| The selection of rock mechanics parameters is one of the most fundamental tasks to evaluate the stability of high rock slope.However,the rock mass which has the characteristics of non-uniformity and uncertainty has also caused the selection of rock mass mechanics parametersshowing the features of uniqueness and fuzziness.Therefore,how to select rock mass mechanics parameters in a scientific and reasonable wayto evaluatethe slope stability is extremely important. Given that we should ensure the good design and safe operation of slope engineering, it is of great significance to make a in-depth study of rock mechanics parameters.This paper, based on the project of "The comparison and optimization of slope stability research of Huangshan limestone mine in the Emei city ", aims to carry out research on rock mechanics parameters and slope stability. The mine strata is a consequent slope which tends to be consistent with the main slope,the main available mine strata arePermian MAOKOU group and QIXIA group. As severe potential problems exist as a result of layers of weak structural plane and poor mechanical properties,the weak intercalations of permian LIANGSHAN becomes the main factor of affecting the stability of slope. Along the history, a number of bedding landslideshad occured in the mine, which caused significant personnel and property losses.In the paper,three steps are taken.First, on the basis of the engineering geological informationcollected, the author analyzes through detailed field geological investigation,by combining the formation process of weak intercalations from the weak interlayer material, the tectonic movement and the groundwaterwith weak interlayer mineral composition and particle composition to analyze the strength characteristics of influence factors. Second,the mechanical parameters of weak interlayer is determined by means of the in-situ shear test, indoor shear test and sliding back calculation results with parameters. According to the engineering geological zoning, RQD classification, CSMR classification method and correction of BQ-RSlope methods are applied for rock mass quality evaluation, combining with RocLab program, with the application of Hoek Brown strength criterion, the strength parameters of the rock mass is estimated. Third,for the purpose of providing the basis for the design of mine and production safety,the author attempts to establish the slope engineering geology numerical simulation model and then carry out the slope stability of numerical calculation applying FLAC3D, to make analysis and evaluate of theslope stability of open-pit mine.This article mainly includes the following results:(1)Through the investigation and research of the weak intercalation in the Huangshan mountain limestone open-pit mine slope, we begin to realize that the formation of the soft interlayer is a complex and long geological history process. The formation of weak intercalations has the necessary material base, tectonic movement and the effect of groundwater in the region. The cause of rock with multi-layer soft interlayer and the weak interlayer are mainly argillaceous limestone and mud sandy limestone.P11-3 is mainly argillaceous limestone containing carbon, which is the main group stratum throughout the area.Influence factors of soft interlayer mechanical parameters is discussedin the aspect ofnature and environmentweak interlayer which determine the weak intercalations mechanical parameters of fuzziness and complexity according to the weak intercalations of mineral composition and particle composition of the test result as well as the development features of weak intercalations.Among natural attributes, it mainly includes the mineral composition, particle size composition and thickness of the soft interlayer,etc; environment mainly includes the influence of in-situ stress and groundwater.Adapting many different kinds of methods to value the shear strength parameter of weak intercalation and using the in-situ shear test and shear test, the preliminary shear strength parameter of weak intercalation is given.On the basis of engineering geological characteristics of the investigation at the scene, sliding mechanism of the landslide is analyzed. Mining landslide belongs to the traction type, slip-cracking as the main form of expression. The landslide is in the failure of the internal and external dynamic function, special geologic structure and stratum lithology are the main internal factors of landslide, unreasonable excavation way, blasting vibration and rainfall are the principal causes of Iandslide.In combination with the morphology and properties of landslides, restoring the previous landslide sliding state of geometry and stress state, the shear strength parameters of sliding belt is carried out according to the principle of the algorithm for inverse calculation. Finally, in the way of the comprehensive comparison the analysis shows that three methods for the strength of weak intercalated parameter value are closely. The strength of the parameter of in-situ tests is smaller than that of indoor shear test, much more closer to the actual situation,while the algorithm gets a whole section of the average shear strength. On this basis,a suggestion of weak intercalations parameter is given:C=0.04MPa, φ=29° (natural condition); C=0.01MPa,φ=24°(saturated condition).(2)The mining area can be divided into Ⅰ area, Ⅱ area and Ⅲ area according to the mining area of topography, rock mass structure and engineering geological zoning features of the engineering geological petrofabric.Then, with the application of RQD classification, CSMR classification and correction of BQ-RSlope are applied for rock mass quality evaluation, every way verify each other. The results show that the classification system of RQD characterization of slope rock mass quality classification in mining area is poor-general; CSMR classification system characterization of slope rock mass quality classification mining area between Ⅴ～Ⅱ; BQ-RSlope classification system characterization of slope rock mass quality classification mining area is between Ⅴ～Ⅱ. The whole slope rock mass quality is poor because of the regional structure and the influence of blasting vibration, I area of rock mass quality is better than that of Ⅱ zone of rock mass quality, Ⅲ area of rock mass quality is the worst, the evaluation results is consistent with actual situation in the mining area; the rock mass of Maokou group and Qixia group is broken, and their rock mass quality is poorer; the Liangshan group has a quality of V which formats throughout the area,though it has a big thickness, it will melt and crack if it reacts with water then its strength will be reduced sharply. Rock mass quality of Dachengsi group is classified for Ⅱ level, and the layer structure of rock mass is laminated as well as the layers with good combination and high strength-Therefore, it is suggested that the ordovician sandstone should be the the bottom layer.Finally, with application of the RocLab, the rock mass mechanics parameter is given by using Hoek-Brown criterionaccording to the results of rock mass quality evaluation.(3)Through stimulating numerical calculationin terms of the huangshan mountain limestone open-pit mine slope, the resultswith the slope of displacement field, stress field and plastic zone and the shear strain increment analyzedshows thatthe open-pit mining process is a complex dynamic process. In initial stage of excavation, the excavated rock mass volume is little, also its displacement is small, with the springback deformation, the plastic zone and shear strain increment are very smallpointing in the direction airport surface. As the progress of the deep excavation slope, its displacement and plastic zone increases, the shear strain increment also gradually throughout the area. Excavation of the rock mass are continually in the process of excavation unloading and blasting vibration, the influence of such factors lead to rock mass produce new cracks, and the rock interlayer adhesion strength is reduced, then generate cumulative damage of rock mass. With the deepening progress of the excavation, there will be more engineering geological problems which has a feature of slope stability than ever, therefore, the slope stability evaluation should be combined with feedback after slope excavation. |
PDF Full Text Request