Study On Measuring The Length Of Bridge Foundation Pile By Cylinder Dynamic Measurement

In this thesis,based on the special engineering background of detecting the length of bridge foundation pile,the detection of bridge foundation pile length has the difficulties of narrow detection surface,difficult operation on site and pile top being covered.In order to avoid these difficulties,the cylindrical dynamic measurement method is selected,and the method of laboratory test and numerical simulation is adopted to carry out technical research on the cylindrical dynamic measurement method to detect the length of bridge foundation pile.Then,the technical research results are applied to detect the length of foundation pile of a bridge in Xuzhou,and the final solution is obtained.In this thesis,the basic theory of stress wave,basic principle of cylindrical dynamic measurement method and wavelet analysis method for detecting deep reflection signal of pile bottom are deeply explored,and the theoretical basis of cylindrical dynamic measurement method for detecting the length of foundation pile is basically constructed.Then COMSOL Multiphysics software was used to simulate the single pile model and the platform pile model respectively by using cylindrical dynamic measurement method to measure the pile.At the same time,based on the single pile model,the vibration was excited at two different positions of the pile top and pile side.It was concluded that it was difficult to solve the stress wave velocity by using the dual velocity method in the cylindrical dynamic measurement method.The wave velocity can be solved by the radial reflected wave.By comparing the signals of single pile model and table-pile model,it is found that the superstructure will make the waveform more chaotic,but the waveform changes of the two models are similar in general.When the pile top is excited,the signal waveform collected from the pile side and the pile top can intuitively identify the reflected wave arrival time of the pile bottom,but when the pile side is excited,only the signal waveform collected from the pile top can identify the reflected wave arrival time of the pile bottom,but the signal waveform of the pile side is difficult to identify.Finally,through the observation of the wave field snapshot,it is found that the knocking energy propagates in the form of wave wave in the foundation pile with the knock cross section as the boundary,which can be summarized into three typical propagation modes.One is the propagation to the top of the pile through the reflection of the pile top and then to the bottom of the pile,and some of the energy is reflected back and forth between the knock point and the boundary.Then,the feasibility of cylinder dynamic measurement method to detect the length of model pile was verified through the laboratory similarity test,and the detection operating system suitable for field detection of foundation pile length by cylinder dynamic measurement method was established,and the optimal signal receiving position was obtained.Finally,the column dynamic measurement method is used to detect the length of a Xuzhou bridge foundation pile.The radial reflection wave is used to measure the stress wave velocity of the foundation pile.The signal obtained from the numerical simulation results is decomposed based on Db6 wavelet function,which verifies that the wavelet analysis method can effectively pick up the deep reflected wave of the pile bottom.Then,Db6 wavelet function is used to decompose the field measured signal by7 levels of multi-scale,and the pile length is solved by picking up the reflected wave time of pile bottom.