Study About Instability Criterion And Deformation Prediction Of Rock Slope Based On Fractal Theory

The deformation and evolution behavior of rock slopes are closely related to the environmental conditions and the geological structure of the slopes.It is always sudden,devastating and hard to control.If the deformation and evolution of rock slopes can not be accurately predicted and corresponding countermeasures can't be taken,it may cause immeasurable loss of life and property and cause huge social impact.In this paper,we use the fractal processing of three typical rock slope cumulative displacement monitoring data and compare the sensitivity of the HURST index to the rock slope surface deformation,which was obtained by two kinds of Rescaled Range Analysis methods.Then predicted the displacement of rock slope in Malanzhuang Iron Mine using Rescaled Range Analysis method based on the critical HURST index instability criterion.Based on the existing geological data,the numerical simulation is carried out using 3D laser scanning point cloud data,and the following conclusions were obtained:(1)The results of Rescaled Range analyzing based on the monitoring data of three typical rock slopes(Outang landslide,Daping landslide,and a rock slope in red zone)all show that the HURST curve obtained by using the time repeated-Rescaled Range method is more sensitive to the change in the surface deformation of rock slopes.It is more advantageous to use the critical HURST index instability criterion for early warning and prediction of rock slope.(2)By processing the GB-SAR monitoring data of the pit slope of the Malanzhuang Iron Mine,it can be seen that the broken rock mass in the middle parts of the eastern side of the pit has a relatively obvious displacement due to excavation disturbances,maximum displacement is about 50 cm.The results using Rescaled Range method analyzing of cumulative displacement curve of the monitoring points shows that during the excavation of the slope,the HURST curve of each monitoring point is greater than the critical HURST index during the entire stage,indicating that the slope is generally stable.(3)FLAC 3D software was used to simulate the excavation process of the pit.The results show that the stability coefficient of the pit decreases after excavation.The factor of stability after the excavation is 1.4,which means whole pit is still in a stable phase.This result is consistent with the Rescaled Range analysis result.The displacement calculated by numerical simulation is concentrated around the broken rock mass with poor integrity,which is in the middle part of the eastern side of the pit.This is highly consistent with the radar monitoring data,which further verifies the accuracy of the numerical simulation results.The failure mode of mine pit is that under the action of excavation disturbance,fractured rock and soil mass produces a large displacement and affects the overall stability of the slope.