Study On Failure Mechanism And Forecasting Models Of Instability Of High Rock Slope

Stability of high rock slope is the most characteristic problem among engineering geology region, which is not only concerned in engineering safety itself, but also is concerned in safety of integrated environment. Studies on failure mechanism and deformation forecasting models of high rock slope were the focus and difficulty problem of engineering geology since 1960s.Slope angle of Daye open iron mine was 43～60°, part locality reached 70°, height of which was 230～430m. Up to now, the slope of Daye open iron mine has been existed over 10 years, effected by rain and blasting, the slope existed as a state of limiting state of equilibrium, and the stability coefficient was 1.0～1.1. Collapses and slopes in large scale would occurred in part locality effected by open mining in high slope foot and non-pillar sublevel caving beneath high slope, which would incurred impact pressure to underground stope and disturbed the normal operation of Huang-Shi State Mine Park. There would be significance both in theory and practical production, if studiers could master the deformation process of instability accurately, could estimate the stability state and judge the failure model and failure time scientifically at different slope deformation evolvement period.Aim at methods in studying landslide forecasting were simplex and impractical studied achievements, incorporated innovation and new method in deformation mechanism of high slope, based on consulting abundant references on landslide forecasting home and abroad, methods of stereographical projection, FLAC numerical simulation, grey theory, time series, BP artificial neural net and maximum likelihood estimate were synthesized to study failure mechanism and deformation forecasting model of high rock slope "Area A" of Daye open iron mine from three aspects: geological structural, mechanics mechanism and deformation forecasting.Followings were dissertation's main research work and conclusion:1) Engineering geology characteristic of high slope Area A were studied and results show: slope lithology of Area A can sum up to Diorite Petrofabric, Alteration Diorite Petrofabric, Faultage crush zone Petrofabric and Magnetite Petrofabric; the earth stress of open mining stope consisted in gravity mainly, and the relic structure stress was neglectable; the rock structure of high slope Area A were complicated, dominant structures can reduce to three groups:①Bedding structures that strike NE dip SE;②Bedding structures that strike NW dip SW;③Anti-dip structures that strike NE dip NW.2) Rock mass structures of high slope Area A were analyzed by stereographical projection method, and results show: Collapse modes of slope were toppling and wedge-shaped destruction in small scale, the direction of wedge-shaped destruction is SE30°; Bedding landslide and wedge-shaped landslide occurred possible in lower part of slop, and the direction of bedding landslide was SW10°～20°, direction of wedge-shaped landslide was SE20°～30°.3) Deformation & failure mechanism of high slope Area A were simulated by FLAC-3D numerical simulation software. Geology-mechanics model were recapitulated firstly based on engineering geology datum and rock mass structure analysis of slope Area A, then numerical analysis model were established through AutoCAD and ANSYS. Numerical simulated results show:①The maximum and minimum principle stress changed few basically in course of excavation, which distributed bedded along slope. And the maximum compressed stress distributed in model's right bottom, the maximum tensile stress distributed in each steps' head in small scale;②The shear stress of slope increased with excavation depth increases, also increased with slope angle increases, the shear stress distributed in slope foot of north side larger 1.0 MPa than distributed in slope foot of south side. When excavated to ultimately level -156m, compressed shear stress distributed in superficial slope of north side was 0.50～0.75 MPa, tensile shear stress distributed in superficial slope of south side was 0～0.25 MPa;③In course of excavation formed the slope, horizontal displacement of slope rock mass was greater than vertical's. The maximum displacement of vertical direction was 0.21m, which presstered to -22m leveling bench of north side ( F9' faultage cursh zone emergence position ). The maximum displacement of horizontal direction was 0.34m, which presstered to -60m leveling bench of north side ( A10 broken belt emerengence position ).④Along with scope and depth increase, slope plastic zone increased gradually. When excavated to finally level -156m, there was a swath of plastic zone transfixed favorable in superficial slope of north side.4) Basic characteristics of landslide forecasting theory and concerned methods in being were summarized in the paper. Incorporated studied contents in the dissertation, elementary theory, modeling idea and step of GM(1,1) theory, curvilinear regression analyses, time series and BP theory were introduce detailed.5) Different time scale multi-forecasting models of instability deformation of high slop Area A were studied, and the results show: In aspect of short-term forecasting model, the forecast effect of Grey-ANN composite model ( average relative error was 1.52% ) is better than conventional GM (1,1) model ( average relative error was 9.33% ) and improved GM (1,1) model ( average relative error was 9.23%); In aspect of medium term forecasting model, the forecast effect of BP ANN model ( average relative error was 0.6% ) is better than polynomial regression model (average relative error was 8% )and ARIMA(p, d, q) model( average relative error was 7%); In aspect of long term forecasting model, the maximum likelihood theory considered global and randomness and BP-ANN method based on compound evaluating indicator of stability of rock mass analysis is better than conventional limiting equilibrium method, the stability coefficient of anterior were more approximate with practical situation.6) GMD forecasting model was discussed in the dissertation. Comparatively detailed modeling thought and technical method were put up referred a few concerned research datum. Incorporated practical engineering of high slop Area A, rationality and availability of failure mechanism and various forecasting models achieved by the dissertation based on GMD thought were testified in three aspects: slope stability validation, slope failure mechanism validation and slop key-point deformation dynamic tracking.Finally, based on research contents and conclusions in the dissertation, some suggestions in further studies were provided.