Data Science

Data Interpretation: Isosurface Generation

An isosurface is a surface joining all points in space (within the region of available data) at which a given variable has the same value (referred to as the isovalue). For example, the s1 = 60 Mpa isosurface is the surface joining all points at which the variable s1 has a value of 60 Mpa. Users can easily generate isosurfaces in Examine 3D via the create isosurface option under the Volume Data menu. s1= 12 Mpa isosurface (highlighted green) of the a circular tunnel

Data Interpretation: Stress Trajectories When the trajectory is toggled on, cutting planes display direction information for vector variables; also, the direction indicators are colored to represent magnitudes, according to the Contour Legend. Users can choose between three stress trajectory shapes: strips (i.e., trajectory plates), arrows, or sticks. The arrows option gives a series of short arrow-plates oriented according to Table 3.1 (see User’s Guide). The sticks option converts the trajectories to lines oriented in the direction of the current principal stress component.

Major Principal Stress trajectories (arrows) around the neutrino observatory cavern

Data Interpretation: Stress Flow Ribbons

A trajectory ribbon is a tool for displaying the spatial variation of the three stress directions, all at the same time. It consists of a “ribbon” passed through selected points, such that its orientation represents the principal stress directions, as follows: the length dimension of the ribbon coincides with the direction of the maximum principal compressive stress (s1); the width dimension with the direction of the intermediate principal stress (s)2; and the normal to the ribbon coincides with the direction of the minimum compressive stress (s)3. In addition to showing the principal stress directions, trajectory ribbons are coloured to represent the magnitudes of the current stress component, according to the Contour Legend. They are treated like contours, and are thus operated on by any function that operates on contours.

Trajectory ribbons showing major principal stress flow (Mpa) around two excavations

Data Interpretation: Contours

The Interpret in Examine 3D allows users to better understand three-dimensional stress state around underground excavations through graphical representations of various contours. Presented below is a figure of the Interpret Menu. Users can plot various principal stresses, displacement and strength contours.

Interpret Menu

The figure below shows a sample strength factor contour. Similar analyses can be performed for stress and displacement.

Strength factor results around an underground powerhouse

Data Interpretation: Ubiquitous Joints

The Ubiquitous Joint option allows you to account for jointing in the surrounding rock by including joints in the strength factor calculations.When you select this option in the Interpret mode, a strength factor will be contoured, which accounts for the Ubiquitous Joint properties currently defined. As each stress location, the strength factor is calculated for the joint set using the Mohr-Coulomb or Barton-Bandis slip criterion properties you have entered.. The joint F.S. option will ignore the rock mass strength, and contour the strength factor for the ubiquitous joints only. The combined F.S option will contour the lesser of the ubiquitous joint strength or rock mass strength at each stress location.

Ubiquitous Joints menu

Data Interpretation: Advanced Rendering Capabilities

The Shade menu opens access to a set of functions for visualizing the over-all model, either shaded or in wire frame mode. Two of these functions, set color and shade options, are used to set values of parameters for the visualization. Computer graphics techniques such as transparency, shading and interactive rotation and movement of the model have been incorporated into the analysis tools so that the engineer can quickly visualize the three-dimensional nature of the geometry.

Display of the Shade menu, and four of its functions.

Set color

The set color function opens up a submenu which enables the users to assign different colors and transparency to objects.

A green isosurface with 100% transparency

A green isosurface with 62% transparency

Shade Options

The shade options sub-menu enables the user to control the appearance of, and the amount of information included in, shaded models. For example, users can specify between various lighting options: off, flat, gouraud and phong.

Default values for the parameters under the Shade options dialog

Animate

The animate function tumbles and rotates the perspective view window relative to the model, which has the appearance of tumbling and rotating the model (in the perspective window).

Quickshade

This function presents a shaded view of the model (see sample).

Data Interpretation: Seismic/General Data

Examine 3D has the ability to interpret seismic and general datas. The figure below is an example of a three-dimensional display of microseismic event locations located at the Falconbridge Lockerby mine in Sudbury. In this example, drift, shaft and ore pass geometry were incorporated from the Autocad mine geometry database for use in the visualization process. The actual stopes were taken from an Examine 3D stress analysis model. As seen in figure, the majority of the events occur in a pillar between the upper two stopes. The visualization of the temporal and spatial distribution pattern of the events provides important information for the determination of how the ore in this pillar might be mined. If a large number of events are currently occurring in the pillar, it is an indication that the rock is overstressed, and that rockbursting could accompany mining in this region. If current mining in the region around the pillar does not produce events within the pillar, it could mean that the rock has failed, resulting in a destressed zone within the pillar. It is unlikely that mining in this region would result in rockbursting. Field observation in this area could help in determining whether this is actually the case. Therefore, the pattern of propagation of the seismically active zones produces important information on yielded and overstressed regions within the rock mass.

Microseismic event locations at the Falconbridge Lockerby mine

Data Interpretation: Surface Excavation

The surface contours function plots values of stress at every node on the excavation surface. This allows the user to establish the state of stress right at the excavation/rock mass interface for the purpose of estimating instability.

Surface major principal stress (Mpa) contours

Data Interpretation: User Defined Functions

With this function, users can create contour plots of:

  1. any stress tensor component
  2. any displacement component
  3. write a mathematical expression containing these components, and view the results of this function.

 

For example, users can view a maximum shear surface contour as shown in the figure below:

Maximum shear surface contour of a pump house (Mpa)

Data Interpretation: Scattered Data Interpretation Examine 3D now has bundled with it a utility called eden3. Eden3 (not to be confused with eden or eden2) which is a utility that can take a set of discrete points in space, each point having an associated scalar value, and interpolate these values to some spatial function. It then maps this function to a regular grid, and generates a DAT file that can be viewed with the General option in the Interpret mode. The utility can also calculate event and energy densities. The utility can read in a variety of seismic format files (i.e. MP250, RDB etc.), along with a free format and Examine 3D formats that can be used by people with unsupported data files. Eden3 is completely menu driven and easy to use.

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