Research On Crack Propagation Law And Roadway Stability Under Blasting Dynamic Loading

In recent years,with the continuous development of China’s economic construction,the scale of mining projects and other geotechnical engineering has been continuously expanding.Blasting technology has also been widely used in engineering fields such as mine exploitation and roadway excavation,but blasting technology is the project.While bringing convenience,it also brings hidden dangers to the stability and safety of the project.The problem of rock mass destruction and rock mass stability under blasting dynamic load is getting more and more attention.Therefore,it is of great practical significance and theoretical value to study the blast dynamic load on the rock crack propagation and roadway stability.First of all,the influence of various factors on rock crack propagation under dynamic loading during blasting is different.Based on the orthogonal test design method,the initial crack length,crack inclination angle,number of cracks,blasting dynamic load and elastic modulus,Poisson ratio,and density are selected.Influencing factors are main controlling factors,and 18 different numerical calculation schemes are designed.Through the analysis of the orthogonal analysis of rock crack extension length and acoustic emission number under different schemes,it is found that the blasting dynamic load has the greatest impact on the rock crack propagation,followed by the crack dip,crack length,and finally the number of cracks;at the same time,the rock mechanics parameters affect crack propagation.It also has a certain effect,in which the elastic modulus has the greatest impact on the rock crack propagation,while other factors have less effect.Then,based on the Griffith energy release theory,a calculation model of rock mass crack propagation under dynamic load is established.The effects of charge amount,blast center distance and elastic modulus on rock crack propagation are studied.The results show that when the charge volume and elastic modulus are constant,the crack propagation length decreases rapidly with the increase of the burst center distance within a range of 100 m from the blast center distance.When the blast center distance and the elastic modulus do not change,a single stroke occurs.The length of crack propagation under rock blasting increases linearly with the increase of charge.When the charge is greater than 150 KG,the crack growth speed at the same blast center distance increases rapidly with the charge amount;When the blast center distance is constant,when the elastic modulus is less than 60 GPa,the crack propagation length decreases rapidly with the increase of the elastic modulus under a single blasting.Next,the rock crack propagation under different blasting parameters was numerically analyzed using RFPA software.The results show that when the charge volume is 300 KG,the blast center distance is less than 125 m,and with the increase of blast center distance,a single blasting The crack propagation length decreases rapidly;at the same time,when the elastic modulus is greater than 50 GPa,the crack propagation length change produced by a single blast tends to be gentle as the elastic modulus increases.The numerical calculation results and the theoretical calculation results of the rock crack propagation length under blasting dynamic load are compared and analyzed.The relative error of the calculated results of the two methods is less than 10.6%.It shows that the rock crack propagation calculation model under the blasting dynamic load can reflect the formation and expansion of cracks.Finally,taking Jinshandian iron ore as an example,based on the above research results,improvement measures have been proposed for blasting and roadway support in Jinshandian iron ore mine.In the blasting aspect,the maximum single-stage initiation charge is controlled within 150 KG.The time interval for each blasting is set to 25-50 ms.At the same time,the top air interval is used for the uncoupled charge structure,and a small V-type initiation method is designed.Roadway support for roadway support,roadway within 100m~125m from the blasting site is supported by key support,and the elastic modulus of surrounding rock after the support is more than 60 GPa.The results of the dissertation provide a theoretical basis for the evaluation of blasting roadway stability under dynamic load,blasting control and roadway support.