Abstract:

Longyou grottos, the ancient underground grottos with the characteristics of shallow embedding, large span and some others, have been attracting many experts of rock mechanics and engineering geology coming to research. Recently, many positions of the roof of grotto No.3 have the phenomenon of cracking and exfoliating. The data of strain meters installed on the steel pillars which have the function of supporting the grotto are also changed. What the strength of rock pillar No.3-2 decreasing leads to the adjusting of strength condition of rock around is thought to be one of the main reasons causing the changes mentioned above. With the aid of FLAC3D, the paper simulates the changes above caused by the strength decreasing of rock pillar No.3-2, using the main fundamentals of strength reduction technique for reference. The results of the numerical simulation explain the changes get by monitoring. Based on which, the paper analyzes the change of stress of the roof and other rock pillars of grottos No.3 in the process of deformation and failure of rock pillar No.3-2. By the research, the authors get the points: ① The strength of rock pillar No.3-2 has been decreased a little; and still it is in the process of continuous decreasing. ② The cracks on the roof will be longer and more in the process. The conclusions provide a basis for analyzing reasonably, forecasting the strength state of grottos and protecting the grottos in the process of deformation and failure of rock pillar No.3-2.

Key words: Longyou grottos, strength decreasing, stress change, FLAC3D, monitoring