RE: Modeling of Rock Bench Blasting in LS DYNA
James Kennedy
Dear Mohammad,
Three LS-DYNA discussions which might be considered helpful regarding feature inclusion in your modelling.
(1)
*MAT_096 (an anisotropic damage model) was employed in numerical simulations involving rock (granite) damage due to explosions:
Wei, X.Y., Zhao, Z.Y., and Gu, J., "Numerical Simulations of Rock Mass Damage Induced by Underground Explosion", International Journal of Rock Mechanics and Mining Sciences, Vol. 46, Issue 7, pp. 1206-1213, October, 2009.
The damage prediction of rock mass under blast loads induced by accidental explosions, rock bursts or weapon attacks is crucial in rock engineering. In this paper, parametric studies are conducted to evaluate the effect of loading density, rock mass rating (RMR) and weight of charge on the rock mass damage induced by underground explosions. The numerical simulations are carried out based on the transient dynamic finite element program ANSYS-LSDYNA. The numerical model was calibrated against the data obtained from a field blast test. A fully coupled numerical analysis, incorporating the explosion process, has been performed, where the large deformation zone near the charge is solved by the Arbitrary Lagrange–Euler (ALE) method. The deformable modulus and compressive strength of rock mass of granite are estimated by the RMR system. The peak particle velocity (PPV) damage criterion and the plastic strain criterion were adopted to study the damage zone around the charge hole, and an empirical formula considering the effects of loading density, RMR and weight of charge was obtained to estimate the damage zone in granite based on the numerical results.
https://www.sciencedirect.com/science/article/abs/pii/S1365160909000434
(2)
Several material models (*MAT_072R3, *MAT_105, *MAT_111, and *MAT_159) available in LS-DYNA, which would normally be useful to simulate a geo-material, were considered and investigated for rock cutting. Nevertheless, given that the rock cutting problem analyzed involved a series of complex breaking processes –including crack propagation and fragment separation–, it was imperative that the material model implemented lead to a robust simulation. *MAT_159, namely the Continuous Surface Cap Model, was chosen to fulfill this purpose:
Jaime, M.C., "Numerical Modeling of Rock Cutting and its Associated Fragmentation Process Using the Finite Element Method", Ph.D. Thesis, Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburg, Pennsylvania, November, 2011.
http://d-scholarship.pitt.edu/10611/1/Jaime_Maria_PhD_diss_ETD_Nov30_11.pdf
(3)
Blast Load Modeling
This introductory information was primarily taken from Slavik's presentation [2012] and the LS-DYNA User's Manual.
Blast simulations in LS-DYNA can be attempted by using a number of different available options. Among these are:
*LOAD_BRODE
Define an airblast (Brode) function for application of pressure loads due to a nuclear explosion.
The Brode model does not account for the angle of incidence of the blast wave on the surface of the structure.
*LOAD_BLAST
Define an airblast (CONWEP) function for the application of pressure loads from the detonation of conventional explosives.
The *LOAD_BLAST function calculates the pressure values by taking into account the angle of incidence of the blast wave.
Empirical pressure loads applied directly to the nodes of a Lagrangian structure.
*LOAD_BLAST_ENHANCED
Define an airblast (CONWEP) function for the application of pressure loads due the detonation of a conventional explosive.
While similar to *LOAD_BLAST this feature includes enhancements for treating ground reflected (Mach Stem) waves, moving warheads and multiple blast sources.
Multi-Material Arbitrary Lagrangian Eulerian (MM-ALE) method.
Explicit modeling of explosive and air using equations-of-state.
Lagrangian structure is loaded using Fluid Structure Interaction.
A hybrid combination of above options.
Coupling of empirical airblast loads (CONWEP) to ALE air domains.
*LOAD_BLAST_ENHANCED coupled with the Multi-Material Arbitrary Lagrange Eulerian (MM-ALE).
Particle method.
Smooth Particle Hydrodynamics (SPH) coupled with classical Lagrangian structural analysis.
*INITIAL_IMPULSE_MINE
An engineering model based on experimental results, much like the airblast engineering model provided by *LOAD_BLAST_ENHANCED.
Based on the work of Westine, et al. [1985] as presented, and extended, by Tremblay [1998]. The implementation is applicable to flat (horizontal) and oblique (angled) target plates consisting of either shell or solid elements.
Applies initial velocities to the nodes of a structure due to the impulse imparted by the detonation of a buried land mine.
*PARTICLE_BLAST
Modeled by real gases: p(V-b) = nRT.
The co-volume effect is included.
Works for high pressure and high temperature.
Pressure drops sharply during adiabatic expansion.
reference
Slavik, T.P., "Blast Loading in LS-DYNA", Livermore Software Technology Corporation, Livermore, California, May, 2012.
http://ftp.lstc.com/anonymous/outgoing/support/PRESENTATIONS/blast_slavik_ucsd.pdf
Sincerely,
James M. Kennedy
KBS2 Inc.
January 25, 2024
From: ls-pr...@googlegroups.com [mailto:ls-pr...@googlegroups.com]
On Behalf Of Mohammad Ashikur Rahman
Sent: Thursday, January 25, 2024 10:14 AM
To: ls-pr...@googlegroups.com
Subject: Modeling of Rock Bench Blasting in LS DYNA
Hello everyone.
I am a postgraduate (Master) student, trying to model blasting of rock mass using LS DYNA. Though I have prepared a model it is not running. I learned some parts of it from different mediums as well as my supervisor helped me and now I
want to take it forward. I seek your guidance in this regard. I humbly expect your cooperation and it will be highly appreciated.
Sincerely,
Mohammad Ashikur Rahman
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James Kennedy
Dear Mohammad,
Some additional presentations, primarily Swedish research, that may be of some interest:
Using blasting caps with electronic delay units, it has become possible to employ wave superposition in rock blasting. This paper presented computer simulations to investigate the hypothesis that fragmentation was improved in areas between blast holes where the tensile waves meet, overlap and interact. In this study, a numerical methodology using the code LS-DYNA was developed. Two different element formulations were used — Euler formulation in, and close to, the blast hole, and Lagrange formulation in the rock volume farther from the blast hole. A methodology to calculate possible fragmentation based on model interpretation was developed:
Sjoberg, J., Schill, M., Hilding, D., Yi, C., Nyberg, U., and Johansson, "Computer Simulation of Blasting with Precise Initiation", Eurock 2012: Rock Engineering and Technology for Sustainable Underground Construction, Stockholm, Sweden, May, 2012.
http://pure.ltu.se/portal/files/36979526/171P_Sjoberg_Computer_Simulation_Blasting.pdf
Schill, M., “Finite Element Simulations of Blasting and the Effects of Precise Initiation on Fragmentation”, Swebrec Report, No.2012:2.
https://www.dynalook.com/conferences/12th-international-ls-dyna-conference/blast-impact13-a.pdf
A series of numerical simulations of rock blasting has been conducted using the LSDYNA software in order to test the hypothesis proposed by Rossmanith, stating that interaction of stress waves could result in finer fragmentation by controlling the initiation times. The rock material was simulated with the RHT material model. After the calculation, the elements with damage level above 0.6 were removed to simulate complete fracturing of the rock.
Yi, C., “Improved Blasting Results with Precise Initiation – Numerical Simulation of Small-scale Tests and Full-scale Bench Blasting”, Swebrec Report, No.2013:2.
https://www.diva-portal.org/smash/get/diva2:996262/FULLTEXT01.pdf
It is difficult for a conventional continuum-based approach such as the finite element method (FEM) to model the rock fragmentation by blasting and the expansion work on the rock by explosive and its detonation products. In this paper, the particle blast method (PBM) was employed to model the behaviour of the detonation and a bonded particle model (BPM) was used to model the brittle material to be blasted. The blast process from crack initiation to fragment formation was analyzed:
Yi, C., and Johansson, D., "Discrete Element Modelling of Blast Fragmentation of a Mortar Cylinder", 11th International Symposium of Rock Fragmentation by Blasting, Sydney, Australia, August, 2015.
http://www.fragblast11.org/Media/Fragblast11/presentations/SESSION_10A_1150.pdf
Sincerely,
James M. Kennedy
KBS2 Inc.
January 29, 2024