Experimental Research Of Digital Surface Wave Instrument In Weak Layer Detection

With the rapid growth of national economy,China's road infrastructure has also developed rapidly.The project construction has higher and higher requirements for the quality of the preliminary design survey and construction process.In the western region of China,especially in the southwest region,due to the special natural geography and geological environment,the geological structure is complex and the geological defects under the highway come into being,which often causes amount of geological disasters.Unknown geological disasters cause a lot of threat to construction and safe management of road projects.At present,the accuracy rate,speed and convenience of NDT equipment can not satisfy the requirements of engineering exploration.It is still difficult to figure out the simple faults,crack,landslide surface,broken zone,soft layer and other geological interfaces.Based on above,this research is to do experiments of digital geophone,new generation high-precision surface wave instrument and imaging software based on the requirement of highway structure foundation disaster detection and the present situation and trend of nondestructive testing equipment.The transient Rayleigh wave method is used in this paper based on the theoretical basis of it,the method of the establishment of the observation system,the preprocessing of the signal and the analysis method and basis of the data.Taking the typical stratified geological demonstration point as an example,the relationship between dispersion curves of Rui Leibo is studied by means of forward and inversion methods.Taking the Yu Sui high speed geological exploration project as the survey area,the field observation method should be perfected.The transient Rayleigh wave method constructed by FLAC 3D provides evidence for equipment parameter modulation.From the experimental data and the results of simulation analysis,it is concluded that the transient Rayleigh wave method has been used to detect the soft layer of the self-developed equipment,which is of great engineering value and broad market prospect.The main contents of this paper are as follows:First,the seismic wave exploration methods and Rayleigh wave propagation characteristics are discussed in details,and the dispersion characteristics of the waves are deeply studied.According to the layout of common wild observation systems,making a set of proper detection methods for the demonstration site.The effects of source excitation conditions,channel spacing,offset and length of observation on signal collection and results are mainly discussed in detail.Secondly,in order to extract the dispersion curve,several common numerical analysis methods-the cross-spectrum analysis method,f-k method,the phase shift method and t-p method are applied,and the combined comparison method of the phase displacement method and the wave field analysis are proposed,which provides reference for drafting wild testing plans and FLAC 3D numerical simulation.Then,the finite difference software FLAC 3D is used to construct a three-dimensional model of the transient Rayleigh in the test field.Suggestions are made on model meshing,boundary condition processing,etc..The dispersion curve is used to guide the adjustment of equipment parameter integrity and consistency.The influence of trace spacing and offset on exploration accuracy and depth is studied,and a contrast model is established.The observation parameters of 1.0 m interval and 6.0m offset distance are established,which provides a certain reference for the formulation of field work test scheme.Finally,the detection and debugging of the surface wave meter are completed at the demonstration site.Combined with geological section and borehole information,get Rui Leibo signal.By inversion of dispersion curve by Geogiga Surface software,it is found that the distribution position of weak layer is 6.0 ~ 9.0 m,which is consistent with actual survey results.Then the instrument is applied to the design and exploration project,and the result error of stratification of geological prospecting is less than 5%.The consistency and accuracy of the exploration equipment are verified.