Development Of Loading System Using Static Cracking Agent For Blasting Failure Law Of Brittle Material In High Stress

With the gradual consumption of mineral resources in the shallow,more and more mines get in the period of the deep mining.Roadway excavation and mining are all in high stress environment in deep mining of which environments with three high and one disturbance.At present,drilling and blasting method is the main method of roadway excavation and mining in deep metal mine.It is guidable for blasting parameters design and parameters optimization in deep to analyze the effect of high stress to blasting,based on the research on the size and shape of fracturing zone,fragmentation degree and the spread law of blasting crack in rock in high stress environment.Physical experiment is one traditional method to study the mechanism of rock fragmentation by blasting under high stress condition.In order to simulate the blasting in similarity material with physical and mechanical property approximate to that of rock,a new biaxial loading system with high blasting vibration resistance and steady load uses static cracking agent(SCA)to meet the requirement of loading device in the blasting experiment.Using the new loading system,the mechanism of brittle material fragmentation by blasting under high stress condition is analyzed through physical experiment and theoretical analysis.Firstly,swelling mechanical behaviors of SCA in cylinder with radial constraint are researched to analyze its output rules of axial swelling pressure through physical experiment,and evolution rules of its key parameters through numerical simulation.Secondly,an experimental system uses SCA as power source has been developed,which can be used in the field in situ experiment with high steady load,load controllable and blasting vibration impact resistance.The mechanism of brittle material fragmentation by blasting under different high stress condition are analyzed using the loading system.Finally,mechanism of brittle material fragmentation is revealed with coupling effect of different static stress and dynamic blasting stress.The specific studies are as follows:(1)The swelling pressure measurement system is designed based on the hydraulic characteristics of SCA swelling pressure.Rigid cylinder axial output method and its optimal measuring parameters,swelling pressure measuring calculation formula are proposed for swelling pressure of SCA.On the basic of axial-output principle,swelling mechanical properties of SCA,such as changing law of radial and axial swelling pressure with various diameters,the relationship between radial and axial swelling pressure,the reason of self-sealing effect under different height-diameter ratio and different reserved free space,are studied to offer design parameters for experimental system to output controllable load.(2)The numerical model of SCA hydration swelling is established by finite element program ABAQUS.To make the simulation results match the physical results through normalizing the curve of swelling pressure and adjusting calculating parameter,is meaningful for studying change law of Elastic Modulus,Poisson Ratio,and other parameters in SCA swelling process.Based on Elastic Modulus curve changed with principle stress,Elastic Modulus stress strengthening can be established to offer effective mechanics parameters for SCA application.(3)A new biaxial loading system,of which load-bearing capacity attains 800 kN,uses axial swelling output of SCA as power and equips with high blasting vibration impact resistance,can realize full range loading of static stress for similar model sample.A controlled method of axial force output is present through adjusting the swelling volume in hydration expansion process based on output curve and loading scheme of similar material.The results show that,the system with good adaptation to outdoor experimental environment and loading controlled method are easy to carry out.(4)The blasting experiment of brittle material with similar model sample is designed to study the coupling effect of using the new loading system.The blasting effect data,such as the distribution of blasting cracks,the shape,size and volume of blasting fracturing zone,are analyzed to discuss the influence of schemes with different stress combination on the condition of non-static stress,uniaxial static compressive stress,and biaxial static compressive stress with same values.(5)After theoretical analyzing distribution law of stress,strain in brittle sample under dynamitic stress,linear component strain expression and positive stress component expression at the radial crack surface and reflected radial crack surface are got.The influence of static stress to the above crack is discussed.The formation mechanism of blasting crater under coupling effect of dynamitic blasting stress and static stress,fragmentation mechanism of brittle material under high stress are revealed to provide reference for blasting design in deep metal mining.