Mechanism And Experimental Study On Rock Splitting Under Shaped Charge Jet Penetrate

Based on the goal of efficiently and safely splitting huge rocks and dangerous stones,the author has advanced a new method of directionally splitting huge rocks and exploredthe controlled theory of splitting situation via using penetration of linear shaped charge.Rock fracturing mechanism have studied by the comprehensive methods whichcombine with theoretical research, the model test, High-speed3D DIC test, numericalsimulation and engineering practice. The main research contents and conclusions are asfollows:(1) The paper has studied the dynamic response features of huge rock under thepenetration of linear shaped charge. The research reveals that: Crack shape of huge rock inthe dynamic response determines the splitting crack propagation path and the radial crackpropagation mode. Based on gap theory the author deduced the critical stress condition ofthe crack initiation and the necessary condition under stress wave.Meanwhile, the tensilestress concentration effect of penetration cracks at extending direction of crack position andthe initial control function is analyzed.(2) The author has conducted model test which selects the beneficial height of burstamong different charges. The result shows: when wedge vertex angle is45°, the sampleforms the crack at single principle plate along axial direction of shaped charge. When thewedge vertex angle is60°, the sample forms symmetrically radical split in centre. When thewedge vertex angle is90°, the sample crushes and the fragmentation is symmetricalbetween both sides of axial direction of penetration. At the same linear shaped charge,conical fracture can be controlled via decreasing the ratio of height to diameter.(3) Combined with the technology of high-speed photography, build a High-speed3DDIC （High speed3D digital image correlation method）test platform, it is the first time toaccomplish the non-contact full strain measurement on diametral compression test underthe action of energy-gathered by explosion,the test results show that the penetration axialplane always locate the principal tensile strain concentration belt, principal strainconcentration belt shape and distribution position determines the crack propagation pathand trend, the speed of peak splitting crack propagation is221.81m/s, the average speed is 84.47m/s; the strain rate on the test surface is under102orders of magnitude, the quasistatic fracturing pattern in specimen.(4) Research the numerical simulation based on model test results, the results showsthat: Both decrease the wedge vertex Angle of the charging structure with and increase ofthe linear length can improve the penetration strength which concentrate shaped charge tothe axial principal plane, the dynamic stress ratio of major axis to minor axis in initial crackcontrol direction and number of crack, and the dynamic stress ratio of axial principal planeto its orthogonal radial principal plane determines the specimen crack propagation modeland eventually split form. Though fitting formula about the plane stress peak on1/2mainsplitting plane stress to calculate the limit size, cleavage plane of charge structure thematching relationship between the size of the specimen is optimized.(5) Analysis of dynamic stress load spectrum characteristics influence on cleavagecrack propagation speed, the results show that under the condition of stress field intensitydecrease, stress wave only can make the cracks with the increase of the low frequencycomponent in local accelerated expansion. Based on spherical fragments expansion brokenmodel, can use penetration effect to adjust specimen internal stress wave energy density anddistribution of activated defect density for control of the broken blocks.(6) At the scene of the mine production, the use of linear shaped charge split play toachieve the control in the form of heterogeneous mass of rock fracturing. Fill in0.5Kgemulsion explosive, analysis of the explosion shock wave over pressure distribution, theresults show that：through use explosion-proof blanket of splitting and protect chunks rock,shock wave peak dropped by about90%, blasting flying objects is completely covered,inside the large mechanical equipment use ensures the mechanical parts from beingdamaged.