Study On The Distribution Of Dynamic And Static Stress Strain In Rock Impacted By Abrasive Slurry Jet

Aiming at solving the problems of narrow work space,serious tool wear,and low mining efficiency existed in mining the thin seam with complex geological structure,the research group put forward a new method,abrasive slurry jet(ASJ)united with cutting tool,to cut rocks,which can make it realized that safe and efficient mining of complex geological thin seam.And the research on the mechanism of rock broken by ASJ is the basic and key part to develop the new method.In order to reveal the mechanism of rock broken by ASJ,the paper systematically carried out a study on the stress and strain distribution of the impacted rock.The main contents are as follows.Firstly,the flow field characteristics of ASJ were studied to analyze the velocity field and spatial distribution of slurry jet and abrasive particles.Then,on the basis of the above research,a mathematical model of static stress distribution in rock impacted by ASJ was established to explore the form of stress concentration in the rock,and to analyze the areas and styles of rock failure.And a corresponding numerical simulation was conducted,whose results verify the correctness and reliability of the mathematical model.Besides,three studies were carried out successively,numerical simulation,experiments with non-contact full-court strain measurement system,and mathematical model based on the propagation rule of rock stress wave,to obtain the dynamic strain distribution of the rock impacted by ASJ and explore the formation of the dynamic strain distribution.In the end,the study is carried out on the ASJ efficiency in rock breaking to master effects of the jet parameters on the rock-breaking efficiency,and to establish the prediction model of the rockbreaking efficiency.With the series of research works carried out,the main conclusions are achieved as follows.(1)The speed change of the slurry and the abrasive consists of three parts,which are the rapid accelerating in the nozzle contraction section,the steady acceleration in the nozzle linear part,and the slow deceleration in the air region.And the structure of ASJ consists of the convergent section,the transition section and the divergence section.Pressure is the most important factor of ASJ velocity,followed by target distance,while high-polymer concentration has the least influence on it.(2)There are four stress concentration areas in rock impacted by ASJ,which are the compressive stress concentration on rock surface at abrasive particle center,the tensile stress concentration on the rock surface at the edge of abrasive particle,the tensile stress concentration on the rock surface at the edge of the slurry jet,and the shear stress concentration at the particle axis under the rock surface.With increase of the velocity of the slurry jet and abrasive particles,the stress in the four regions increases gradually.And when the velocity is about 25m/s,the maximum shear stress will surpass the rock shear strength firstly,causing shear failure in the rock.Rock stress distribution around abrasive particle is dominated by the impact of abrasive particle,while rock stress distribution around slurry jet is dominated by the impact of slurry jet,which is caused by that the impact effect of abrasive particle decreases sharply with the increase of distance.(3)Dynamic stress distribution of rock broken by ASJ in spatial domain shows that stress concentration on the rock surface is propagated within the rock in the form of stress waves.And the stress decreases rapidly with the increase of distance.There is greater fluctuation in dynamic stress distribution of rock broken by ASJ in time domain,caused by rock stress be released instantaneously at the time of rock breaking,which also can prove rock breaking is stag-stepped.(4)The impact angle has significant influence on the width of the rock crater,while the impact time,angle and pressure have significant influence on the depth of the rock crater.The pressure,impact angle,time and high-polymer concentration are significant to the rock breaking efficiency based on the pit width,while the pressure,impact angle,and time are significant to the rock breaking efficiency based on the pit depth.A prediction model of rock-breaking efficiency is established to quantificat the effects of parameters on the rock-breaking efficiency.The conclusions can improve the mechanism of rock broken by ASJ,provide theoretical basis for safe and efficient mining of complex geological thin coal seam using ASJ united with cutting tool,which may promote the industrial application of abrasive jet technology in coal mining.In conclusion,the paper is of significant academic and practical value.