16.7. Kayenta Model

Note, many parameters of this model are undocumented.

BEGIN PARAMETERS FOR MODEL KAYENTA
  B0        = <real> b0
  B1        = <real> b1
  B2        = <real> b2
  B3        = <real> b3
  B4        = <real> b4
  G0        = <real> g0
  G1        = <real> g1
  G2        = <real> g2
  G3        = <real> g3
  G4        = <real> g4
  RJS       = <real> rjs
  RKS       = <real> rks
  RKN       = <real> rkn
  A1        = <real> a1
  A2        = <real> a2
  A3        = <real> a3
  A4        = <real> a4
  P0        = <real> p0
  P1        = <real> p1
  P2        = <real> p2
  P3        = <real> p3
  CR        = <real> cr
  RK        = <real> rk
  RN        = <real> rn
  HC        = <real> hc
  CTPSF     = <real> ctpsf
  CUTPS     = <real> cutps
  CUTI1     = <real> cuti1
  T1        = <real> t1
  T2        = <real> t2
  T3        = <real> t3
  T4        = <real> t4
  T5        = <real> t5
  T6        = <real> t6
  T7        = <real> t7
  J3TYPE    = <real> j3type
  A2PF      = <real> a2pf
  A4PF      = <real> a4pf
  CRPF      = <real> crpf
  RKPF      = <real> rkpf
  FAIL0     = <real> fail0
  FAIL1     = <real> fail1
  FAIL2     = <real> fail2
  FAIL3     = <real> fail3
  FAIL4     = <real> fail4
  FAIL5     = <real> fail5
  FAIL6     = <real> fail6
  FAIL7     = <real> fail7
  FAIL8     = <real> fail8
  FAIL9     = <real> fail9
  PEAKI1I   = <real> peaki1i
  STRENI    = <real> streni
  FSLOPEI   = <real> fslopei
  PEAKI1F   = <real> peaki1f
  STRENF    = <real> strenf
  FSLOPEF   = <real> fslopef
  SOFTENING = <real> softening
  IEOSID    = <real> ieosid
  DILATLIM  = <real> dilatlim
  NU        = <real> nu
  YSLOPEI   = <real> yslopei
  YSLOPEF   = <real> yslopef
  CKN01     = <real> ckn01
  VMAX1     = <real> vmax1
  SPACE1    = <real> space1
  SHRSTIFF1 = <real> shrstiff1
  CKN01     = <real> ckn02
  VMAX1     = <real> vmax2
  SPACE1    = <real> space2
  SHRSTIFF1 = <real> shrstiff2
  CKN01     = <real> ckn03
  VMAX1     = <real> vmax3
  SPACE1    = <real> space3
  SHRSTIFF1 = <real> shrstiff3
END [PARAMETERS FOR MODEL KAYENTA]

Kayenta is an outgrowth of the Brannon-Fossum-Strack isotropic geomaterial model that includes features and fitting functions appropriate to a broad class of materials including rocks, rock-like engineered materials (such as concretes and ceramics), and metals. Fundamentally, Kayenta is a computational framework for generalized plasticity models. As such, it includes a yield surface, but the term “yield” is generalized to include any form of inelastic material response including micro-crack growth and pore collapse. Kayenta supports optional anisotropic elasticity associated with ubiquitous joint sets. Kayenta supports optional deformation-induced anisotropy through kinematic hardening (in which the initially isotropic yield surface is permitted to translate in deviatoric stress space to model Bauschinger effects). The governing equations are otherwise isotropic. Because Kayenta is a unification and generalization of simpler models, it can be run using as few as 2 parameters (for linear elasticity) to as many as 40 material and control parameters in the exceptionally rare case when all features are used. Isotropic damage is modeled through loss of stiffness and strength. If ever you are unsure of the value of a parameter, leave it unspecified so that Kayenta can use an appropriate default. See [[1]] for a full description of the model, inputs, and output variables.

The command block for a Kayenta material starts with the line:

BEGIN PARAMETERS FOR MODEL KAYENTA

and terminates with the line:

END [PARAMETERS FOR MODEL KAYENTA]

In the above command blocks, the following are valid parameters for the Kayenta material model. If ever you are unsure of the value of a parameter, leave it unspecified so that Kayenta can use an appropriate default.

The initial elastic bulk modulus is defined with the B0 command line.
The high pressure coefficient in nonlinear elastic bulk modulus function is defined with the B1 command line.
The curvature parameter in nonlinear elastic bulk modulus function is defined with the B2 command line.
The coefficient in nonlinear elastic bulk modulus to allow for plastic softening is defined with the B3 command line.
The power in bulk modulus softening is defined with the B4 command line.
The initial elastic shear modulus is defined with the G0 command line.
The coefficient in shear modulus hardening is defined with the G1 command line.
The curvature parameter in shear modulus hardening is defined with the G2 command line.
The coefficient in shear modulus softening is defined with the G3 command line.
The power in shear modulus softening is defined with the G4 command line.
The joint spacing is defined with the RJS command line.
The joint shear stiffness is defined with the RKS command line.
The joint normal stiffness is defined with the RKN command line.
The constant term for meridional profile function of ultimate shear limit surface is defined with the A1 command line.
The curvature decay parameter in the meridional profile function is defined with the A2 command line.
The parameter in the meridional profile function is defined with the A3 command line.
The high-pressure slope parameter in meridional profile function is defined with the A4 command line.
One third of the elastic limit pressure parameter at onset of pore collapse is defined with the P0 command line.
One third of slope of porosity vs pressure crush curve at elastic limit is defined with the P1 command line.
The parameter for hydrostatic crush curve is defined with P2 command line.
The asymptote of the plastic volumetric strain for hydrostatic crush is defined with the P3 command line.
The parameter for porosity affecting shear strength is defined with the CR command line.
The triaxial extension strength to compression strengt ratio is defined with the RK command line.
The initial shear yield offset [non negative] is defined with the RN command line.
The kinematic hardening parameter is defined with the HC command line.
The tension cut-off value of I1 is defined with the CUTI1 command line.
The tension cut-off value of principal stress is defined with the CUTPS command line.
The relaxation time constant 1 is defined with the T1 command line.
The relaxation time constant 2 is defined with the T2 command line.
The parameter no longer in use. [set to zero] is defined with the T3 command line.
The parameter no longer in use. [set to zero] is defined with the T4 command line.
The relaxation time constant 5 (stress) is defined with the T5 command line.
The relaxation time constant 6 (time) is defined with the T6 command line.
The relaxation time constant 7 (1/stress) is defined with the T7 command line.
The type of 3rd deviatoric stress invariant function is defined with the J3TYPE command line.
The potential function parameter 1 (default=A2) is defined with the A2PF command line.
The potential function parameter 2 (default=A4) is defined with the A4PF command line.
The potential function parameter 3 (default=CR) is defined with the CRPF command line.
The potential function parameter 4 (default=RK) is defined with the RKPF command line.
The failed speed is defined with the FSPEED command line.
The peak I1 hydrostatic tension strength is defined with the PEAKI1I command line.
The peak (high pressure) shear strength is defined with the STRENI command line.
The initial slope of limit surface at PEAKI1I is defined with the FSLOPEI command line.
PEAKI1F is the same as PEAKI1I, but for failed limit surface.
STRENF is the same as STRENI, but for failed limit surface.
FSLOPEF is the same as FSLOPEI, but for failed limit surface.
The SOFTENING command line allows transition of limit surface from intact description to failed description.
The amount of time that passes with the stress state at the limit surface before the limit surface collapses (i.e., softens) is defined with the TFAIL command line.
The upper limit on plastic volume strain is defined with the DILATLIM command line.