PLAXIS: Numerical Analysis for Hard-Rock Pillars

One aspect rarely considered in the analysis of hard rock pillars, and indirectly in synthetic rock mass models to determine rock mass strength, is the actual stress level and stress path imposed on the pillar due to the excavation sequence and the location of the pillars within the mine layout. Read this article to explore how by comparing 3D and 2D results for selected cross sections across, you can gain insights about the stability implications of a 2D approach to pillar design and synthetic rock mass modeling.

Stress Level Impact on Rock Pillars 

Rock pillars can be defined as the in-situ rock between two or more underground openings. However, one aspect that is seldom considered in analysis of hard rock pillars, and indirectly in synthetic rock mass models to determine rock mass strength, is the actual stress level and stress path imposed on the pillar due to the excavation sequence and the location of the pillars within the mine layout.

Read the paper to learn how the authors used numerical stress analysis to determine how stresses vary across the excavated pillars in a typical room-and-pillar mine layout, and thus generate a spatially variable determination of pillar stability.

Eurock PLAXIS Paper Hard-Rock Pillar

Figure 1: (a) Mine lay-out and selected pillars use in the analysis; and (b) 3D stress model created in PLAXIS.

PLAXIS 2D and 3D Results Yield Better Analysis 

Because of the computational difficulty associated with hybrid modelling of realistic discrete fracture networks, synthetic rock mass modeling is commonly carried out using PLAXIS 2D. By comparing 3D and 2D results for selected cross sections across, the authors believe the results of the analysis will provide the opportunity to better constrain the stability implications of a 2D approach to pillar design and synthetic rock mass modeling.

Read the paper

Co-authors Sandro Brasile, Senior Manager of Geotechnical Research at Bentley, Giuseppe Cammarata, Ph.D., P.Eng., Research Product Manager at Bentley, and Davide Elmo, Associate Professor (Rock Mechanics), Ph.D., P.Eng., University of British Columbia, NBK Institute of Mining Engineering, recently wrote a paper for the Eurock 2021 conference, Numerical Analysis in the Study of the Behavior of Hard-Rock Pillars.


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