A Rock Mass Quality Evaluation Method Research In Karst Areas Based On The Technique Of Cross-hole Seismic CT

Rock mass classification is key research and concern problem in the survey, design and construction phase of underground projects. Based on plenty of engineering practices and researches, the scholars in domestic and foreign have got plentiful and substantial results on surrounding rock classification methods. But the level of surrounding rock is difficult to evaluate and the classification method is lack in the tunnels of karst region. This paper takes the karst areas of Nanjing Subway Line4as an example. Based on the previous research results, by using cross-hole seismic CT data of each section, selecting the elastic wave velocity as the evaluation index, I set up a special method for the rock mass quality classification of karst development area. The main content of the study are as follows:(1) By the investigation and study of the workspace engineering geological conditions, analyzing the main factors which control the karst development scale and form, the general karst development law in the workspace.(2) Analyzing all kinds of traditional rock mass quality classification methods, especially comparing each method in the selection of different evaluation index and its significance, theory basis for the proposed new indicators.(3) Research on cross-hole seismic CT technology, giving out a set of data processing method of getting the wave velocity contour map of each survey section according ro the technical principle.(4) Based on the wave velocity contour map of each survey section, defining a new evaluation index values of "V", seting up a special method for the rock mass quality classification of karst development area.(5) Practical application of the the rock mass quality classification of karst development area in Nanjing Subway Line4, give out the rock mass quality classification results of some survey sections and one hole survey line.