure sensor includes soil layer pressure values and water pressure values, and data acquired by the seepage pressure sensor only includes water pressure values, namely, a silt scour or back-silting pressure value ΔP is reflected by a value difference between the pressure sensor and the seepage pressure sensor; and the seabed soil effective unit weight γ2 is measured by carrying out drilling sampling on a seabed bearing stratum, namely, a silt scour or back-silting thickness h3 on a lateral pile soil pressure monitoring system is obtained;, P
        2
      
      =
      
        
          1
          n
        
        ⁢
        
          
            ∑
            
              i
              =
              1
            
            n
          
          ⁢
          
            P
            i
          
        
      
    
    ,
    
      
        P
        3
      
      =
      
        
          1
          n
        
        ⁢
        
          
            ∑
            
              j
              =
              1
            
            n
          
          ⁢
          
            P
            j
          
        
      
    
  

  
    
      Δ
      ⁢
      P
    
    =
    
      
        P
        2
      
      -
      
        P
        3
      
    
  

  
    
      h
      3
    
    =
    
      
        Δ
        ⁢
        P
      
      
        γ
        2
      
    
  

wherein Pi is an actual measured data of the pressure sensor in the scoured seabed soil pressure change testing system, i is actual measured data points of the pressure sensor at different time, n is a number of data, Pj is an actual measured data of the seepage pressure sensor in the scoured seabed soil pressure change testing system, and j is actual measured data points of the seepage pressure sensor at different time;
when an interface of the seabed bearing stratum changes, judging whether or not an absolute position of a system device changes by further analyzing the scoured seabed soil pressure change testing system and the seepage pressure sensor on the pile surface at the stainless hoop, and then comprehensively judging a change of a scour depth by considering the silt scour or back-silting situation;, P
      1
    
    =
    
      
        1
        n
      
      ⁢
      
        
          ∑
          
            k
            =
            1
          
          n
        
        ⁢
        
          
        
        ⁢
        
          P
          k
        
      
    
  

  
    
      h
      4
    
    =
    
      
        (
        
          
            P
            3
          
          -
          
            P
            1
          
        
        )
      
      ⁢
      
        /
      
      ⁢
      
        γ
        1
      
    
  

wherein h4 is a depth from the scoured seabed soil pressure change testing system to the seepage pressure sensor on the pile surface at the stainless hoop; Pk is an actual measured data of the seepage pressure sensor on the pile surface at the stainless hoop, n is a number of data points, and k is actual measured data points of the seepage pressure sensor on the pile surface at the stainless hoop at different time; and P1 is an average value of seepage pressures monitored by the seepage pressure sensor on the pile surface at the stainless hoop;
1.3) carrying out high-frequency dynamic monitoring on acceleration data of the pile top and the pile cap as well as dynamic strain data of the top and bottom of the pile by the high-frequency real-time bridge dynamic characteristic monitoring system, acquiring acceleration signals under action of earth pulsation, and carrying out spectral analysis on the signals to obtain structural natural vibration frequency information contained in response signals; carrying out modeling and grid dividing on a bridge model based on ANSYS finite element software, and simulating pile-soil interaction by setting spring units in the ANSYS finite element software, wherein the spring stiffness K is determined by an m method, and a value model is modified by combining a scour depth obtained by manual underwater exploration in an installation day with the actual measured acceleration data for the installation day to establish a benchmark numerical model; stimulating different scour depths of the bridge with the benchmark numerical model by deleting spring units at different depths to obtain natural vibration frequencies under different scour depth working conditions; carrying out manual neural network training on partial natural vibration frequency results and corresponding scour depths obtained through stimulation, and carrying out checking with the rest of the natural vibration frequency results to ensure the accuracy of a network model, wherein the grid model selects a natural vibration frequency sensitive order as a network input parameter, and an output parameter is the scour depth; inputting corresponding natural vibration frequencies identified by the actual measured acceleration data of the pile top and the pile cap into the manual neural network, thereby obtaining bridge scour depth values; and conversing the dynamic strain data into dynamic deflection data of the pile to evaluate bridge operation safety statuses by adopting a strain-curvature-deflection relationship through a curvature function-based method;
2) under a rugged environment:
2.1) carrying out control to simultaneously turn on the three subsystems of the intelligent monitoring system by the data industrial personal computer to realize dynamic online operation of the three subsystems so as to obtain clock-synchronous real-time monitoring data of the three subsystems, obtaining sounding data of the single beam echo sounder in the adjustable sound velocity underwater depth monitoring system according to the step 1.1), obtaining pressure and seepage pressure data in the scoured seabed soil pressure change testing system according to the step 1.2), and obtaining acceleration data and dynamic strain data according to the high-frequency real-time bridge dynamic characteristic monitoring system in the step 1.3), thereby obtaining scour depths through respective conversion of the high-frequency real-time bridge dynamic characteristic monitoring system, the adjustable sound velocity underwater depth monitoring system and the scoured seabed soil pressure change testing system.