| Stepped slope will be formed in the surrounding area of open pit mining.Slope stability is the key to ensure safe and efficient production of open pit.Under the combined action of external factors such as atmospheric precipitation,groundwater,swelling deformation of expansive soil and creep deformation characteristics of rock and soil itself,the deformation and destruction of slope in stope and dump will become more and more serious.Once landslide occurs,it will cause loss of human life and equipment.It also crises the surrounding villages and the environment.In this paper,based on the engineering background of the Dailibaoqing slope,on the basis of field investigation and collection and analysis of previous geological data and rock and soil mechanics test data,the deformation and failure modes of the slope are numerically simulated and analyzed by FLAC3d software,and the stability of the slope of the dump is calculated and evaluated comprehensively and systematically in combination with the limit equilibrium theory.The specific conclusions are as follows:(1)Through on-site investigation,the hydrogeological conditions,stratigraphic characteristics and geological structure characteristics of Xianfeng Open-pit Coal Mine are summarized and analyzed,which provides basic information for the stability analysis of the slope of the Dailibaoqing dump.(2)The physical and mechanical parameters of rock and soil are tested,and the basic physical and mechanical parameters of soil are obtained:the average density of soil is 1.37 kg/m3,the average moisture content is 62.70%,which belongs to coarse-grained soil.The average cohesive force of soil is 24.4 kPa,the average internal friction angle is 19.3 degrees,the average compression coefficient is 0.85,and the average compression modulus is 5.66 MPa.The difference of principal stress and pore water pressure gradually increase with the increase of confining pressure.The axial stress of undisturbed soils and remolded soils increases first and then remains approximately unchanged with the increase of axial strain.Under the same axial strain condition,the axial stress of undisturbed soils is much larger than that of remolded soils.The basic physical and mechanical parameters of sandstone,weathered sandstone and weathered slate are obtained.(3)The factors of slope instability mainly include soil shear strength,water pressure,change of slope force,influence of well mining,nature and geological structure of slope rock and soil,slope shape and slope gradient,seepage force caused by groundwater seepage in slope,etc.There are five main micro-geomechanical models of slope deformation and failure:sliding(creep)-tension type,sliding type and so on.The results of numerical simulation show that the failure modes of dump are greatly affected by the original topography,and that the P1 and P2 profiles show a shear failure mode along the basement alluvium,while the P3 profiles show an arc sliding failure mode.(4)Based on the limit equilibrium theory,the slope stability is analyzed by theoretical analysis method.The results show that in natural state,the slope of the Dailibaoqing dump fully meets the requirements of the slope stability coefficient;under the influence of heavy rainfall,the overall anti-sliding ability of the dump slope is reduced;under saturated state,some slopes do not meet the requirements of the slope stability coefficient.(5)Under saturated condition,the local 2 position of P1 section.the local 4 position of P2 section and the oveall slope stability coefficient are all less than 1.2,which do not mect the requiremenlt of slope stability coefficient.The main reason is that the anti-sliding stability of local slope is reduced under saturated condition and the slope angle of single step is too large.(6)Aiming at the problem that local and short-term strong rainfall occurs in open pit coal mine during rainy season,and the gully formed by discarded materials and original stratum under the action of rainwater scouring,which leads to the decrease of slope stability coefficient,this paper gives reasonable and effective control measures and disaster warning equipment,and puts forward scientific and reasonable basis for similar slope disaster prevention and control. |
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