Study On The Stability Dynamics Evaluation Model Of Falling Dangerous Rock Masses On Slope

Most of the analysis parameters in the stability evaluation model of dangerous rock masses cannot be measured dynamically in the field,and the commonly used slope monitoring indicators cannot quantitatively evaluate the stability of dangerous rock masses.In order to solve the above problems,this thesis investigates the dynamic evaluation model for the stability of falling dangerous rock masses,with a view to realising the quantitative evaluation of the stability of dangerous rock masses based on monitorable data and the calculation of monitoring index thresholds during the failure and destabilisation of dangerous rock masses,the main works carried out in the paper are as follows.(1)The force-deformation characteristics and damage mechanism of falling dangerous rock masses were analyzed,and it had found that the crack depth at the rear edge plays a controlling role in the stability of dangerous rock masses.It also found that the natural frequency index is sensitive to the change of the crack depth at the rear edge of falling dangerous rock masses and has good measurability through model experiments.(2)Based on the relationship between the natural frequency index and the slope constraint of falling dangerous rock masses,a formula for calculating the constraint stability coefficient of falling dangerous rock masses based on the natural frequency was proposed,and a model for evaluating the the stability of falling dangerous rock masses was established.(3)An elastic half-space volume-foundation vibration model for falling dangerous rock masses was proposed,based on which the expressions for the boundary conditions and vibration functions of dangerous rock masses were derived,and the formulae for calculating the natural frequencies of dangerous rock masses were determined;the formulae for calculating the relative depths of critical cracks when dangerous rock masses break were derived,and the calculation methods for the parameters in the model for evaluating the natural frequencies of the stability of dangerous rock masses were determined.(4)Damage experiments were carried out based on similar models of different sizes of critical rock masses.The validity of the model for evaluating the critical rock mass stability based on natural frequency was analyzed.The experimental results show that the average error between the calculated and measured values of the natural frequency of the dangerous rock mass was 3.85%,and the average error between the calculated and actual values of the constrained stability coefficient of the dangerous rock mass was 2.97%when the natural frequency of the bending vibration in the vertical plane of the dangerous rock mass was used as its stability evaluation index.(5)The calculation method of the threshold value of the natural frequency index for the failure of dangerous rock masses under different working conditions was determined by taking the failure probability of dangerous rock masses in different cycles as the analysis working condition,and the application of this method and the evaluation model of the natural frequency of the stability of dangerous rock masses was carried out with an engineering case.(6)Proposed a remote measurement method of dangerous rock mass vibration and the evaluation method of dangerous rock mass stability combined with numerical simulation,solving the key problem of the application of the evaluation model of the natural frequency of dangerous rock mass stability in difficult-to-reach and structurally complex dangerous rock masses.