| With the vertical advancing of coal mining,the unloading of excavation in deep rock mass presents new mechanical characteristics.How to master the law of unloading effect of excavation in high stress roadway is of important significance to assure stability of surrounding rocks of roadway and high stress mining engineering.However,further studies on the mechanism of unloading effect of excavation in high stress roadway and the corresponding influencing factors are needed.Similar experimental studies on unloading effect of excavation have to be carried out and strengthened.Moreover,the internal correlation between the energy field in the excavated surrounding rocks and stability of the roadway also has to be solved urgently.In this study,a dynamic damage constitutive model of high stress rock mass in the high suction roadway Ⅲ13 in the Luling Mine in the Northern Huaihe Area was constructed by combining dynamic impact and static loading test of rock mass,multidisciplinary theory,indoor simlarity test,computer language and numerical simulation technology,as well as field industrial test.The rationality of this constitutive model was verified by the impact test and numerical impact test.The formula of unloading stress was deduced.Meanwhile,the mechanism of unloading effect of high stress rock excavation as well as the corresponding influencing factors was explored.An unloading system of excavation in high stress roadway was designed and developed independently,which was used to analyze changes of the stress field and distribution laws of damages in surrounding rocks under cyclic excavation.Besides,a three-dimensional numerical model of blasting excavation was established to explore the failure law and energy distribution of surrounding rocks in roadway under the action of blasting excavation.It was suggested to using elastic strain energy left in surrounding rocks as the criterion to determine stability of high stress roadway after excavation.Finally,a field industrial test was earried out to verify reliability of numerical analysis results.The major research contents are introduced in the following text.1)A dynamic damage constitutive model of high stress rock mass was constructed.Rock cores were drilled from the high suction roadway Ⅲ13 in the Luling Mine and prepared into rock specimens.Dynamic impact test and static test of rocks were carried out using the split Hopkinson pressure bar(SHPB)impact system and the RMT150C tester,through which the dynamic mechanical properties of rocks and relevant mechanical parameters were gained.The one-dimensional dynamic damage constitutive model of rocks was constructed by introducing in the ZWT viscoelastic model and statistical damage model.Subsequently,the one-dimensional dynamic damage constitutive model of rocks was fitted with the stress-strain curve gained from the dynamic impact test by using the Matlab to determine the material parameters of the constitutive model preliminarily.The subprogram of three-dimensional dynamic damage constitutive model was compiled by the Ls-dyna secondary development platform and Fotran language.This subprogram was input into dyna for the purpose of SHPB numerical impact test.Compared with the SHPB impact test,this SHPB numerical impact test based on this subprogram further perfected and modified the dynamic mechanical parameters.Finally,the three-dimensional dynamic damage constitutive model of high stress rocks was determined.2)The mechanism of unloading effect of excavation in high stress roadway was studied.Based on the unloading theory of elastokinetics,the mechanism of unloading effect of round roadway excavation in a uniform stress field was discussed through the residue theorem and inverse Laplace transformation.Stability of surrounding rocks in roadway and relevant influencing factors were investigated by using the tensile strength criterion.A finite element model of high stress roadway was established.In addition,the dynamic unloading effect of roadway excavation below different excavated sections in the non-uniform stress field was studied based on the secondly developed dynamic damage constitutive model.In the same time,the distribution laws of damages in surrounding rocks and internal correlation of initial geostress as well as influences of the excavated sections on damages in surrounding rocks were mastered.3)The unloading system of high stress excavation was constructed and a similarity test on the unloading effect was carried out.The unloading system of excavation in high stress roadway was designed and developed using the three-linkage amplification system and dynamic loads.A similarity simulation test of dynamic cyclic excavation in high stress round roadway was carried out based on the similarity theory by using the independently developed unloading system.In this test,variation laws of surrounding rock stress field with advancing of excavation surface during dynamic cyclic excavation in the non-uniform stress field as well as failure of surrounding rocks were analyzed.4)Damage laws and stability of surrounding rocks in blasting excavation of high stress roadway were investigated.A three-dimensional finite element model of blasting excavation was constructed.Key attentions were paid to study damage behaviors and elastic strain energy distribution of surrounding rocks in non-uniform stress field under the action of blasting excavation.The dominant factors that influence damage distribution were comprehended.It was proposed that reserving elastic strain energy in surrounding rocks is one of possible causes for instability of the high stress roadway.5)A field industrial test on surrounding rock damages under cyclic excavation of high stress roadway was implemented.Sxirrounding rocks in the high suction roadway in Luling Mine under cyclic blasting excavation were probed by geological radar and ultrasonic wave.Distribution characteristics of surrounding rock damages under cyclic excavation in high stress roadway were gained from radar profile and changes of sound velocity.Unckr the same stress conditions,the numerical simulation results vary from field measurement,which verifies reliability of the numerical simulation results.Fig[88]table[9]reference[190]... |
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