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Laboratory tests

numgeo-ACT calibrates constitutive models against element tests — idealized laboratory experiments in which the stress and strain state is (assumed) homogeneous across the specimen. For every candidate parameter set, each selected test is reproduced by a numgeo element-test simulation and compared against your measured data.

This section describes the supported test types, what they measure, and how each one is simulated. The exact layout your data must follow in the Excel database is given on the Excel sheet reference page; here the focus is on the physics and the role each test plays in a calibration.

Supported tests

Test Loading Drainage Excel sheet Typical role in calibration
Oedometric compression monotonic drained OED-# stiffness under confined compression; controls compression parameters
Isotropic compression monotonic drained IC-# volumetric stiffness; limiting void-ratio / compression law
Drained triaxial (CD) monotonic drained CD-# shear strength & dilatancy at constant cell pressure
Undrained triaxial (CU) monotonic undrained CU-# effective stress path, undrained strength, pore-pressure build-up
Undrained cyclic triaxial cyclic undrained CUCYC-# cyclic mobility / liquefaction, pore-pressure accumulation
HCA — drained cyclic triaxial many cycles drained CDCYC_HCA-# strain accumulation under high-cyclic loading (HCA model)
HCA — undrained cyclic triaxial many cycles undrained CUCYC_HCA-# pore-pressure / strain accumulation under high-cyclic loading
Undrained cyclic simple shear cyclic undrained USScyc-# cyclic shear response, liquefaction in simple-shear conditions

You choose which tests to honour

A calibration uses whichever tests you pass to globals.setup. You can combine any subset — for example oedometer + drained + undrained triaxial for a monotonic calibration, or add cyclic triaxial tests to capture the cyclic response as well. Each test type is its own keyword argument (oedometer, triaxCD, triaxCU, triaxCUcyc, triaxCDcycHCA, triaxCUcycHCA, USScyc, iso_comp).

Monotonic vs. cyclic

The tests fall into two broad groups, and numgeo-ACT lets you balance them against each other through weighting:

  • Monotonic tests (oedometer, isotropic compression, drained/undrained triaxial) constrain the backbone response: stiffness, strength and dilatancy.
  • Cyclic tests (cyclic triaxial, cyclic simple shear, HCA) constrain the cyclic response: pore-pressure accumulation, cyclic mobility, liquefaction and — for the HCA model — long-term strain accumulation over many cycles.

By default, monotonic and cyclic groups each receive half of the total weight; this can be adjusted to emphasize the behaviour most relevant to your application.

How a test becomes a simulation

For every test in your database, numgeo-ACT:

  1. reads the initial state (void ratio, consolidation stresses, and for cyclic tests the loading amplitude and number of cycles) from the sheet;
  2. builds the corresponding numgeo element-test input;
  3. runs the simulation with the current parameter set (subject to a per-test timeout);
  4. extracts the same quantities you measured (e.g. stress–strain, stress path, pore pressure, accumulated strain) and compares simulation against experiment using the configured similarity measure.

The per-test scores are combined into the single objective value the optimizer minimizes.