| Damage of the roadbed along the river caused by the impact of mountain flood debris flow is a common geological disaster.Based on flash flood scouring and impact characteristics of fluid,such variables as the flash flood impact angle,density and different particle size of mountain torrents were selected to study the stress distribution characteristics of the impacting process by an indoor experiment simulating the impact process of a mountain flood on a retaining wall.The impact process of the mountain flood and the characteristics of debris flow are described by the experimental audio and video data.Wavelet signal denoising and spectral analysis were used to process the test data to reveal the response relationship between mountain flood impact load distribution,probability density distribution,spectral energy distribution and impact force characteristic value and mountain flood impact angle,mountain flood density and particle size under experimental conditions.The mechanical model and reliability model of mountain flood impacting gravity retaining wall stability are established and the reliability index of the retaining wall stability under experimental conditions is obtained.The main innovative results achieved are as follows:(1)This paper expounds the characteristics of mountain flood fluid flow,discusses the failure mechanism and types of highway along the river,and analyzes the process of subgrade damage caused by mountain flood scouring,impact and seepage.(2)Taking the Pingchuan debris flow gully as the prototype,a mountain torrent impact subgrade model was built for experiment,and the upper channel model set flash floods supply box,the retaining wall model with variable Angle is set at the groove mouth.camera image acquisition experiment process with high precision,DH5923 dynamic signal testing system of roadbed on time history curve of the impact of 14 points,XKVMS-02 surface flow field measurement system to collect flash flood flow velocity were collected 60 group of model experiment,obtained 756 time history curve of each time history curve contains 40000 point data.(3)The whole process of impact movement under various design conditions was recorded,the super elevation of mountain torrents in the channel and the climbing phenomenon on the subgrade panel was observed.Under the experimental conditions,the impact angle,bulk density and flow velocity of the mountain torrent show negative correlation.From the dynamic test system,the time history curve of mountain torrent impact points was extracted for the analysis of the discontinuous flow characteristics at each measuring point.As the impact Angle of mountain flood increased,the density of mountain flood decreased,and the particle size of mountain flood decreased,the array flow appeared more.(4)The wavelet de-noising principle was adopted for denoising of the impact time history curve for the analysis of statistical characteristics of the impact time history curve and the probability density of the mountain flood under the experimental circumstances.The results show that the mountain torrent impacting signal can be fitting with Gaussian distribution,and most of the coincidence degree is above 80%,and the probability density curve is in the shape of single peak,multi peak and hump.The results show that the probability density curves of different measuring points are in different shapes.The smaller the impact angle is,the more likely the probability density curve of mountain torrent impact signal will be concentrated.The peak shape of probability density curve will develop from single peak to multi peak with the increase of angle,and the height of main peak will become flat with the increase of the angle.The larger the particle size,the peak value of probability density curve will be flatter.The higher the unit density of mountain torrents is,the greater the impact force corresponding to the peak value of probability density is,the more it moving to the right,and the greater the range of impact force value is.(5)The de-noising impacting signal is decomposed and reconstructed by wavelet analysis package in MATLAB,and the mountain torrent impact energy is divided into low-frequency A8 band and high-frequency d1-d8 band by MATLAB programming.By the statistical analysis of the frequency spectrum and energy of 756 measuring points under the experimental conditions,it is found that the signal energy of each measuring point is mostly concentrated in the A8 band.At the same time,the energy distribution of impacting signal is related to the position of measuring point.the energy at the measuring point near valley is larger than that at the upper part of the channel,and the energy value of the measuring point near the valley mouth is greater than that of the measuring point far away from the valley mouth.(6)Based on the analysis of the characteristics of the flow pattern of the mountain torrent impacting the roadbed,it is concluded that the main stream of mountain torrent moves with the change of the flow rate.With the decrease of the impact angle,the thickness of the main stream and the area of the reflected water flow increase,the impact time of the debris flow on the retaining wall is different.The maximum and average value of the impact force of the test points on the roadbed panel are the measurement points at the bottom and one the left side.With the increase of the impact angle,the average value of the maximum impact force on the subgrade decreases,and the maximum and average value of the impact force on the subgrade increase with the increase of the bulk density and particle size of the mountain torrent.The distribution law of the cloud map on the mountain torrent impact contour decreases with the increase of the angle,and increases with the increase of the bulk density.With the increase of particle size,the numerical value of distribution nephogram increases.(7)A mechanical model for stability analysis of anti-sliding and anti-overturning of mountain torrent impact retaining wall is established.The reliability analysis model of sliding and overturning stability of gravity retaining wall under mountain torrent impact is established by using the central point method of the first order second moment center point method,and the necessity of reliability model for checking the stability of retaining wall is discussed.The maximum value of impact force under experimental conditions is brought into the model,and the stability model can be used to analyze the stability of gravity retaining wall.Both the reliability analysis model and the reliability analysis model show that in some of the working conditions anti sliding failure have occurred under the experimental conditions.Comparing and analyzing the results obtained by the fixed value method and the reliability index of each working condition,it is found that the value obtained by the mechanical model is relatively large,so the influence of the reliability index of the retaining wall on the stability of the retaining wall should be considered comprehensively. |
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