Research And Application Of Precision Inversion Of Shear Wave Speed Test For Single-hole Soil

In the field of geological survey,the wave velocity test of the shear wave velocity of geological soil and rock strata has a great effect.It has the advantages of simple operation,high economic effect,high resolution and high accuracy.Extremely broad.Through the seismic wave velocity test,the elastic wave velocity of the soil can be obtained,which is the division of the site type,the calculation of the basic period of the site,the judgment of the liquefaction of the site sand and the silt foundation,the determination of the soil dynamic parameters,and the seismic plot The division provides a reference and basis.However,the main method of solving the shear wave velocity is to obtain the shear wave velocity of the rock and soil layer by picking up the seismic travel time information by surface wave method,single hole method and cross hole method.The premise of this in situ test technique is that the seismic waves are propagated along a straight line and that the underlying media are evenly distributed,but the actual soil distribution is nonuniform and therefore a hypothetical error is generated.In this hypothetical case,On the one hand will lead to lower accuracy of the test wave speed,on the other hand can only find the average velocity of the plane where the survey point can not reflect the actual wave velocity distribution of this plane.Therefore,this paper attempts to study and find a convenient,fast and accurate method for calculating the shear wave velocity by simulating ray tracing.Ray tracing simulation has a great advantage in the calculation of seismic waves.It has the advantages of high computational efficiency and fast calculation,and it can clearly see the advantages of the ray path.It is a kind of earthquake,such as forward modeling,seismic imaging Signal processing and computing applications is very common.The research ideas and methods of this paper are based on the predecessors ray tracing theory,and the theory and method are applied to the near-field wave velocity test.The focus of this paper is to start from the two aspects of forward modeling and inversion to study the contents of the positive and negative argument.Positive ray tracing is based on travel linear interpolation(lti ray tracing),which has a greater advantage in simulating seismic wave propagation paths.Inverse calculation of shear wave velocity using the joint iterative reconstruction method(SIRT),which has the advantage of the algorithm is stable,high convergence,and can quickly calculate the large linear equations.In this paper,the two superiority of forward and inversion methods are combined to compile the algorithm into MATLAB programming language,and the algorithm can beused to simulate and calculate the seismic wave propagation path and soil shear wave velocity.Specifically carried out the following work.1.Two algorithms for calculating the shear wave velocity of soil layers are presented,and the superiority of the two algorithms and the basis of theoretical basis and programming algorithm are introduced in detail.2.This paper introduces the application value and significance of the shear wave velocity test in soil and the three kinds of in situ testing techniques.Through comparative analysis,the advantages and disadvantages of each method are pointed out.3.The principle and law of seismic wave propagation are introduced in detail.This paper introduces the development of ray tracing theory and the linear interpolation(LTI)ray tracing method used in this paper,and introduces its theoretical basis,modeling method and algorithm realization process.And apply it to three different models,and compare with the traditional shortest path ray tracing results to verify the superiority of the algorithm.4.This paper introduces the principle of geophysical inversion and the reason of the joint iterative reconstruction inversion,and introduces the principle and implementation steps of SIRT inversion algorithm in detail.5.The feasibility and validity of the ray tracing algorithm are validated by comparing the computational value of the program with the measured data of the original engineering,which is applied to the actual engineering project.Summarizes the advantages and disadvantages of this method.