# Spring Network Model Properties

The properties of the Spring Network Model are shown below for reference. More detailed information regarding these properties is presented in the model description.

Note

Some properties are read-only; these are indicated with *(r)* in the right margin.

- dp_force v
\(\mathbf{F^d}\) - dashpot force in units force. Expressed in the contact plane coordinate system.

- dp_mode i
\(M_d\) - dashpot mode with default value 0.

- dp_nratio f
\(\beta_n\) - normal critical damping ratio with default value 0.0.

- dp_sratio f
\(\beta_s\) - shear critical damping ratio with default value 0.0.

- emod f (r)
\(E^*\) - effective modulus in units force/area.

- fric f
\(\mu\) - friction coefficient with default value 0.0. If zero, \(\mu\) will be set if the bond friction angle \(\phi\) is specified.

- kn f
\(k_n\) - normal stiffness in units stress/disp/area, with default value 0.0.

- kratio f (r)
\(\kappa^*\) - normal-to-shear stiffness ratio.

- krot v
\(k_r\) - rotational stiffness in units stress/disp/area, with default value \(\mathbf{0}\). In 2D this is a floating point value.

- ks f
\(k_s\) - shear stiffness in units stress/disp/area, with default value 0.0.

- rgap f
\(g_r\) - reference gap in units length with default value 0.0.

- sn_area f (r)
\(A\) - area of the contact.

- sn_bmul f
\(\lambda_b\) - bending friction multiplier, with default value of 1.0.

- sn_coh f
\(\sigma_c\) - bond cohesive strength in units stress with default value 0.0.

- sn_cohdc f
critical slip distance (i.e., for degradation of shear strength as a function of slip) in units distance with default value 0.0.

- sn_cohtab v
cohesive strength multiplier (\(x\)-component) as a function of slip (\(y\)-component). Use sn_tabpos to set the table position when retrieving a value.

- sn_cohres f
residual cohesive strength in units stress with default value 0.0.

- sn_dil f
dilation angle in degrees with default value 0.0.

- sn_dilzero f
shear displacement where dilation stops in units distance with default value infinity.

- sn_fa f
\(\phi\) - bond friction angle in units degrees with default value 0.0. If specified and the friction coefficient \(\mu=0\) then it is set to this value.

- sn_force v
\(\mathbf{F}\) - linear force in units force with default value \(\mathbf{0}\). Expressed in the contact plane coordinate system.

- sn_heal i
healing mode with default value 0 (no healing). If set to 1 then the strength goes back to

`sn_coh`

when sliding ceases.

- sn_mcf f
\(\beta\) - moment-contribution factor with default value 1.0.

- sn_mode i
\(M_l\) - normal-force update mode with default value 0 (absolute update mode). Incremental normal-force update mode is set with \(M_l\) = 1. When the assign-stiffness, compute-stiffness, or bond methods are called, \(M_l\) is automatically set to 1.

- sn_moment v
\(\mathbf{M}\) - moment. Expressed in the contact plane coordinate system.

- sn_ndisp f
normal displacement in units distance with default value 0.0.

- sn_non_diag i
off-diagonal computation mode with default 0 (no off-diagonal Poisson correction). Off-diagonal terms are utilized when set to 1.

- sn_pois f
Poisson ratio with default value 0.0.

- sn_pois_force v (r)
Poisson force correction in units force. Expressed in the contact plane coordinate system.

- sn_porp f
\(P_p\) - Pore pressure in units stress. Positive pore pressure reduces the effective normal stress for failure computations.

- sn_radius (r)
\(\overline{R}\) - effective contact radius.

- sn_rmul f
\(\lambda\) - radius multiplier with default value 1.0.

- sn_sdisp v
accumulated shear displacement magnitude in units distance with default value \(\mathbf{0}\). The \(x\)-component is the accumulated shear displacement while slipping while the \(y\)-component is the sum of shear increments regardless of sliding state.

- sn_slip b (r)
\(s\) - slip state.

- sn_slipb b (r)
\(sn\) - bending slip state.

- sn_slipt b (r)
\(sn\) - twisting slip state.

- sn_shear f (r)
\(\tau_{c}\) - bond shear strength in units stress.

- sn_sigma f (r)
\(\sigma\) - bond normal stress at bond periphery in units stress.

- sn_state i (r)
\(B\) - bond state.

- sn_tabpos i
position in either the cohesion or tension table.

- sn_tau f (r)
\(\tau\) - bond shear stress at bond periphery in units stress.

- sn_ten f
\(\sigma_c\) - bond tensile strength in units stress with default value 0.0.

- sn_tendc f
critical tension distance (i.e., for degradation of tensile strength as a function of elongation) in units distance with default value 0.0.

- sn_tentab v
tensile strength multiplier (\(x\)-component) as a function of elongation (\(y\)-component). Use sn_tabpos to set the table position when retrieving a value.

- sn_tmul f
\(\lambda_t\) - twisting friction multiplier, with default value of 1.0.

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