Detonation Velocity Data Research Articles

A Non-Ideal Detonation Model for Evaluating the Performance of Explosives in Rock Blasting

A new model to predict the non-ideal detonation behaviour of commercial explosives in rock blasting is presented. The model combines the slightly divergent flow theory, polytropic equation of state, simple pressure-dependent rate law and statistical expressions to model the effect of confinement on detonation. The model has been designated as DeNE, an acronym for the Detonics of Non-ideal Explosives. It is aimed at predicting the detonation state and subsequent rarefaction (Taylor) wave to provide the pressure history for different explosive, rock type and blasthole diameter combinations. It enables the prediction and comparison of the performance of commercial explosives in different blasting environments. The unconfined detonation velocity data has been obtained from the testing of six commercial explosives to calibrate DeNE. A detailed sensitivity analysis has been conducted to evaluate the model. The model has been validated using the results of hydrocodes as well as measured and published in-hole detonation velocity data.

Prediction of the non-ideal detonation performance of commercial explosives using the DeNE and JWL++ codes

SUMMARY The non-ideal detonation performance of two commercial explosives is determined using the DeNE and JWL++ codes. These two codes differ in that DeNE is based on a pseudo-one-dimensional theory which is valid on the central stream-tube and capable of predicting the non-ideal detonation characteristics of commercial explosives as a function of the explosive type, rock properties and blasthole diameter. On the other hand, JWL++ is a hydrocode running in a 2-D arbitrary Lagrangian– Eulerian code with CALE-like properties and can determine the flow properties in all stream lines within the reaction zone. The key flow properties (detonation velocity, pressure, specific volume, extent of reaction and reaction zone length) at the sonic locus on the charge axis have been compared. In general, it is shown that the flow parameters determined using both codes agree well. The pressure contours determined using the JWL++ are analysed in detail for two explosives at 165 mm blastholes confined in limestone and kimberlite with a view to further investigate the explosive/rock interface. The DeNE and JWL++ codes have been validated using the measured in-hole detonation velocity data. Copyright 2005 John Wiley & Sons, Ltd.

A Statistical Approach to Predict the Effect of Confinement on the Detonation Velocity of Commercial Explosives

Commercial explosives behave non-ideally in rock blasting. A direct and convenient measure of non-ideality is the detonation velocity. In this study, an alternative model fitted to experimental unconfined detonation velocity data is proposed and the effect of confinement on the detonation velocity is modelled. Unconfined data of several explosives showing various levels of non-ideality were successfully modelled. The effect of confinement on detonation velocity was modelled empirically based on field detonation velocity measurements. Confined detonation velocity is a function of the ideal detonation velocity, unconfined detonation velocity at a given blasthole diameter and rock stiffness. For a given explosive and charge diameter, as confinement increases detonation velocity increases. The confinement model is implemented in a simple engineering based non-ideal detonation model. A number of simulations are carried out and analysed to predict the explosive performance parameters for the adopted blasting conditions.

Equation of state for detonation product gases

A thermodynamic analysis procedure of the detonation product equation of state (EOS) together with the experimental data set of the detonation velocity as a function of initial density has been formulated. The Chapman–Jouguet (CJ) state [W. Ficket and W. C. Davis, Detonation: Theory and Experiment (University of California Press, Berkeley 1979)] on the p-ν plane is found to be well approximated by the envelope function formed by the collection of Rayleigh lines with many different initial density states. The Jones–Stanyukovich–Manson relation [W. Ficket and W. C. Davis, Detonation: Theory and Experiment (University of California Press, Berkeley, 1979)] is used to estimate the error included in this approximation. Based on this analysis, a simplified integration method to calculate the Grüneisen parameter along the CJ state curve with different initial densities utilizing the cylinder expansion data has been presented. The procedure gives a simple way of obtaining the EOS function, compatible with the detonation velocity data. Theoretical analysis has been performed for the precision of the estimated EOS function. EOS of the pentaerithrytoltetranitrate explosive is calculated and compared with some of the experimental data such as CJ pressure data and cylinder expansion data.

Helium dilution for ram accelerator operation

Experimental detonation characteristics (detonability limits and detonation velocities) of methane-oxygen-helium mixtures at initial pressures of up to 5 MPa were measured in a 90 mm caliber, 11.7 m long (130 calibers) smooth-bore detonation tube. Stoichiometric as well as fuel-rich mixtures were investigated in order to provide performance data for ram accelerator applications. The experimental results were used to adjust and validate calculations of the Chapman-Jouguet detonation characteristics by means of a thermochemical code based on various real gas equations of state. On the basis of the detonation velocity data, a series of intermolecular parameters involved in the thermochemical code was determined. Furthermore, the investigation enabled to determine of the upper detonable area of these dense ternary mixtures under the present experimental conditions.

Detonation properties of dense methane-oxygen-diluent gaseous mixtures: application to ram accelerators

Using a 90mm-bore, 3.15 m long detonation tube, experimental detonation characteristics (detonability limits, detonation velocities and peak pressures) of stoichiometric methane-oxygen-diluent mixtures at an initial pressure up to 3.5 MPa have been experimentally investigated. A parametric study has been carried out as a function of both amount and nature of diluent, namely carbon dioxide, nitrogen and helium. The experimental results allowed the adjustment and validation of computations of the Chapman-Jouguet characteristics by means of a thermochemical code. These experimental data associated with validated computations provide a valuable tool, among others, for the choice of the most appropriate mixture composition in the superdetonative combustion mode for ram accelerator (ramac) experiments. The investigations were organized to determine the upper detonable areas of dense ternary mixtures, and to provide detonation velocity data in order to adjust a series of intermolecular parameters involved in the thermochemical code.

Predicting High Explosive Detonation Velocities from their composition and structure (II)

AbstractAn earlier paper(1) described a simple linear relationship between detonation velocity of 64 ideal C,H,N,O type explosives at their theoretical maximum densities (TMD's) and a factor. F, that is dependent solely upon chemical composition and structure. Based upon available experimental data for nine fluorine‐containing explosives, the equation for calculating the factor has been expanded to include compositional terms for fluorinated compounds. In addition, the reliability of the linear relationship has been further tested against seven more recently published C,H,N,O type explosive experimental detonation velocity data points. The calculated detonation velocity values for all 16 explosives lie within 6.0% of experimental with an absolute error of ± 3.0%.

Comments on the equation of state of the products of high density explosives

The problem of the thermal equation of state of the products of solid explosives is considered. It is assumed that the products are in chemical equilibrium, that the specific chemical heat released is independent of the loading density, and that the detonation density is proportional to the loading density. Using the energy conservation equation and thermodynamic relationships, it is then shown that the thermal equation of state must satisfy the following relationship: F [ T ( 1 − K ) / 2 K υ ; υ ( 1 + K ) / ( 1 − K ) p ] = 0 . where K is a constant and F is an arbitrary function of its two arguments. It is then argued that the experimental knowledge of detonation velocity, pressure, density, and particle velocity versus loading density is not enough to check the validity of an assumed thermal equation of state of the products and to compute the detonation temperature. In particular, it is explained why similar detonation pressures, densities, and particle velocities, but completely different detonation temperatures have been calculated by various authors, using similar detonation velocity data but different thermal equations of state.

Precision Measurement of Detonation Velocities in Liquid and Solid Explosives

A versatile chronographic technique for the measurement of detonation velocities in liquid and solid explosives is discussed. A raster-type oscilloscope is described which has a sweep linearity of 1% and a time coverage of 300 μsec. This instrument is composed of standard electronic components and requires relatively little maintenance. The basic signal mixing circuits used to generate fast-rising pulses associated with the detonation of an explosive charge are briefly described. Some electrical effects associated with the detonation of an explosive charge are briefly described to point out a possible source of spurious signals. Techniques for the preparation and assembly of explosive charges are presented together with certain precautions which must be taken against the possibility of the generation of false signals. The effect of temperature on detonation velocities of liquid and solid explosives is mentioned. Using the techniques and precautions described, it is possible to obtain detonation velocity data with a precision of 0.1% or better.