J-Block: Tabular excavation support design by optimizing rockfall risk
J-Block: Tabular excavation support design by optimizing rockfall risk
Embedded Files
J-Block method
J-Block method
J-Block uses stochastic keyblock analysis to evaluate joint defined block stability in tabular excavations
Block release and block sliding modes are evaluated and the effect of support is considered.
Support models include elongate timbers, packs (cribs), rock bolts and temporary jacks.
Joint-formed blocks exposed along advancing face
Joint-formed blocks exposed along advancing face
Blocks formed from joint statistics
Each block tested for potential failure using keyblock method
Stabilizing effect of supports calculated
Countour plot of rockfall hazard based on 32,000 block samples
Countour plot of rockfall hazard based on 32,000 block samples
J-Block considers thousands of potential blocks and their stability to create a contour plot of fall hazard in a stope
Statistics provided of blocks that fall out between supports, blocks that fail the supports, blocks that are stabilized by supports.
Defining excavation outline and supports
Defining excavation outline and supports
Simple 2D graphics to define stope outline
Supports are located by mouse clicks and can be dragged around stope
Supports installed as grids, lines or single units
Random variation of exact location of supports can be defined.
Input of joint set data
Input of joint set data
The joint set input screen allows up to six joint sets to be entered plus a random set
For each joint set the friction, cohesion, trace length and orientation data are required
Results summary
Results summary
Summary of rock falls for each mining step simulated
Hazard calculated for different zones within the stop
Results histogram
Results histogram
Shows block size distribution with failure modes
J-Block analysis methods
J-Block analysis methods
J-Block makes use of joint set statistics and the Keyblock method (Goodman & Shi, 1980) to simulate a large number of potential blocks in an excavation surface.
Statistics are kept of the number of potentially unstable blocks, the volume of failure, safety factors etc., which allow you to evaluate the relative stability of different mining directions or stope layouts. The program automatically looks for combinations of different joints and checks for potential sliding or block release failure modes.
Various support systems can be defined simulating timber supports, packs or cribs, rockbolts and props with headboards. Support characteristics such as dimensions and capacity are user defined.
The program located blocks at random locations behind the advancing face and determines whether any supports are present to stabilize the block. Support failure or failure between supports is possble. The length of rock bolts and anchorage length are considered. Rock bolts can fail by the grout pulling out, failure of the steel or by being too short to protrude the block.
The risk of injury is calculated on a stochastic basis using the potential exposure of personnel and their working areas. An injury is assumed to occur if a rockfall coincides with the location of a person.
Output is presented as easily interpreted "volume of failure" and risk values. Other outputs are also provided such as failure probabilities and safety factors.
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