RS2 Features

Field Stress


The Field Stress option allows the user to define the in-situ field stress conditions prior to excavation. Two options are available for defining field stress in RS2 - Constant or Gravity field stress. Read more about each of the field stress options below: :

Constant
The Constant field stress option can be used for the modeling of deep excavations. In cases where the gravitational stress gradient is negligible across the height of your model, compared to the overall stress magnitude, a constant stress field is preferable. A Constant field stress is defined by two in-plane principal stresses (Sigma 1 and Sigma 3), and an angle which defines the in-plane stress orientation. The out-of-plane principal stress (Sigma Z) is also required.
Gravity
For surface or near-surface excavations, it is appropriate to use a Gravity stress field, in which the vertical stress is assumed to vary linearly with depth. The depth and the unit weight of overlying material determine the vertical stress distribution throughout the model. The horizontal stress is calculated by multiplying the vertical stress by the Horizontal/Vertical Stress Ratios.

The Use Actual Ground Surface option is very useful for surface excavations such as open pit mines, slopes, rock cuts etc. This method provides a better initial estimate of the vertical in-situ stress, for surface excavations where the ground surface is irregular (i.e. not defined by a single horizontal surface).
Custom
There are situations when you may need to specify the field stress for individual materials in a model, rather than a single field stress which applies to all materials.

For example, individual layers of material in bedded geological structures will sometimes have an in-situ stress that is different from the stress in surrounding layers. When this situation occurs, the user can define a customized field stress for any material(s) in their model.
Initial Element Loading
Initial Element Loading is specified in the Define Material Properties dialog, for each material. The Initial Element Loading option allows the user to specify whether Field Stress and/or Body Force is applied as the initial element loading, for each material:
  • If you are using Field Stress = Constant, then by default the Initial Element Loading for all materials will be Field Stress Only
  • If you are using Field Stress = Gravity, then by default the Initial Element Loading for all materials will be Field Stress & Body Force
  • You may also specify Initial Element Loading = Body Force Only (eg. for backfill materials). Or you may specify Initial Element Loading = None (no initial stress or force on the elements)

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