工程场地条件的脉动研究

The key points of the scheme and the general situation of the project with title of Microtremors observation analysis on engineering site condition (59978048) are reported in this final report. The main progress and achievements obtained in this project are described in detail, the international cooperation and the training of post graduated students are presented, the outlay is reported briefly and some problems and suggestions are also mentioned in the report.Local site condition, especially soil condition, has a great effect on the earthquake damage and strong ground motion. In studies of site condition effect on ground motion, the shear-wave velocity structure of the site is the essential information. To develop a convenient, inexpensive and stable survey method, especially one can be widely used in urban area, is a significant task in study of earthquake engineering and geotechnical engineering. The evolution, state of the art and the trend in future are systematically reviewed, the significance of microtremors array observation and necessity of study on approach of inverting site shallow shear wave structure from the data of microtremors are emphasized in the project.The design principles and layout of the Sino-Japan joint observation arrays at four sites in Tangshan and Xiamen, and the instruments and equipment adopted are introduced. The 219 records from the observation are processed..In order to take apart definitely and distinctly the main difficult points in this complicated problem of inverting site shear wave velocity structure by means of microtremors observation, the authors of the report present an idea of virtual inversion. By this way, one could make sure if there is imperfectness in microtremors observation and analysis, or if the inversion procedure is effectiveness. The calculated transfer function, Rayleigh wave and Love wave dispersion curves of soil layers, from the known shear wave velocity structure of the selected or assumed site models, are taken as the inversion object curves respectively. Some matters in microtremors observation, instrument system and analysis are segregated from the whole inversion procedure. To study inversion technology in a relative closed area, it is easier to find problem, evaluate effectiveness and make improvement..The Genetic Algorithm (GA), as an artificial global optimization method, could search many modes simultaneously without any calculating partial derivativeness. While there is a difficult in problem that the result is often affected by the initial mode, and the calculation of partial derivatives is very hard, in the traditional inversion procedure. Therefore, the GA has been applied successfully in many fields. In this project, the genetic algorithm for inverting the soil shear wave velocity structure is designed. The shortcomings in traditional GA, the weak local search effectiveness and too early convergence, are improved by selecting better operators and adding additional genetic operation. Furthermore, a hybrid procedure of GA combined with simplicity form is also adopted, in the inversion of Love wave dispersion curve of the site soil layers..According to the wave type transmitted in horizontally layered media, the object of virtual inversion is chosen as: 1) the calculated shear wave transfer function; 2) the calculated dispersion curve of the first mode Rayleigh wave, 3) the calculated dispersion curve of the first mode Love wave, all from the dynamic parameters of the site soil model. In this project, the transfer function of shear wave propagating in linear elastic or visco-elastic soil layers is calculated by the multiple reflection theory. The dispersion curves of the first mode Rayleigh wave and Love wave respectively propagating in elastic soil layers are calculated by the improved Haskell transfer matrix method. A set of computation program is compiled. Furthermore, the sensitivity of the curve to the soil parameters is compared.According to the detail of the site information obtained before the inversion, three sets of genetic op

在调研总结国际上用地脉动观测探查场地土层结构技术方法的基础上，惧整理地脉动观测记录，分析长周期地脉动与场地构造的关系。研究用地表地脉动水平和竖向分量的谱比推算场地传递函数和利用地脉动中撮的相速度反演场地土层速度构造的方法。为我国制定场地地脉动观测技术要求奠定基础，为我国场地勘察技术的进一步简便、经济，做好知识准备。