Discrete Element Analysis Of Strata Movement In Shallow Seam Repeat Mining

Based on the geological condition of 1203 working face in Daliuta coal mine of Shenfu Coalfield,the feasibility of UDEC-Voronoi modeling method is firstly discussed.Then,by means of theoretical analysis and UDEC-Voronoi numerical simulation,The law of the overburden movement of the high working face and the overburden hole in the high working face,the prediction index of the initial roof fault under the two conditions is put forward,and the theoretical formula of the basic ultimate limit span under the normal mining condition is selected.The main work of this paper and the beneficial understanding of the following:1.The rock uniaxial compression,uniaxial tension and straight shear numerical test based on the Voronoi-BPM model can simulate the experimental rock mechanics experiment and can be used for the calibration of macro-scale parameters.2.For the model size of 100 mm × 50 mm or 100 mm × 100 mm the best block length of 4mm,for other size models,the best block length only by the same scale can be scaled.3.The macroscopic parameters of the model are clearly related.When the parameters are calibrated,the normal stiffness kn and the stiffness ratio ks / kn should be calibrated according to the macro Poisson's ratio v and the macroscopic elastic modulus E.According to the macroscopic cohesion C and macroscopic The internal friction angle ? is calibrated for the mesoscopic cohesive force Ccon and the mesoscopic internal friction angle ?con,and the microscopic tensile strength Tcon is calibrated according to the macroscopic tensile strength T.4.The shape of the block mainly affects the shear behavior of the model.Due to the meshing effect of the random polygon block,the model failure surface is more rough,which greatly enhances the shear capacity of the model.The shape of the block has little effect on the tensile and compressive mechanical properties of the model,and the compressive,tensile and destructive forms of the two models are similar.5.The Voronoi-BPM and Trigon-BPM models can simulate the fissure initiation and development of rock mass.However,the Trigon-BPM model can not further simulate the collapse and compaction of rock mass due to the excessive concentration of tip stress.Therefore,the Voronoi-BPM model is more suitable for the simulation of the surrounding rock in the residual mining area of residual mining area and the breaking law of the old roof in the residual mining face.6.The Hoek-Brown strength criterion and empirical relation can be used to convert the rock-rock mechanics parameters of the coal seam mechanics parameters of the 1203 working face in Daliuta Mine.7.The structure of the arching structure shows the arch-arch-girder-beam evolution law.The overburden structure shows the rock pressure arch-the double rock Pressure arch-cantilever beam evolution rule,bearing structure showing pressure arch-double pressure arch-arch beam-beam evolution rule.8.Aiming at the prediction of the initial rupture of the old roof in the normal mining condition,the authors put forward the four characteristics of the pressure collapse height of the rock pressure arch,the vertical fissure length of the symmetrical position at both ends of the old roof,the thickness of the central part of the pressure arch dome and the surface subsidence curve index.9.For the calculation of the ultimate span of the old roof under the normal mining conditions,it is found that the arch calculation method is more suitable for the calculation of the ultimate span of the old roof by the beam and arch theory and the simulation results.10.According to the prediction of the initial rupture of the old roof in the condition of the overhill,the height of the stress zone of the coal pillar,the height of the rock pressure arch,the vertical fissure length at the symmetrical position of the old roof and the stress concentration Thickness and surface subsidence curve of five characteristics.