Please see the website www.geomaterialmodeling.com. Also see http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/civil_engineering_powerpoint_from_ARUP.pdf _______________________________________________________________________________________________ RE: Modeling approaches that may be applicable to simulation of soil impact Several solution methods are available for modeling the soil in your [impact] application. In all cases, the main challenge will likely involve deriving input data for the constitutive model. 1) Lagrangian finite elements, or the Element Free Galerkin method, with material erosion and/or mesh adaptivity. 2) Arbirtary Lagrangian-Eulerian (ALE) method. http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/penetrator_vs_ale_mat5soil.k.gz http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/penetrator_vs_ale_mat16soil.k.gz are examples of penetration into an ALE soil target. 3) Smooth Particle Hydrodynamics (SPH) method. http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/concrete/JXu-rigid_ball_into_sph_concrete.zip is an example of penetration into an SPH concrete target. 4) Discrete Element Sphere (DES) method with element bonds. Development of the bond model (*DEFINE_DE_BOND) will require a heuristic approach with lots of trail and error simulations paving its way. 5) A hybrid approach with *DEFINE_ADAPTIVE_SOLID_TO_SPH or *DEFINE_ADAPTIVE_SOLID_TO_DES. With those features we begin with solid Lagrangian elements, and as those solids fail and are deleted, they are replaced with SPH (or DEM) particles. So, mass is conserved, and the calculation continues with particles representing the failed material. (Based on ts's Ticket#2018021410000043) _______________________________________________________________________________________________ RE: Material models in LS-DYNA which may be suitable for modeling soil mat 1: mat_elastic If deformation is small as in some drop impacts, soil behavior might be reasonably assumed to be linear. mat 5: mat_soil_and_foam A very simple model with a pressure-dependent yield surface and a tensile cutoff. Should generally not be used if material is not confined. Often used for penetration analyses. Some sample material constants (pedigree and type of soil unknown) are as follows: *MAT_SOIL_AND_FOAM $ English units: in, s, snails, psi $ rho G K A0 A1 A2 PC 1,1.589E-04,6.170E+05,1.110E+06,0.000E+00,0.000E+00,8.500E-02, -1. $ pressure cutoff may have to be set high if Euler/ALE formulation used 0.000E+00 $ ln(V/V0) 0.000E+00,-5.600E-02,-0.100,-0.151,-0.192 $ pressure 0.000E+00,2.000E+03,3.200E+03,6.240E+03,1.060E+04 $ end For an example of a projectile penetrating soil (soil modeling using Eulerian elements), see http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/penetrator_vs_ale_mat5soil.k.gz mat 14: mat_soil_and_foam_failure Like mat 5 but will not carry tension after pressure cutoff is reached. *MAT_SOIL_AND_FOAM_FAILURE $ Courtesy of Ala Tabiei $ Antelope Lake Soil, Nevada, mm,ton,sec,N,N/mm^2 $ very stiff silty clay over dense sand with occasinally gravel sand $# mid ro g bulk a0 a1 a2 pc 1 1.8740E-9 358.54999 1523.8199 0.158000 0.124000 0.024000 -0.150000 $# vcr ref 0.000 0.000 $# eps1 eps2 eps3 eps4 eps5 eps6 eps7 eps8 0.000 -0.073000 -0.134000 -0.191000 -0.263000 -0.313000 -0.333000 -0.390000 $# eps9 eps10 -0.460000 $# p1 p2 p3 p4 p5 p6 p7 p8 0.000 0.300000 1.200000 2.500000 4.990000 9.030000 15.030000 40.000000 $# p9 p10 70.000000 mat 16: pseudo_TENSOR Includes an option for a Mohr-Coulomb failure surface. For an example of a projectile penetrating soil (soil modeling using Eulerian elements), see http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/penetrator_vs_ale_mat16soil.k.gz mat 25: mat_geologic_cap_model Limited to two stress invariants (J2 and J1) so it can't represent the well known behavior of rocks & concrete that they are weaker in triaxial extension (TXE) then in triaxial compression (TXC). To consider this, you need a 3-invariant model that includes J3. A three invariant, smooth cap model developed by Schwer and Murray is available in version 970 (mat 145). mat 78: mat_soil_concrete mat 79: mat_hysteretic_soil Richard Sturt 18-may-10 New capability for MAT_HYSTERETIC_SOIL - can input desired friction angle, the yield surface is then scaled to achieve a quasi-Mohr-Coulomb yield behaviour. Richard Sturt 6-may-10 Add strain rate effect to MAT_079. mat 80: mat_ramberg-osgood Simple shear behavior of soils for seismic analysis (empirical and assumes deviatoric stresses are uncoupled; pressure is elastic. Energy dissipation through hysteretic behavior. The following 3 models were developed or co-developed by Aptek (contact is Yvonne Murray, yvonne@aptek.com). mat 145 mat_schwer_murray_cap_model A three invariant, smooth cap model mat 147 mat_fhwa_soil, mat_fhwa_soil_nebraska Brett Lewis' soil model 147 reports are available electronically: http://www.tfhrc.gov/safety/pubs/04095/04095.pdf or http://www.tfhrc.gov/safety/pubs/04095/index.htm http://www.tfhrc.gov/safety/pubs/04094/04094.pdf or http://www.tfhrc.gov/safety/pubs/04094/index.htm mat 159 mat_cscm A Continuous Surface geologic Cap Model that is primarily an enhanced mat 145. Both models use roughly the same smooth cap three-invariant plasticity surface and a viscoplastic formulation for strength enhancement at high strain rates. But the isotropic damage formulation was enhanced in mat 159 to do a better job of modeling blast loaded reinforced concrete columns that fail in shear, and for concrete structures impacted by vehicles (roadside safety). So I would expect MAT 159 to do a better job of modeling damage in concrete. mat 145 has two features not available in MAT 159: - An explicit pore collapse model with an Mie Gruneisen Equation of State for modeling nonlinear pressure-volumetric strain based on Rankine-Hugoniot relationships. I previously used this formulation for modeling soil compaction in the vicinity of an explosive. - A scalar anisotropic damage model, which was evaluated for modeling rock. I believe, but I am not certain, that this anisotropic model was implemented into the LS-DYNA version. The following three models were implemented by Ove Arup (brian.walker@arup.com): mat 173: mat_mohr_coulomb (Release 3 of v. 971) For sandy soils and other granular materials. mat 192: mat_soil_brick mat 193: mat_drucker_prager mat 232: mat_biot_hysteretic to be used for modeling the nearly-frequency-independent viscoelastic behaviour of soils subjected to cyclic loading, e.g. in soil-structure interaction analysis Sand: Sand typically has zero cohesion. Cohesionless sand can be modeled using mat_173 (*mat_mohr-colomb) or *mat_016's Mohr-Coulomb yield surface option. Lagrangian solids or SPH can be used with either material model. An alternative method, only recently added, for treatment of granular materials is the DEM (Discrete Element Method). See these commands... *ELEMENT_DISCRETE_SPHERE *CONTROL_DISCRETE_ELEMENT *DEFINE_DE_TO_SURFACE_COUPLING *DEFINE_DE_ACTIVE_REGION ___________________________________________________________________ RE: Pore pressure Soil models which include some consideration of pore pressure as an option are: mat_145 (developed by Len Schwer, Len@Schwer.net) mat_147 (developed by Yvonne Murray, yvonne@aptek.com) mat_159 mat_16 with eos_11 (*eos_tensor_pore_collapse) In addition, pore pressure can be added to any material using the PWP family of commands ... *boundary_pwp *boundary_pore_fluid *control_pore_fluid *database_pwp_flow *database_pwp_output *initial_pwp_depth *mat_add_permeability *load_added_pwp See p. 65 of http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/BWalker_Jan2008.pdf for a brief illustration of this pore pressure capability. Examples are provided in http://ftp.lstc.com/anonymous/outgoing/support/FAQ_kw/soil/arup_qa.tar.gz Question: (1) Drained and Undrained loading conditions via LS-DYNA. When saturated coarse-grained soils (sand and gravel) are loaded slowly, volume changes occur, resulting in excess pore pressures that dissipate rapidly, due to high permeability. This is called drained loading. On the other hand, when fine-grained soils are loaded, they generate excess pore pressures that remain entrapped inside the pores because these soils have very low permeabilities. This is called undrained loading. In case of triaxial compression test, how can I simulate undrained and drained loading conditions? Is there some options for these loading conditions in LS-DYNA? (2) Mat25 In case to define Mat25 material parameters, should I have to determine drained strength parameters? If drained strength parameters should be defined in Mat25, how can I simulate undrained loading conditions? Answer from Richard Sturt of Arup, 11/18/09 (to Yahoo group): You can simulate drained and undrained conditions using *CONTROL_PORE_FLUID and *BOUNDARY_PORE_FLUID in LS971 R4.2.1. There are other pore-pressure related keywords too. These are not in the printed 971 keyword manual (the green book dated 2007) but they are in recent electronic LS971 manuals. When you use these keywords, the *MAT parameters define the effective stress behaviour (using Terzaghi's concept of effective stress). The same *MAT parameters can be used for both drained and undrained loading. I uploaded a file today to the group's "Files" area. Look for undrained_1el.key. http://groups-beta.google.com/group/LS-PrePost Group email: LS-PrePost@googlegroups.com >I was wondering whether the LSDYNA is capable of analyzing the cyclic >response behavior of the soil material under an impact loading. This can >be a problem that can occur where the saturated soil is supported by a >certain kind of coastal structure. The instant pore water pressure >generation as well as the shear stress-strain properties of the soil in >this kind of situation is particularly important. As far as the soil >material, I know that LSDYNA has a lot of different material types for >that but I don't know if this type of study could be handled. ____________________________________________________________________________ RE: Some references pertaining to soil modeling Following from JK in LSPP User Group in response to request for material properties for sand (wet and dry), 2/8/17: *MAT_005 (data included) was used to present the constitutive material models for one soil, unwashed sand, from NASA Langley's gantry drop test facility and three soils from Kennedy Space Center: Thomas, M.A., Chitty, D.E., Gildea, M.L., and T'Kindt, C.M., "Constitutive Soil Properties for Unwashed Sand and Kennedy Space Center", NASA CR-2008-215334, National Aeronautics and Space Administration, Langley Research Center, Hampton, Virginia July, 2008. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080032551_2008032903.pdf *MAT_005 (data included) and *MAT_063 were used to represent soft soil and unwashed sand in drop simulations: Fasanella, E.L., Lyle, K.H., and Jackson, K.E., "Developing Soil Models for Dynamic Impact Simulations", 65th International American Helicopter Society Forum, Grapevine, Texas, May, 2009. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090022374_2009022165.pdf *MAT_147 was applied to evaluate the liquefaction potential of saturated sandy soil subjected to sequential blast environments: Lee, W.Y., "Numerical Modeling of Blast-Induced Liquefaction", Ph.D. Thesis, Civil and Environmental Engineering, Brigham Young University, Provo, Utah, August, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1431.pdf *MAT_005 and *MAT_063 (data included) were used to represent unpacked sand in a drop simulation: Fasanella, E.L., Jackson, K.E., and Kellas, S., "Soft Soil Impact Testing and Simulation of Aerospace Structures", 10th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2008. http://www.dynalook.com/international-conf-2008/SimulationTechnology5-2.pdf http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20080022954_2008021652.pdf *MAT_193 (main input parameters of the material model are included) was employed to represent the soil in numerical simulations of direct shear tests: Barrios, D.O.S., "Determination of Soil Properties for Sandy Soils and Road Base at Riverside Campus Using Laboratory Testing and Numerical Simulation", Master's Thesis, Department of Civil Engineering, Texas A&M University, College Station, Texas, May, 2010. http://repository.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-2010-05-8042/SAEZ-BARRIOS-THESIS.pdf *MAT_005 (data included) model was employed to simulate riverbed soil (silty clay sand) that surrounds piers in bridge design: Bojanowski, C., and Kulak, R.F., "Comparison of Lagrangian, SPH and MM-ALE Approaches for Modeling Large Deformations in Soil", 11th International LS-DYNA Users Conference, Dearborn, Michigan, June, 2010. http://www.dynalook.com/international-conf-2010/Simulation-4-5.pdf The soil material was modeled using *MAT_005 to simulate a Norfolk sandy loam (data included): Kulak, R.F., and Bojanowski, C., "Modeling of Cone Penetration Test Using SPH and MM-ALE Approaches", 8th European LS-DYNA Conference, Strasbourg, France, May, 2011. http://www.dynalook.com/8th-european-ls-dyna-conference/session-21/Session21_Paper2.pdf *MAT_005 (data included) was used to represent dry sand and sandy loam soils for this thesis study. Given the dependency of the sandy loam's resistance to penetration on the rate of loading, *MAT_016 (data included) was considered as an alternative numerical model: Wright, A., "Tyre/Soil Interaction Modelling within a Virtual Proving Ground Envir- onment", Ph.D. Thesis, School of Applied Sciences, Cranfield University, Cranfield, United Kingdom, January, 2012. https://dspace.lib.cranfield.ac.uk/handle/1826/7904/A_Wright_Thesis_2012.pdf *MAT_014 (six sets of data included) was chosen to perform the finite element simulation of the dynamic compaction (DC) tests (sand-silt models) for this work. The FE simulations conducted were limited to the Lagrangian approach. Preliminary simulations were reproduced using the ALE approach for comparison and sensitivity analysis: Nazhat, Y., "Behaviour of Sandy Soil Subjected to Dynamic Loading", Ph.D. Thesis, School of Civil Engineering, University of Sydney, Sydney, New South Wales, Australia, May, 2013. http://ses.library.usyd.edu.au/bitstream/2123/9435/1/Nazhat_Y_thesis.pdf http://ses.library.usyd.edu.au/handle/2123/9435