Application Research On Inverse Methods Computing Of Shear Wave Velocity Testing Data

In the seismic research field, shear wave velocity can not only reflect the propagation ability of seismic wave,it is also an important parameter to describe the dynamic characteristics of soil. In the project, we usually use shear wave velocity to determine the thickness of soi, identify the seismic liquefaction of sand or silt foundation or site classification of building, calculate the dynamic shear modulus of soil and so on.so it has actual engineering significance and theoretical value to research the shear wave velocity. For this complex geological body of soil, due to the difference of structure, origin, formation history and components, the shear wave velocity all showed significant differences in different soil layers and different conditions. For the shear wave measurement at home and abroad, on the one hand because of the limit of test means and condition, it increases the difficulty of obtaining the data of shear wave velocity or makes the test not ideal; On the other hand, after obtaining the testing data of shear wave velocity,in order to calculate simply, the shear wave velocity data are used to approximate treatment, it all bring a certain degree of error to the shear wave velocity test. Therefore, after getting the shear wave velocity data, how to not only simplely but also can calculate shear wave velocity of soil layer on the premise of ensuring its accuracy. This paper focusing on the data of shear wave velocity carry out the following work.1. The shear wave velocity testing are discussed in detail, analysed the application of CT(Computerized Tomography)technology in the treatment of shear wave velocity data, and introduced its content,development and application in the field of Geophysics briefly.2.Introduced the principle and method of various shear wave velocity testing instrument used in our country’s engineering widely.The scope of application of various instruments, various test methods and methods of data analysis are compared, their advantages and disadvantages are pointed out. And choice CT technology to single hole method which is widely used now.3.Introducted the theory knowledge of CT technology in detail,it is the geophysical inversion theory. It mainly introduces the concept of inversion theory, the mathematical and physical model, the characteristics of its solution. And emphatically introduces the research progress of seismic velocity inversion(CT) and solving method.4. Analysis using the travel time inversion imaging theory, simulate the method of single hole test, assuming inspired from the excitation to received from the receiving point travels in straight lines, describes the basic principles of single hole of CT Technology, at the same time, descripted how to achieve such a communication model in MATLAB.5. Introduced the basic principle of inversion algorithm, and introducted its specific process of using combined iterative method(SIRT) to solve the problems of traveltime inversion, and the concrete steps to achieve this process in MATLAB environment.6. Taking a project in Wuhu city as an example, choise two single hole test data for inversion calculation, comparative analysed the traditional calculation method and the inversion results, proved the correctness and feasibility of the straight path inversion algorithm, at the same time for its inadequacy and improvement are also presented.