Research on Prediction of Wall-Rock Quality for Underground Caverns during Geotechnical Surveys
YUAN Guang-xiang;LI Jian-yong;DONG Jin-yu;HUANG Zhi-quan;WAN Jun-li;WANG An-ming;School of Resources and Environment,North China University of Water Resources and Electric Power;Xinjiang Institute of Engineering;China Academy of Railway Sciences;
Assessment of wall rock quality is important to the design and construction of underground caverns. All codes for geotechnical surveys have definite rules for the wall-rock quality assessment. The methods to evaluate wall mass quality have a large number, but their prediction results tend to be much different from real situations in a survey stage. The reason is that such assessment needs many accurate data, but the direct data of surrounding rock is usually limited in the survey stage. Most data are indirect data(from geophysical surveys) and inferred data( based on surface geotechnical mapping and drilling) data. Thus, it is impossible to well assess wall rock solely relying on a single data set. This paper presents an improvement to this aspect based on analysis of multiple data. Using data from surveys, the relationship between the drill core quality and the logging data is established. Then we examine how the quality of wall rock relates to each geophysical parameter. Finally, comparing geophysical profiles and drill data permits to help predict the features of wall rock. As an example, we compare curves of BQ, RQD, log and an electromagnetic profile of a drill hole in granite and known wall rock quality. We find that the geophysical anomalies correspond roughly to the quality of the wall rock quality. It means that comprehensive analysis of geologic, geophysical and drilling data can help improve the prediction of wall-rock quality during geotechnical survey.