| The soil-rock mixture is a kind of special engineering geological material with strong inhomogeneity,discontinuity and nonlinearity.Soil-rock mixture macroscopic mechanical properties and the content of stone,such as size,shape,micro-structure features are closely related,in-depth study of soil-rock mixture's micro-structure and structural evaluation method for the engineering application of soil-rock mixture has important theoretical significance and practical value,Existing studies have shown that the wave propagation characteristics of soil-rock mixture are very sensitive to the stone content and density.In view of this,starting from the acquisition of the micro-structure characteristics of soil-rock mixtures,this paper adopts the PFC discrete element particle flow numerical simulation technology to establish the micro-structure model of soil-rock mixtures,studies the wave and electrical propagation characteristics of soil-rock mixtures,and analyzes the influence of the micro-structure characteristics of soil-rock mixtures on the wave propagation characteristics.The main research contents and results are as follows:(1)Through the main micro-structure characteristic parameters of soil-rock aggregate analysis and quantitative description,select stone content feature size and shape of stone,stone the three parameters,particle flow code(PFC)technology,based on discrete element according to different shape stone,stone is established template(clump template),during building model can be directly call stone template from the template library.Finally,the numerical model of soil-rock mixture with different micro-structure parameters is established.(2)Based on PFC software,the wave propagation process of soil-rock mixture was numerically simulated and analyzed,and the source and boundary conditions affecting the wave field characteristics of soil-rock mixture were studied.The excitation mode of wave analysis and the appropriate boundary conditions were determined,and the distribution of signal collection and measurement points was determined.The history was used to sample and store the velocity field and displacement field of the model,and finally the waveforms under different micro-structure characteristics were obtained.(3)Based on the waveform obtained by numerical simulation,the influence of different micro-structure parameters on time-domain fluctuation parameters was analyzed.The take-off time decreases accordingly;With the increase of the characteristic size of the rock,the amplitude of the first wave gradually decreases,and the take-off time gradually increases.The peak values of velocity wave of the three types of rock and soil mixture are as follows: the circle is the largest,the square is the second,and the rectangle is the smallest.Take off time: circle smallest,square second,rectangle largest trend.(4)The wave signal was processed by using the method of Fourier transform and wavelet analysis,and the relationship between the frequency domain parameters of the wave propagation of soil-rock mixture and the micro-structure parameters was analyzed.The results showed that: with the increase of the rock-bearing ratio,the maximum amplitude,main frequency and weighted spectral area of the frequency domain gradually increased.With the increase of the characteristic size,the maximum amplitude,the main frequency and the weighted spectral area in the frequency domain gradually decrease.The maximum amplitude and weighted spectral area in the frequency domain waveform are not obvious due to the different shapes of the rock.But the main frequency has the square biggest,the rectangle second,the circle smallest obvious trend.(5)Based on the wave test of soil-rock mixture samples,the correlation between the rock-bearing rate and time-frequency parameters of wave propagation was obtained through processing and analyzing the collected signals,which verified the feasibility of numerical simulation analysis. |
PDF Full Text Request