In Situ Stress For Underground Excavation Design In A Naturally Fractured Rock Mass

Hyett, Andrew J.
Organization: International Conference on Ground Control in Mining
Pages: 8
Publication Date: Jan 1, 1989
The ISRM commission on testing methods has recently presented Suggested Methods for rock stress determination (Kim & Franklin, 1987). This proposes that even if the magnitude of in situ stress is not sufficient to cause significant ground problems, the optimum shape, orientation, and layout of underground structures can be significantly affected by it. In the design of underground excavations, the engineer often requires a knowledge of the average in situ stress tensor in the rock mass. However, attempts to measure a stress state applicable to design have proved frustrating, and a high degree of uncertainty is introduced by the variability in results. In the belief that deduced fluctuations are random in nature, many separate measurements are often made, so that a more reliable stress tensor average, and some indication of the associated variance (see Dyke et al., 1986) can be calculated. Unfortunately, this approach is limited by economic considerations and, as with any sampling procedure, it is imperative to understand the sources of measured variability, in order to design an optimum measurement programme. Cundall(1987) itemised the main causes of stress variability as a. Instrument and measurement errors, and b. Natural fluctuations of stress from point to point, induced by the action of a boundary stress on the internal rock structure. At least four categories exist: i. inhomogeneous rock, bedding, intrusions etc.; ii. differential contraction, creep, or changes in rock properties with time; iii. proximity to faults or discontinuities; iv. cycles of tectonic activity that cause movement on joints. The latter was successfully investigated using the distinct element programme UDEC. In this paper, the contribution of items (iii) and (iv) (i.e. the items related to discontinuities) to the total stress variability will be discussed, for the kind of rock mass shown in Figure 1. Although many authors have concluded that rock joints have an influence on the stress in their vicinity, a more analytical approach is required if the stress distribution associated with different jointed rock masses is to be (i) compared, and (ii) related to routinely measured joint parameters. If this can be achieved then, prior to any attempt to measure stress in a jointed rock mass, a consideration of joint geometry, joint deformability, and the geological kinematics of joints (e.g. the magnitude and direction of previous movements), can place valuable `common sense' constraints on the expected stress system for minimal extra cost.
Full Article Download:
(2328 kb)

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