New in Version 5.0

The "fast-flow" logic is extended in FLAC Version 5.0 to speed the calculation for both confined and unconfined fluid flow for conditions in which: (1) the bulk modulus of the fluid is large (or incompressible) compared to the drained modulus of the material; (2) there is a large contrast in permeability and/or porosity; or (3) there is a large variation in grid size. The new logic provides a substantial increase in calculation speed for both flow-only calculations and coupled mechanical flow calculations.

Formulations are generalized to incorporate the Biot coefficient of effective stress.

A new damping facility for dynamic calculations, hysteretic damping, is now available in FLAC Version 5.0. This form of damping allows strain-dependent modulus and damping functions to be incorporated directly into the FLAC simulation. This makes it possible for direct comparisons between calculations with the equivalent-linear method and a fully nonlinear model, without any compromises in the choice of constitutive model.

In addition, the need to introduce additional damping, such as Rayleigh damping, is greatly reduced and, consequently, the solution time is substantially reduced, by using hysteretic damping.

The Hoek-Brown failure criterion is implemented as a built-in constitutive model in FLAC 5.0. The failure surface is nonlinear and is based on the relation between the major and minor principal stresses. The model incorporates a plasticity flow rule that varies as a function of the confining stress level.

Three new structural element types have been added to FLAC 5.0:

• Liner Elements are similar to beam elements, but also include a failure criterion based on both bending stresses and axial thrust. Peak and residual strengths can be specified. Liner elements are well-suited to simulate concrete and shotcrete tunnel linings.
• Rockbolt Elements are similar to cable and pile elements, but also simulate: (1) tensile rupture of the element; (2) the effect of changes in the confining stress around the rockbolt; and (3) strain-softening of the material between the bolt and the grid material.
• Strip Elements represent the behavior of thin reinforcing strips installed in layers within a soil embankment. Strip elements have similar behavior to cable elements, but also simulate (1) tensile rupture, and (2) shear behavior at the soil/strip interface that is defined by a nonlinear shear failure envelope that varies as a function of confining stress.

New logic is available to install interfaces between beams or liners and the grid automatically, and also to install layers of beams and/or liners automatically.

The mechanisms of convective heat transfer (forced convection and free convection) in porous media are now provided with the thermal-analysis option in FLAC Version 5.0. Forced convection can be implemented with or without the fluid-flow configuration; in the latter case, fluid specific discharge is assigned as a property. Free convection is activated in FLAC zones containing the new isotropic advection/conduction model.

A network-key version of FLAC 5.0 is available. This version allows a single hardware key to be installed on a central (server) computer for a network. Individual users can then run FLAC from any computer(s) on the network. (The number of instances in which FLAC can be run is limited by the network key.) Network keys require a special licensing arrangement and installation. Contact Itasca for details.

A new FISH function, “FILTER.FIS,” is provided. This function filters an acceleration record to remove frequencies above a specified level.

New functions asin(a) and acos(a) are provided as FISH intrinsic functions to calculate the arc-sine and arc-cosine of a (result is in radians).

For dynamic analysis, grid variables x- and y-acceleration can be accessed from FISH using xacc and yacc.

For fluid-mechanical interaction analysis, the Biot coefficient may be accessed from FISH using the zone variable wbiot.

Five new examples have been added to the Example Applications manual volume:

• Example Application 14 — Dewatered Construction of a Braced Excavation
• Example Application 15 — Earthquake Loading of a Pile-Supported Wharf
• Example Application 16 — Pile-Supported Highway Embankment
• Example Application 17 — Lined Tunnel Construction in Saturated Ground
• Example Application 18 — Seismic Analysis of an Embankment Dam

Two new verification problems have been added to the Verification Problems volume:

• Verification Problem 20 — Slope Failure Due to Surcharge Load in Weightless Material
• Verification Problem 21 — Undrained Embankment Loading

Selected regions of the model can be excluded from the factor-of-safety calculation; Cable grout strength, friction and cohesion of the grout, can now be included in the FoS calculation.

Including: improvements to factor of safety analysis, plotting, access to model variables, interface removal, histories, structural element properties, and more.