Application And Research Of Well-Ground Seismic CT Technology To Karst Caves Survey

Well-Ground seismic CT method is a borehole seismic survey observation techniques. Than the traditional method of surface seismic survey seismic, data obtained by this method has a higher signal to noise ratio and resolution, more intuitive interpretation of results. This paper adopts Well-Ground seismic CT technology, exploration and interpretation the karst development scale and position of the nanjing metro line 3 form binjiang road to wutangcun sections. Focusing on the data acquisition and interpretation methods, proposing a new interpretation method based on "unit speed". First geological properties are classified as generalized as the formation of soil and rock layers, then the entire survey area is discretized into finite element grid. According to the ray tracing theory and the practical survey data calculates the unit speed, then draws the speed contour maps and determines the outliers by the different speed, in order to judge the size and location of the karst cave. The main results and conclusions of this study are as follows:(1) It has higher reliability by using Well-Ground seismic CT technology to determine the size and location of the karst caves. When the quality of a signal data is better, after filtering processing the karst waves can be directly judged through the waveform features, but there will exist certain error.(2) For not directly judging caves through the waveform features and the errors caused by wave judgment, can use "unit speed" method to process data. This method is simple and easy to operate, and the interpretation of the results accuracy can satisfy requirement.(3) The outliers of the rock mass conditions can also be found in the first-arrival time, just can not judge the specific exception type, but can be as a result of the verification.(4) Well-Ground seismic CT technology has wide range of application, low cost, high efficiency, easy operation etc, can be combined in different ways to meet the requirements of different engineering survey. According to the site conditions, using the heavy hammer to stimulate and 60Hz three-component geophone can meet the engineering survey requirements.