Irazu version 6.1 has launched and there are several new and exciting features that have been implemented including:
- the ability to import temporally varying and elevation-varying groundwater surfaces to apply hydrostatic fluid pressure;
- modelling the progressive deconfinement of an excavation using the force relaxation method; and
- the addition of help pages in the Irazu user interface.
Elevation-varying water table (Irazu 2D)
A new hydraulic boundary condition has been added to Irazu 2D Hydro, granting the capability to impose elevation-varying hydrostatic fluid pressures to a model. In addition, the water table can be temporally varied to simulate, for example, seasonal changes to the water table.
The new boundary condition is defined under the Boundary Conditions > Hydraulic tab. When Custom Hydrostatic Pressure is selected, a time-varying dialogue will pop-up and when you add an entry to the table you will be prompted to import CSV file(s). The selected CSV file(s) should contain the X-coordinates and Y-coordinates of the water table.
You have the option to import multiple water tables and set the time step at which they will be applied. By default, the imported water table will be assigned to all nodes in the model (Global Water Table is enabled). Upon successful import, Irazu will linearly interpolate the water table between the defined points of the water table. If the defined water table coordinates do not span the entire model, Irazu will extrapolate the water table horizontally past the extents of the model.
Force relaxation excavation method (Irazu 2D)
A new excavation method has been implemented in Irazu 2D that uses force relaxation to capture the gradual reduction of radial resistance around the excavation boundary to mimic 3D face effects. In the simulation, the core material is removed and replaced by relaxation forces that can be reduced over time using a relaxation factor between 1 (fully supported) and 0 (complete core removal). In addition, there is a modified version of the force relaxation method that allows a liner to be installed. In this instance, the liner material is temporarily removed from the simulation such that the unbalanced force can be computed, and then the liner is reintroduced into the simulation.
To use the force relaxation excavation method, go to the Excavations tab in Advanced Properties. Enable excavation for the tunnel core material and define the time step the material will be removed from the simulation. Finally, define the relaxation factor over time.
Help pages
Web-based help pages have been added to provide more information about specific features in Irazu. Throughout Irazu, look for the Help icon 
