Vibration Characteristics Of Falling Unstable Rock Under Different Stability States

Unstable rock mass is a serious global mountain hazards problem. With the extreme climate happens frequently in recent years, the influence of unstable rock mass has increased gradually. So some important industries that matter vital to the national economy and the people's livelihood put forward new requirements to the detection, evaluation and early-warning of unstable rock mass, such as railway, highway and water conservancy project, etc. However, the various ways to detect and evaluate the stable state of unstable rock mass have their own shortcomings, leading to the difficulties to evaluate unstable rock mass accurately and efficiently. Therefore, it has become a problem that should be solved urgently on how to form a new way to detect and evaluate the unstable rock mass quickly and efficiently. This paper does the research on the vibration characteristics of falling unstable rocks in different stable states, which based on the Research about the Detection Technologies and Devices Based on the States of Non-contact Railway Unstable Rocks(J2014G006), the project of Railway Science and Technology Research and Development Center of China Railway Co. and the Research about the Stable States of Unstable Rock Based on the Vibration Characteristics(DZ2014001), the project of the Innovation Base for the Geological Engineering Graduate Students of Guizhou Province, with the system of interdiscipline as theoretical basis and methods, such as rock mechanics, structural dynamics and modern testing technology, etc., taking falling unstable rocks as the object of the research and using the combination of theoretical analysis, numerical simulation and indoor and outdoor tests as researching methods. The main research contents and innovation points of this paper are as follows:(1)Making theoretical analysis about vibration characteristics of unstable rocks based on the studying of evaluation methods and detection and evaluation technologies of unstable rocks, knowing about research status of vibration characteristics of unstable rocks and analyzing its shortcomings, and establishing theoretical analysis model and related mathematical analytical formulas, which can make contrastive analysis with indoor simulation tests. The research shows that the overturning safety ratio of unstable rocks in the situation of harmonic excitation has a positive correlation with its predominant frequency. According to several available empirical values of structural plane of unstable rocks in the wild, give the relation curves about using predominant frequency of unstable rocks to estimate its risk degree.(2)Through the dangerous rock stability and vibration characteristics of the numerical simulation analysis, the finite element model of dangerous rock is established, and the mechanical model, the natural vibration analysis, vibration analysis, clear the vibration characteristic of the dangerous rock under different solid state;Then established by indoor experiment dangerous rock vibration feature detection method, has been clear about the dangerous rock stability evaluation index, and analyzed the dangerous rock solid degree rule: the influence of the evaluation indexes for contact with the bedrock of dangerous rock stability, the vibration of the dangerous rock and rock the greater the difference. The vibration response of dangerous rock is more obvious and the slower vibration attenuation, excellent frequency and damping ratio of dangerous rock is reduced, the dangerous rock and bedrock of RMS acceleration amplitude ratio increased.(3)Through statistical comparison of numerical analysis. Laboratory test and field test of the three methods for different solid state of dangerous rock is remarkable frequency, damping ratio, the RMS amplitude ratio. The vibration characteristics and its dangerous rock solid state. The corresponding relationship between established based on the vibration characteristics of solid state of dangerous rock is excellent frequency- the RMS amplitude than the combination evaluation method, the damping ratio- the RMS amplitude ratio combination evaluation method. This method is based on the RMS amplitude ratio of dangerous rock is abscissa, excellent frequency and damping ratio of ordinate respectively. In the heart of the established a two-dimensional plane coordinate system dangerous rock solid state is divided into safety zone, a safer area. The danger zone, a dangerous rock area, caving area.