Ta-Ger¶

The Ta-Ger sand model. A critical-state model with a compact, physically interpretable parameter set. Unlike most other models here, its constructor ships with non-zero default parameter values (listed below), which provide a reasonable starting point. A Gmodel switch selects the shear-modulus formulation and Kw sets the pore-fluid stiffness.

At a glance

Class: ACT.models.ta_ger
numgeo name: Ta-Ger
Parameters with search bounds: 11
Imported as: from ACT.models import ta_ger

Default parameter values¶

Ta-Ger is instantiated with the following non-zero defaults, which serve as a starting point (override any of them with set):

Parameter	Default
`G0`	130
`m`	0.8
`nu`	0.15
`Q`	9.15
`R`	0.77
`emin`	0.597
`emax`	0.977
`phics`	32
`delta`	1
`kappa`	0.9
`Gmodel`	2
`Kw`	0.5e6

Default search bounds¶

These are the built-in lower/upper bounds used when a parameter is optimized. Override any of them with set_bounds.

Parameter	Lower	Upper	Description
`G0`	1.	10000.	shear-modulus constant
`m`	0.3	1.0
`nu`	0.0	0.45	Poisson's ratio
`Q`	8.0	11.0
`R`	0.25	1.50	size of the elastic / intergranular-strain locus
`emin`	0.2	1.2	minimum void ratio
`emax`	0.3	1.6	maximum void ratio
`phics`	25.0	42.0	critical-state friction angle (degrees)
`delta`	0.0	5.0
`kappa`	0.6	1.0
`Gmodel`	1.0	2.0	shear-modulus model switch (1 or 2)

Setting parameters¶

Assign initial / fixed parameter values with set(...):

from ACT.models import ta_ger

model = ta_ger()
model.set(G0=..., m=..., nu=..., Q=..., R=..., emin=...)

Full set signature

set(G0=None,m=None,nu=None,Q=None,R=None,emin=None,emax=None,phics=None,delta=None,kappa=None,Gmodel=None,Kw=None)

Available set parameters: G0, m, nu, Q, R, emin, emax, phics, delta, kappa, Gmodel, Kw.

Choosing free parameters¶

Narrow the search interval of selected parameters, then list the ones to optimize in globals.setup:

model.set_bounds(G0=[1., 10000.], m=[0.3, 1.0], nu=[0.0, 0.45], Q=[8.0, 11.0])
globals.setup(Model=model, Free_parameter=["G0", "m", "nu", "Q", "R", "emin"], ...)

Parameters that accept a set_bounds override: G0, m, nu, Q, R, emin, emax, phics, delta, kappa, Gmodel.

Reading & updating single parameters¶

model.update("G0", value)   # set one parameter
x = model.get_parameter("G0")  # read one parameter

See the models overview for the common interface shared by all models, and Optimization for how the free parameters are searched.