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|The portal, which is the near-horizontal, surface point of entry to an underground excavation, can often be an exceedingly difficult area in terms of ground control. Surface and subsurface failures at portals, as discerned during a study involving over 300 case histories, are unfortunately, common. To aid in the engineering evaluation of portals, the Geomechanics Classification System was appended with discontinuity orientation assessment values and support/excavation guidelines. Also, a design model utilizing RMR predicted rock loads in conjunction with half-dome theory is proposed for the most common type of portal failure. Other pertinent comments and recommendations relating to portal stability are included.|
Additional chapters/articles from the SME-ICGCM book Rock Mechanics as a Guide for Efficient Utilization of Natural Resources
|Rock Mechanics And Ground Control For Underground Mining And||Underground Storage, With Emphasis On Storage In Excavated R||Rock Classification For Portal Design||Laboratory And Field Characterization Of Immediate Floor Str||Comparative Study Of Western US Longwall Panel Entry Systems||Supercomputer Assisted Three-Dimensional Finite Element Anal||DEPOWS - A Powered Support Selection Model||A Study Of Displacement Field Of Main Roof In Longwall Minin||Cavability Investigation Of A Stratabound Copper Deposit, To||Influence Of Discontinuity Orientations And Strength On Cava||Premining Stability Analysis Of A Shaft Pillar At The Homest||Identification Of Critical Slope Failure Surfaces With Criti||Improving Design Methodology For Innovative Rock Mechanics D||Stability Evaluation Of Alternative Designs Of Drift-And-Fil||In Situ Stress For Underground Excavation Design In A Natura||Application Of Physical And Mathematical Modelling In Underg||Complex Seismic Trace Attributes In Coal Exploration||Changes In Seismic Measurements With Blast Induced Fracturin||Changes In The Seismic Properties Of The Cover Produced By L||Crosshole Seismics: Applications In Mining||Geotechnical Mapping By Seismic Imaging In Underground Mines||Experimental Study Of Line Electrode Method To Detect Underg||Time-Dependent Behavior Of Rocks: Laboratory Tests On Hollow||Pillar Sizing||An Applications Approach To Barrier Pillar Design For Improv||Yield Pillar Application Under Strong Roof And Strong Floor||Methods To Determine Pillar Stress Distribution And Its Effe||Correlation Between Unconfined Compressive And Point Load St||Study Of Coal Fragmentation Under Conical Bit Indentation||Development of in-situ stress measurement technique using ul||Understanding the hydraulic pressure cell||Development of a mechanistic model for prediction of maximum||Subsidence prediction using a laminated linear model||Subsidence and environmental impacts in Japanese coal mining||Surface damage due to longwall mining - A case study||Pre-mining stresses at some hard rock mines in the Canadian||Estimation of in-situ material strength||The research on the mechanical properties of hard roof in un||Relationship between the clay fabric of roof shales and roof||Failure mechanisms in ultra-close seam mining||An analysis of roof-pillar-weak floor interaction in partial||Finite element analysis and comparison of shaly mine roof su||Stability analysis and characterization of ground subsidence||Subsidence monitoring at a shallow partial extraction room-a||Assessment of surface fracture depth and intensity due to su||Prediction of surface movement with emphasis on horizontal d||Numerical simulation of coal pillar loading with the aid of||Three-dimensional FEM analysis to sale field measurements fr||Front abutment effects on supplemental support in predriven||Direct determination of failure surfaces in earth slopes||Hydraulic stowing - A solution for subsidence due to undergr||Research on the rational structure of tensible rockbolt and||System behavior analysis of the ground movement around a lon||CISPM - A subsidence prediction model||Dynamic rock anchors||Ropes mine crown pillar rock mechanics||Deformation and failure-time prediction in rock mechanics||Influence of joints on the elastic response of a LFUFL stope||Support selection of mine roadways by means of a computer pr||Theoretical analysis of breaking strength of mine pillars an||A comparison between two- and three-dimensional numerical mo|